INTRODUCTION TItIS paper compares the interactions of two species of plovers usually placed in separate genera (A.O.U. Check-list, 1957) with two species of sandpipers usually put into the same genus (A.O.U. Checle- list, 1957). The 1954 Bylot Island Expedition spent from 12 June to 29 July at the mouth of the Aktineq River, at approximately latitude 73 ø N, longitude 79 ø W, in southern Bylot Island. Bylot is between the Low and High Arctic just north of Baffin Island and south of the eastern end of Devon Island. A short description of the expedition has been published by the Drurys (1955), and a lively, popular account is given in Scherman (1956). A map showing the study area and locality names appears in Scherman and in Miller (1955). Faunal details and descrip- tion of the study area have been published in Van Tyne and Drury (1959). Observations were made by William Drury, Mary Drury, and Ben- jamin Ferris, who concentrated on the breeding birds; and by Josselyn Van Tyne, who gathered information in daily collecting trips outs!de the study area. A field map (Figure 1) shows localities in our study area. A vegetation map (Figure 2) shows location of nests. The expedition was supported by a private grant and by the New York Zoological Society. Arrangements were made through the Arctic Institute of North America. I prepared this report while on sabbatical half-year at Harvard University in 1955 and nmde extensive revisions while with the Massachusetts Audubon Society. Josselyn Van Tyne's illness and death prevented the preparation of a combined report and delayed the publication of this material, but we were able to report several of these conclusions at the American Ornithologists' Union meeting in Boston (Van Tyne and Drury, 1955). I. ECOLOGY AND DISPLAYS AMERICAN GOLDEN PLOVER Pluvialis dominica (Milllet) (Eskimo: To6dlee-hr/ttsuk) We could easily differentiate the sexes because the face and under- parts of the males in our area were almost solid black, whereas in the ? 3/4 ,o .?o Figure 1. Field map of the study area. female they were mottled with gray and xvhite, and the white areas on the sides of the chest ahnost met. Golden Plovers were display-flying on Bylot Island when we arrived the evening of 12 June. We saw a flock of 90 to 100 flying rapidly southeast on 15 June, and 96 on 16 June flying north. Habitat and density. The two nests of Golden Plovers in our study area (Figure 2), the 13 pairs at Ooyarashukjooeet, and the six pairs near Oonakuktooyuk were on the general tundra vegetation of mosses (Hypnaceae), sedges (Cyperaceae, Juncaceae), grasses (Trisetum spicatum [L.] Richt., Poa rigcns Hartin., and trctagrostis latifolia JR. Br.} Griseb.), Avens (Dryas integrifolia M. Vahl), and Arctic Willow (Salix arctica Pall.), where mat plants alternated with small C BARREN :': DRY MAT PLANTS B WET MOSSY VEGETATION 'A' BAIRD'S SANDPIPER '' NEST NOT FouND, O WHITE-RUMPED SANDPIPER O NEST NOT FOUND ß BLACK- BELLlED PLOVER ß . GOLDEN PLOVER '' OLDSQUAW % SNOW GOOSE Figure 2. Vegetation and nests. The major types of vegetation in the study area are mapped. Symbols of the nest locations show the correlation of sites with vegetation. patches of bare soil. hi these places, (;olden Plovers were on fine- grained soils disturbed by frost action into polygons and terracettes (Washburn, 1956). :X_t Oonakuktooyuk, the slopes were so disturbed by slumping that the bare areas on the tops of the terracertes were larger than the mats of vegetation. We found Golden Plovers on south-facing areas below 150 meters from which the snow disappeared early. All territories were within two miles of the coast. Seebohm and Harvie-Brown (1876) reported this species nesting on exposed, rounded hilltops in the Petchora Valley; in western Alaska, Walkinshaw (1948) found one nest in a damp spot of tundra on a mound surrounded by sedges, another on "much higher, completely dry . . . land." Any comparison of nesting sites involving a large geographical area lnUSt alloxv for regional differences of vegeta- tion. Full, accurate descriptions of vegetation are usually not available. Nearly all sites at Bylot Island were dry, in comparison with those studied by Walkinsbaw in Alaska. Territory. In display flight over Plover Plateau (Figures 1 and 3), a bird flew with hesitant flight like that of a Nighthawk (Chordeiles minor) or the fish flight of a Colnmou Tern (?terna hitundo), calling ktoddlee ktoddlee. It flew in either direction, or in "figure 8's." fronl Loon Pond to Iceberg Lake. A second flight pattern overlapped with this--over Tui-Tui Tabletop west to the West Ridge. We did not see two birds in the air at once, and we saw 11o conflicts. Walkinshaw (1948) reports a similar flight ending with a sudden drop almost to the ground, then a quick rise to pass far out over the tundra. At times we heard only a kleeeee given every 20 seconds, but when the bird came closer, we heard a fainter rood preceding the louder note. Displaying birds flew with their wings held largely above the horizontal. There was a slight hesitation at the highest point and a longer hesitation at the end of the downstroke (Figure 3). Tlmse flights were most frequent and Ion.';-est on 12-15 June; and last recorded on 6 July. The usual times were 2100 to midnight and early in the morning. ,4!7!7ressiz'c behavior. The parents at uest No. 2, on intrusion of a male Black-bellied Plover, took the FOSture described in Table 1 (Ag- gressive on Ground). On 30 June at nest No. 1 the alarm cries of a pale bird brought up a dark bird, but when the dark bird (presumed male) came to within 30 meters, the "female" suddenly turned and drove him away. This may have been because he was uot her mate or because she was confused and overexcited by me. As Williamson (1947) and Moynihan (1955) have suggested, the tendency to drive away the hulnan intruder is re- directed to a substitute that will flee. When attacked, the male ran away a short distance, then both birds stopped. Again she ran at him, head down and back feathers ruflted, crying ttirdileee and kleeJar,. then flew at him with head stretched out in front, calling eeeeeooooo-eeeee- ooooo tswit-tswit, ceeeeooooo-eeeeeooooo eeeeeooooo-eeeeeooooo, or kloo twit-tswit kloo. At each cry of tswit-tswit, the pursuer bobbed her head vigorously. Sometimes she pursued him in a short, rapid zigzag. He flew; she caught up and glided past while he flew on; she lit and he lit near her, and they repeated the "leap-fro.-" performance. When FLEEING DISTRACTION AGGRESSION PURSUIT OF BLACK'BELLIEDPLOVER Figure 3. Golden Plover displays. they landed. they held their wings over their backs and ran a few meters (Figure 3--ground pursuit). The colors of the axillars in the two closely related species of Pluvialis suggest that this posture, holding wings over the back, has "signal" function. During a group flight over the uplands at ¸oyarashukjooeet on 12 July: (1) one bird flew in a meandering course over a circumscribed area, while another repeatedly flew from behind, set its wings at the limit of the upstroke, and coasted past, calling toodleka-toodleJka, bobbing its head violently; (2) two birds on one occasion and three on another, pursued each other with rapid zigzagging, hairpin turns, steep dives, and towering climbs, swerving and spreading their tails. They spread their tails simultaneously many tinms during the flight, even when flying straight. They called tsee-wiPwit-tsee or tswit tswit. We heard these calls only when a Golden Plover was driving away another Golden Plover, a Black-bellied Plover, a Parasitic Jaeger (Stercorarius parasiticus), or a Long-tailed Jaeger (Stercorarius Ion9icaudus). These displays resenable those described for the European Golden Plover (P. apricaria) by D. Nethersole-Thompson (Witherby, et al., 1940). tppeasement display. On 22 June I watched a presumed female at the mouth of Golden Plover Creek. A second bird flew' down from the plateau and lit about 20 meters away, thn xvith head lowered and shoulders hunched, ran a short way toward the female with his wings raised, folded his wings and ran forward again. When he was about one meter away he cried w//-/t very rapidly, then stood with his head and neck stretched upward (Figure 3, male). The other bird remained motionless, with head raised (Figure 3, female), then took a few- slow steps and pecked the ground, and took a few more steps. The new bird followed for a few- moments, then they moved apart, feeding. Nest and e##s.  The three Golden Plover nests that we found (mapped in Figure 2--dry mat plant areas) were in slight hollows surrounded with scattered mat plants. From date of hatching of our earliest nest, the clutch (4) was COln- pleted between 18 and 20 June. The first egg was probably laid on 13 June. In some Golden Plover eggs there is a greenish tint to the back- ground color in contrast to the pastel gray of the Black-bellied Plover, but our examinations in the field and in egg collections showed no reli- able way of distinguishing the eggs of the two species. tctivities during incubation. At nest No. 1 the female (judged by plumage) was nearly always at the nest, and we rarely saw- the male during nest-checking rounds. We have moving pictures of the dark- plumaged bird performing distraction displays, however, and know that both members of the pair stay close to the nest during incubation. Allen (1934) reported that both parents incubated at Churchill, Mani- toba. Walkinshaw (1948) reported that in "Pacific" Golden Plover (Pluvia[is dominica fulva), both parents incubated. My experience  Detailed descriptions of nests of the plovers and the sandpipers are available at the Hatheway School in South Lincoln, Massachusetts. These descriptions include elevation, location and description of site, details of the surrounding vegeta- tion, and materials used in the scrape. They also include the daily observations, date of finding, and times of hatching. 182 DRmt3/4, Breeding Biology of Shorebirds [ Auk [ Voh 78 Aprill DRtRV, Breed&to Biology of Shorebirds 183 1961 l 184 DRUR3/4, Breeding Biology oJ Shorebirds [ .Auk - [ Vol. 78 with the European Golden Plover in iFinland indicates that both sexes incubate. Hatching and care of the young. The eggs in nest No. 1 hatched 15 and 16 July. One egg in nest No. 2 pipped 20 July, three hatched 22 July; all by 24 July. We found two youug and their parents on 17 July in the marsh at the northwest corner of Plover Plateau xvben the young of nest No. 1 were at Loon Pond. The young stayed in the nest until all eggs hatched; then all four left, but returned to the scrape the first night, presumably to be brooded. On the following day they moved to marshy places. Both parents accompanied the young for at least two weeks. For a discussion of the plumage of juvenals, see Van Tyne and Drury (1959). Reactions to predators. D. Nethersole-Thompson (Witherby, 1940) said that injury feigning is not common in the European Golden Plover, but we found it commonplace and conspicuous at Bylot Island as soon as clutches were complete, as did Williamson (1948). My experience with European Golden Plover in Finnish Lapland in 1958 was that they cried noisily, but did little distraction display. For distraction display at various levels of concern see T'able 1. Between distraction displays the bird ran, pecked stiffly and called khlleeeeeooo in alarm. As it circled it often ran in closer, when it was behind us with the sun behind it. There was a complete gradation of intensity from the early alarm call at leaving the nest to the violent wing flopping. At both nests the dark-plumaged birds (presumably males) consist- ently were more shy, performed less-intense distraction displays, and remained at a greater distance. After watching a pair near Oonakuk- tooyuk for 10 to 15 minutes on 20 July, I shot the dark-plumaged bird, and it was a male. When the bird rushed at us and threw its breast int6 a holloxv with wings spread, it closely resembled postures illustrated by Hosking for Avocet (Recurvirostra avosetta) in Simmons (1955) and for Killdeer (Charadrius vociferus) by Deane (1944). BLtCK-BELLIED PLOVER Pluvialis sqttatarola (Linnaeus). (Eskimo: To6dlee-hrfitsuk) The Eskimos called this species by the same name as the Golden Plover, although they recognized two different species. Reasons for including sq,tatarola in Pluvialis are given below (Behavior and Sys- tematics), and in Van Tyne and Drury (1959). Males were in full, dark-breasted plumages; females were much less fully spring plumaged and varied in the amount and position of black patches and speckling. The female at nest No. 3 showed no black below. We first saw this species on 17 June at camp, and never saw flocks. We heard the typical fall cry, keleeeo& first on 22 July from a bird flying south over the Aktineq. Habitat and density. Sutton (1932) and Brandt (1943) speak of the exposed nature of the Black-bellied Plover's habitat, remarking that they nested on high, exposed ridges. Four nests and two territories near camp (Figure 2), two pairs east of the Aktineq, 10 July, three pairs at Ooyarashukjooeet, 14 July, and two territories near Oonakuk- tooyuk, 20 July, were all associated with the driest, most exposed ridges, river banks, or raised beaches, within a mile of the sea. These areas were among the first to be free of snow. and were char- acteristically on sand or gravel scattered with cobbles and black lichens, clumps of Grass Rush (Luzula confusa Lindeb.) and Gray Lichen (Stereocaulon paschale [L.] Ach.). There was a sparse growth of mat plants (Arctic Willow, and Bell Heather, Cassiope tetragona [L.] D. Don), and clumps of Alpine Sweetgrass (Hierochloe alpina [Sw.] R. & S.), Poppy (Papaver radicatum Rottb.), and Purple Saxifrage (Saxifraga oppositifolia L.). Seebohm and Harvie-Brown (1876) report the nesting of Black-bdlied Plover on peat ridges in wet marshes, and Walkinshaw (1948) reports a nest on a mound on a flat above a lake. (In western Alaska the term "flat" usually refers to a compound peat bog of great extent.) Territory. We saw display flight and ground displays 19 and 20 June near Loon Pond. The flying bird stayed at about 30 meters above the ground, flapping slowly and hesitantly as does a butterfly (Simmons, 1953), or a Short-eared Owl (,4sio fiarnmeus)--(Figure 4). The displaying bird flapped more slowly and had a shorter hesitation at the top of the upstroke than a Golden Plover. It called kehweh, or kadilo& like its own fall cry, but with the quality of the call of a European Curlew (Nurnenius arquata). The first and last syllables were accented, and were longer and lower than the middle syllable. At the end of the slow flight, the bird suddenly flew very fast, swerving and towering, and occasionally dashing at the ground. We have often seen diving flight, on spring migration, and it has been reported by Seebohm and Harvie-Brown (1876), Haviland (1915), and Sutton (1932). At 2330 on 3 July a Black-bellied Plover was still slowly display flying over Tui-Tui Tabletop and the Little River, calling koddleeeod about once a minute. ,4ggressive behavior. The Rosins (Drury and Drury, 1955) de- scribed Black-bellied Plovers on 19 June endlessly running past each other--one with head lowered, the other with head raised. This may DRURY, Breedin# Biolo#y of Shorebirds FLY DISPLAY FLIGHT LOW-LEVEL DISTRACTION BEHAVIOR HIGH-INTENSITY DISTRACTION BEHAVIOR RETREAT  STANDING NEAR NEST ACTIONS AT GOLDEN PLOVER NEST 187 Figure 4. Black-bellied Plover displays. be similar to behavior of Goldeu Plovers described by Williamson (1948). Birds at the uest "directed" similar running at an intruder, which suggests aggression (Simmons, 1955). The male at nest No. 4 briefly redirected hostility toward his mate. tie ran at her with head down, calling kle;ear. She ran to one side with head held very high (see Competitiou between Black-bellied Plover and Golden Plover under Ecological Interactions). I have seen aggressive postures among birds in breeding plumage on fall migration in August in Massachusetts. At its most intense expres- sion, when "stauding off" an opponent, one bird bows deeply with head stiffly held dowu in line with the body, back ruffled, tail fauned tld raised, breast feathers fluffed. The birds may crouch in this posi- tion and then, standing stiffly, peck at the ground and flick pebbles or bits of weed over the shoulder. They may edge around each other, crouching and bowing, wrists partly lowered and tail canted and mostly spread; then they stop and flick pebbles again. When aggressive, migrant birds move toward an opponent, they stalk stiffly, suggesting differences from the actions the Rosins described. Much more detail is needed. Nest and eggs. The four nests that we found (Figure 2) were all in bare areas among widely scattered patches and clumps of plants. We found a nest with three eggs on 30 June. In this and two other nests, eggs hatched 26-29 July. In another nest, eggs hatched 22-24 July, which suggests that the first egg was laid about 20 June. Clutch size was four in all nests. ,4ctivities during incubation. At the nests studied, the male did almost all the incubating, but we saw the female near nests Nos. 1, 3, and 4 repeatedly. At nest No. 3 the female stayed in a sedgy marsh about 100 yards away and occasionally approached the nest when in- truders came. On one visit after a long disturbance the male returned to incubate, but an hour later the female was on the nest. The female as well as the male incubated at nest No. 1. In 15 visits to each nest we found both birds absent two or three times for each. Shyness may have made the parent (female?) leave so early that the nest checker missed it. Pickwell (1942) called such action "casual abandonment" and sug- gested that it is of survival value in concealing the nest of Prairie Horned Larks (Otocoris alpestris praticola). Hatching and care of young. The last egg in nest No. 1 was laid on 1 July or early in the morning on 2 July; it hatched the night of 27 July or early on 28 Jiffy--one day after two others, and two days after the first to hatch, 26 July. Incubation period was 26 days (or almost 27 days). One egg in nest No. 2 hatched 27 days after the nest was found. Several eggs pipped two days before hatching. The eggs hatched over a two-day period, 23-24 July in nest No. 3 and 28-29 July in nest No. 2. Nest No. 4 had not hatched, but two eggs had cracked when we left on 29 July. Brandt (1943) reports an incubation period of 23 days in one instance in Alaska, but without details. Dementiev et al. (1951) report that the incubation period is unknovn. H6hn (1957) reports the hatching of one egg 24 days after completion of the clutch on Banks Island. My experience with Killdeer suggests that the incubation period can be lengthened two days if the nest is regularly visited. The young spent one night in the scrape after all had hatched. We have no observations of parents with young away from the nest. Reactions to humans. Black-bellied Plovers were extremely shy at the beginning of the incubation period. I found the first nest on 30 June accidentally while studying frost features through binoculars. The male, sitting on this nest, left it as soon as we appeared, over 200 meters away, and ran very fast with head down, for 75 meters, along a frost crack. At that distance he stopped, looked up, called, and flew away. On 2 July the clutch was completed, and we saw the first dis- traction display--running in a crouch with the near wing' lowered. The birds at nests Nos. 1, 2, and 4 would not come within 100 meters until the last week of incubation, while the male at nest No. 3 showed marked concern more than two weeks before hatching'. Toward the end of the incubation period, the male left the nest when we were ahout 100 meters away. When the eggs pipped and cracked in nest No. 1, the parents came within two meters to display. T'le tess-aggressive bird at all nests was markedly less full plumaged. On leaving the nest, the male usually flew to a high ridge and watched us, occasionally calling gleee or keeku-kudle?ah. The usual cry from the nest was koodle. If the intruder withdrew, often he returned to the vicinity of the nest and seemed to settle on eggs. The male at nest No. 3 did this three times within 30 meters of the nest while we were waiting for him to return, and at one place spent 27 minutes in rather "disinterested" preening after seeming to have settled on a nest. For details of the several levels of intensity of distraction behavior see Table 1. The circling bird regularly came closer when behind and against the light. Occasionally he rushed in (presumably aggressively), showing a maxinmm of white, holding his head down, back feathers ruffled, and tail cocked and partly spread; occasionally he spread his wings wide on this run. At nest No. 3 the female stood and flapped her wings slowly (very much like the distraction display of a Golden Plover) while the male was running in close with wings spread and head thrust forward. The pair ran tongether in an arc, he with head lowered, she with head raised. Reaction to jaegers. A Black-bellied Plover dashed at a Parasitic Jaeger hovering over a loon (Gayla stellata) nest 30 June, flying very fast, calling kidIoOeeeod, and chased the jaeger up the Aktiueq River. In July Black-bellied Plover males Nos. 1 and 2 drove Long-tailed Jaegers away from their nests, as Brandt (1943) has described. RINGED PLO FER Charadrius h. hiaticuIa Linnaeus (Eskimo: Ko6dlee-koodleah) The population that we studied was part of the Old World C. h. hiaticula. We have indicated (Van Tyne and Drury, 1959) that we agree xvith Bock (1958, 1959) that the New World population is the same species as the Old World Ringed Plover. The former, however, raises the white feathers of its throat conspicuously in threat behavior on migration, while the broad breast band of the European race seems to be emphasized by that population. This needs further study,, We found this species on gravel pavements, which the prevailing east wind kept nearly free of vegetation, on a hilltop east of the Aktineq, on gravel bars at the Aktineq and at Ooyarashukjooeet, and on thinly vegetated cobbles of an old beach deeply scarred with frost cracks, 50 meters above sea level at Oonakuktooyuk. The sites agree with those reported from central Baffin Island (Wynne-Edwards, 1952), and from southern Baffin Island (Sutton and Parmelee, 1956) for C. h. semi- palmatus. Display flight. We saw Short-eared Owl-like flight at Ooyarashuk- jooeet on 14 July and at Oonakuktooyuk on 20 July when we entered a territory. Many times we heard birds in the air and on the ground calling trh-rick tchi-rick more and more rapidly until the call became a steady rattling that ended suddenly on a descending slur. Soper (1928) and Sutton and Parmelee (1956) described this as the flight song of C. h. semipalmatus. Simmons (1953, 1955) pointed out that flight song may be found as low-intensity distraction or hostility dis- plays. The call is common on fall migration when birds are threatening. Aggressive postres. The female collected 14 July showed moderate concern and was not the bird that performed the owl-like flight or that suddenly flexv in close and stood with head held high, breast fluffed out (described by Edwards et aI., 1947, as an aggressive display). Usually the cries of birds disturbed on their territories attracted one or two neighbors that stood and called nearby, as Mason (1947), and Sutton and Parmelee (1956) reported. Distraction display. When running, the birds seemed to try to put themselves on the side of the intruder away from the chicks, as Ledlie and Pedler (1938) suggested for the Little Ringed Plover (Charadrius dubius). Simmons (1952) wrote that sernipalmatus, in areas where there is less fear of humans, direct the distraction display to, or at right angles to, the intruder; while hiaticuIa direct it axvay. FHITE-R UMPED SINDPIPER Heteropygia fuscicollis (Vieillot) (Eskimo: Livilivilak) Reasons for reinstating Heteropygia are given below (Behavior and Systematics). We heard no calls that resembled llviIivilak. Thus, the Eskimos' name seems to be name transfer from Semipalmated (Calidris pusillus) and Least Sandpipers (Calidris minutilla), which have such a call, and are named "livilivilak" by the Eskimos of Baffln Island, Southaml)ton Island, and Melville Peninsula. Bylot Island, together with Arctic Bay, where Shortt and Peters (1942) collected juveniles, seems to be the northeasternmost recorded breeding of White-rumped Sandpipers. We saw no bird of this species, until the general arrival on the after- noon of 19 June. Habitat and density. White-rumped Sandpipers nested in the mossy hummocks in marshes, or in the mossy depressions in cluml)s of grass and sedge in the uplands (Figure 2--wet mossy). This habitat was under snow until about 15 June and, being protected by a snow blanket, had a uniform environment where mosses survive. At least six pairs nested in our study area (mapped on Figure 2). We saw- none else- where except at a large creek three miles north of camp on 26 June. Territo2v. Sutton (1932) described most of the actions except ground display. Displays were conspicuous on the afternoon that the species arrived. In display flight the bird flew with ordinary xvingbeat to a height of 15 to 25 meters, and there changed to a shallow wingbeat like that of a Spotted Sandpiper (.4ctitis mactlaria). The bird held its head up and neck stretched out, giving a song sounding like a fish reel running, or, as Sutton puts it, a typewriter carriage. Inserted into this song were two or three sequences, during which the bird violently ex- tended and drew back its head. It called ng-oik six to 10 times in suc- cession, sounding like a small pig; n 9 with head hunched in, and oik with head up and neck stretched (Figure 5). At the end of the display the bird set its wings above the horizontal and glided to the ground-- silently, calling zip-zip, or giving the fish-reel song. As it landed, usually near another bird, it folded its wings, then slowly stretched the wing nearest the other bird straight over its head. The single-wing display was much less well developed than in Baird's Sandpiper and in the Purple Sandpiper (Calidris maritima) described by Keith (1938). On the other hand, flight displays strongly resemble that of Pectoral Sandpipers (Heteropygia melanotos), as described by Witherby et al. (1940) and Pitelka (1959). On 20 June we watched for about 12 minutes two birds (presumed to be males) fight in the presence of a third (presumed female). The males rushed at each other with head lowered, back feathers ruffled, but wings not spread. They flew up 15-25 cm. (6 to 10 inches) to peck and beat each other with their wings, land, and chase, sometimes chasing each other with wings spread and tail partly cocked. Finally one flew away toward camp; the other followed to the edge of Golden Plover Figure 5. White-rumped Sandpiper displays. Creek where it trilled, returned, and landed abruptly near the third. We saw and heard no song displays or territorial disputes after 30 June. We saw conflicts at two territorial borders: the marsh on the upper edge of Plover Plateau; and the fiat east of the mouth of Golden Plover Creek near Loon Pond on 20 June. However, by the time the young of nest No. 4 had hatched (north of Loon Pond), territories as such had been abandoned and both young and parents trespassed unmolested. Cortship. 1. Flight. On 21 June one bird chased another, set wings like a pigeon, and glided past, calling n#-oile, then banked and turned sharply on set wings (Figure 5). The pursued flew oi in a semicircle from near Loon Pond up over Kungo Hill, and the pursuer repeated the action several times. Over Kungo Hill, a bird from the West Ridge joined, and the three flew together for about 15 seconds with no conflict. Then the pursuer from Loon Pond returned, and the newcomer (a second territory) displayed on canted wings, calling like a pig, and the chase went on over Plover Plateau. A third territory and route vas from the Upper Phalarope Ponds, up Golden Plover Creek to the marsh at the head of Plover Plateau. The behavior of these males, vhen females passed through their territories, suggests modification of court- ship similar to that described by Pitelka (1959) in Pectoral Sandpipers: i.e.. that there is no persisting pair bond and females may nest without regard for any male's territory. We found two nests where there was one male--on the two sides of the mouth of Golden Plover Creek. 2. Ground. Ground displays resemble those of the Sharl)-tailed Grouse (?edioecetes). The displaying bird gave a constant twitter-- bzzzzzzzzzzzz; lowered his head, cocked his furled tail straight up (making the white rump conspicuous), spread his stiffly held wings to the side, dragging their tips on the ground, and rapidly stamped his feet. (We have no proof of the sex, and possibly the role of the sexes might be reversed.) In this position the displaying bird glided around after the (presumed) female, facing her (or side to her), sidling around her in a semicircle. Every now and then he raised the wing that was toward her when he was running along beside her. Several times he raised t;oth wings (without stretching them), and tilted and spread his tail toward her. She stood with her head up and occasionally briefly raised the wing on the side toward him. She walked nervously, but stopped if she got more than two meters away. When she moved, he stopped displaying, ran up to her side, and started to sidle around her again. The action stopped suddenly, and the two birds stood idly, or the female suddenly flew off. When she flew, he pursued her in a mad dash over the marsh and hillsides, chiefly in long, straight flights, but occasionally with sharp zigzags. Displaying was interrupted repeatedly for periods of 15 minutes to an hour, during xvhich time the birds appeared to feed. Nest and eggs. The nests were in a mossy clump iu grasslike growth. The grasslike plants growing near the nests we found included Narrow- leaved Cotton Grass (Eriophor,m angustifolit,m Roth), Grass Rush, Water Sedge (Carex aquatilis Wahlenb., vat. stans [Drej] Boott), or Arctic Redtop (,4rctagrostis latifola [R. Br.] Griseb.). The moss was usually Bog Moss (,4dacomnum ? pahstre [Hedw.] Schwaegr.), but also other Hypneaceae such as Broom Moss (Dicran,m sp.), Twisted Moss (Tortella sp.), Shining Moss (Tomenthypmm niteus [Schreb.] Loeske), and Gray Moss (Rhacomitrium ? langinosum [Hedw.] Brid.) --(Figures 2, 5). The clutch in our earliest nest must have been com- pleted by 25 or 26 June (Table 2); so that if eggs are laid every other (lay, egg laying must have started two days after the species arrived. This remarkable adaptation to arrival under rapidly changing condi- tions, yet exactly timed for proper breeding, should be further docu- mented. Hinde (1951) and Nisbet (1957) have commented on the accuracy of timing of shorebird migration with the breeding cycle. Clutch size was four in all nests. TABLE 21 NEST DATA--WltlTE-RUMPED SANDPIPER Date found and contents First egg No. of young Nest No. on that date Location hatched produced 1 28 June (4 eggs) Loon Pond 15 July 4 ( 1 collected) 2 3 July (4 eggs) Lower Plover 22 July 4 Plateau 3 7 July (4 eggs) Upper Plover 20 July 4 Plateau 4 12 July (4 eggs) Phalarope Ponds 15 July 4 Brood 5 20 July Northwest 4 Tui-Tui Tabletop 6 25 July Upper Phalarope Ponds been Nest No. 2 7 25 July Southeast 4 Tui-Tui Tabletop This form of table was used by DuBois (1936, 1937); Parmelee (1954, 1956, etc.) in their Baffin Island studies. and by Sutton and Activities during incubation. During the last two weeks of incuba- tion, we found only one bird near the nest, and that bird reacted uni- formly to intruders. Earlier, a bird loafing on the edge of the territory sang and took part in flight song on several occasions. In our nest- checking rounds we found no birds on the nest in 3 of 16 visits to nest No. 1; in 3 of 12 visits to nest No. 2'; in 3 of 9 visits to nest No. 3. These suggest that birds spent 20 to 30 per cent of the time away from the eggs during the day when we made our rounds. When we waited for the parent to return, it came back fast and directly, not as if it had been frightened from the nest by our approach. Alternatively, the bird of one sex may have been frightened by us at a great distance and the other sex was returning hurriedly, having responded at meeting that lzird. Sutton's (1932) evidence from collected birds indicates that only the female incubates. We presumed that the "loafing" individual was the male. Pitelka (1959) found that male Pectoral Sandpipers take no part in incubation, and Portenko (1959) reported the same in the male Curlew Sandpiper (Calidris ferruginea). When the bird returned, it entered the scrape with head down aml, often, back feathers slightly ruffled. Then, with exaggerated fluffing of belly feathers, and sidewise movements that became faster and faster, then a wriggle, it pressed itself onto the eggs. In doing so it thrust its head far forward so that it rested aloug the ground. Hatching and care of nestlings. One egg pipped four days before it hatched (Table 2), but usually the first egg pipped 24-18 hours before the nest was empty. The young spent the first night in the nest if they hatched in the afternoon, but did not return once they left. Two birds (equally solicitous) accompanied the young from nest No. 4 into the marshes around Loon Pond on 17 July. But in four other cases we saw only one parent with a brood of four, as did Sutton (1932). When alarmed, the young ran very fast and even swam well, but they re- turned to shore at the first opportunity. At nest No. 3 two birds fluttered to within three feet of our faces in "frantic" distraction, 11 days before the eggs hatched. Reactions to intruders. The incubating bird was very tame; she sat until the intruder was within two or three meters. Once she had heen put off the nest, she ran around nervously and occasionally stopped and lmcked at the ground in a stiff, mechanical way unlike her deep probing when feeding. When with young, White-rumps, like Baird's, began to display when the intruder was as much as 75 meters away, but their concern did not reach the maximum shown at the nest until the intruder was at a similar distance (5 meters) from the young. The distraction display involved uo fluttering unless a young one was captured and held. We saw no wiug-up displays in distraction behavior. Feeding behavior. Unlike the Baird's Sandpiper, which fed by pick- ing from the surface in dry places, White-rumped Sandpipers fed by probing deeply in moss and wet vegetation. 'l?hey usually made two or three quick probes (from half to the full bill length), then ran sev- eral inches and repeated. 'l?he young fed in thick, soft, wet mosses, probing deeply like their parents. Dr. George W. Byers identified the stomach contents of two adults: 1. Three larvae of cranefly (Fam. Tipulidae, Gen. Tipula): 19 larvae of cranefly (Fam. Tipulidae, Subfam. Limoniinae); 3 spiders: 1 adult cranefly (Fam. Tipulidae, Gen. Tipula)--wing only. 2. One beetle larva (Fam. Carabidae); 41 cranefly larvae (Faro. Tipulidae, Subfaro. Limoniinae); nfiscellaneous fragments of I[IOSS. Presumably all of the larvae were secured by probing. B,4IRD'S SANDPIPER Calidris bairdii (Coues) (Eskimo: To6ee-to6ee or twee-twee) Reasons for including bairdii in Calidris are given below (Behavior and Systematics). The actions of this species are very similar to those of the Purple Sandpipers studied in Spitzbergen (Keith, 1938), and except for male incubation, to those of the Curlew Sandpipers studied by Portenko (1959). Habitat and density. The 28 territories of Baird's Sandpipers that we found in and around our study area were on barren, exposed ridges, terrace banks, and raised beaches covered sparsely with mat plants and large areas of bare soil (Figure 2--barren). They were the first places free of snow. They were clustered in a crescent-shaped area on the east- and south-facing slopes from just north of Iceberg Lake to the south end of West Ridge, rather than spread over the uplands. Steep slope or exposure to the prevailing east wind was correlated with dry- ness, barrenness, and early disappearance of the snow, all of wich attracted Baird's Sandpipers. We found only two territories at Ooya- rashukjooeet. The vegetation was considerably further advanced there than at camp, and there was a much smaller area of exposed sites suitable for Baird's. Territory. The displaying bird flew up from the ground in regular flight to a height of about 10 meters, then continued on xvith (1) a slow wingbeat; (2) wings set at a wide angle above its back; or (3) a quivering and shallow wingbeat (Figure 6). The slow beat or quiver- ing beat alternated with periods of sailing on set wings, and the bird ended the flight by coasting on set wings. Birds gave their flight song in any one of the three unusual types of flight, but most frequently while gliding. Before flying and after landing, the displaying bird usu- ally repeatedly gave long-drawn-out, slurred, hoarse toowee-to6ow.ee calls. The second syllable is higher and shorter than the first. We recorded flight songs as: (1) drrdrrrr zzxzzzzzzzzz; (2) increasingly rapid crescendo dreedree-dreedreedreedree trill, ending in dreedree- dreedreedree-dreedree. At the end of the song the wheezy twee-twee call came in threes now and then. It had a harsh quality in territorial disputes. As the displaying bird landed, it held one wing fully stretched straight over its head, and ran along the ground for about one meter (Figure 6). Occasionally it opened the other wing partly, but did not spread it, or spread both wings fully over its back. Sometimes it ran with one wing spread high over its back, then folded the wing, ran on, and spread and stretched the wing again. The raised and stretched wing was almost always the one toward the other bird. Sometimes the bird sang the trill on the ground, running or standing up very straight. The female at nest No. 3 crouched, stretched her head forward, and called coi-lt (Figure 6) when the male lighted from a song flight and ran xvith wings stretched above his calling drrrrrr. WING'UP DISPLAY ATTACK ALARM AT NEST DISTRACTION Figure 6. Baird's Sandpiper displays. An aggressive bird rushed at another with head dovn, bill thrust for,vard, and back feathers conspicuously ruffled. Most action on the ground consisted of running along ,vith head lowered. ,vings barely spread, tail spread and cocked up a little (Figure 6). When two dis- playing birds came together, they used the wing or wings-up display (Figure 6) and kept up a continual ,vhining cry, dree-dree or tii-ti or rarely drree-dree-dree. From 15-20 June, during the time of the most vigorous and continual displaying, eight to 10 Baird's Sandpipers fed together on the ,vet, sedgy, recently exposed cro,vns of the Bluffs ,vest of camp. As the sno,v left, these groups dissipated. Occasionally they sho,ved hostility, and sang, but ,ve sa,v no prolonged disputes. These birds ,vere pre- sumably nev arrivals that vere not yet territorial. We found neither nests nor parents in that area later. Keith reported (1938) that Purple Sandpipers had common feeding grounds. Other than this suggestion of one, ,vhich soon dissipated, ,ve found none. Baird's Sandpipers ,vere singing in the evening of 12 June and con- tinued to sing, especially in the evenings and mornings through egg laying; then singing decreased sharply as incubation started 23 June. We heard songs sporadically until 29 June and again for several days after 5 July, ,vhen the first young had hatched, both as part of display to an intruder and in the morning and evening, vhen ve were not intruding. The actions at that time vere the same as those during early territorial activities. Courtship. On 17 June, on a ,vet, bare, stony area on the edge of the sno,v, ,ve ,vatched a pair of Baird's Sandpipers in vigorous display for about 20 minutes. At first the male made several tvittering and trilling song flights along the edge and out over the snow, singing both ,vhile he fle,v and ,vhile he glided. He spread one ,ving high over his head, underside to,vard the female, immediately after he landed and repeatedly after,vard. Most of the time one bird crouched with head stretched to,vard the other, ,vhich stood erect and still. [le ruffled his back feathers and flev at the other, and the tvo fluttered up like game cocks, equally aggressively. After a flurry of fighting, both crouched, facing each other, vith heads dovn and forward. Next the male flev at the female and pounced on her back vhile she stood still. He stood on her back about 15 to 20 seconds, pulling out of her crovn some feathers that ve could see float avay in the vind. She stretched her head forvard and spread her tail vhile they copulated; occasionally she stretched one ving as if to keep balance. He got off, and stood stiffly vith breast and head raised vhile she stayed crouched. She lowered her head and started to run, at vhich he potraced, pecked at her head, and they copulated again. This happened three times; then she flew about 40 meters down the edge of the snow bank and he did not follow. Without 8X binoculars at 20 meters we would have thought this was a fight. Nest and eggs. Nearly all the nests were associated with a low hum- mock. The typical area consisted of coarse pebbles and black, dead mosses, over which vere scattered clumps of Gray Lichen, foliose and fruticose lichens (Cetrarias, especially cucullata [Bell.] Ach. and Par- reellax, Thamnolia v'ermicularis [Sw.] Ach., Alectoria nigricans [Ach.] Nyl., and A. ochroleuca [Ehrh.] Nyl.), tufts of Grass Rush, Arctic Bluegrass (Poa rigens Hartm.), Poppies, Purple Saxifrage, Bell Heather, and Arctic Willow. Sites were often marked with frost cracks, where mosses, sedges, and mat plants (Avens, Bell Heather, and Arctic Willow-) were more conspicuous in the low places. The earliest nests--Nos. 1, 5, 6, and l 1--were placed on especially wind- blown and south-facing areas. We concluded that nests Nos. 2 and 6 were displaced by our making camp on the beaches where the Baird's Sandpipers were trilling on 13 June; but incubation must have started in nest No. 6 the clay after we arrived (hatched 3 July). On 19 June, the first day of incubation, we watched the bird on nest No. 2 (Table 3) while it sat and added to the nest. It reached out to the front and sides, picked up sprigs of moss, Grass Rush, or Bell Heather and, sweeping its head down and backward as if brushing its breast feathers, carried the sprig back to the fold of the wing or all the way back to the base of the tail and beyond to drop it. Birds at nests No. 2 and 3 (before the clutch was complete) spent as much as half an hour on the nest--"building," frequently leaving and returning. The bird at nest No. 3 used Arctic Willow leaves. At nest No. 3 and nest No. 2, an egg was laid every other day. The earliest egg in our study area was probably laid 6 June (nest No. 6). The last egg in our study area, in nest No. 14, was laid on 28 June. Clutch size in all nests was four. For data on nests see Table 3. Activities during incubation. At 10 nests we found a bird incubating at nearly every visit, but at tvo we found the parent missing relatively frequently. Several times during incubation we saw both parents at a nest; and we noticed a marked day-to-day difference in the aggressive- ness of the incubating birds (see below--Reactions to Intruders). The less-solicitous parent was at the nest on approximately 20 per cent of our daytime nest-checking rounds at the 10 nests mentioned. The more-solicitous parent taken with young on 21 July was a male. When the bird ran in and settled on the nest, it usually first put its bill down among the eggs (not seeming to arrange them), and then vigorously 'I'A BIE 3 Nsq ß D^T.,--BAIRD'S SANDPIPER Date found and contents First egg No. of young Nest No. on that date hatched produced 1 16 June (4 eggs) 7 July 4 2 18 June (3 eggs) 10 July 4 3 17 June (2 eggs)  -- - 4 22 June (4 eggs) 11 July 4 (no egg left) 5 26 June (4 eggs) 7 July 4 " 6 26 June (4 eggs) 3 July 3 " 7 28 June (4 eggs) 13 or 14 July ? " 8 30 June (4 eggs) 8 July 3 9 3 July (4 eggs) 12 July 4 " 10 3 July (4 eggs) (not revisited) 11 5 July (4 young) 4 or 5 July 4 12 5 July (4 eggs) 19 July 3 ( 1 did not hatch left in scrape) Clutch size four in all 12 nests. Nest No. 3 destroyed by a dog. shuffled from side to side and squirmed more and more rapidly down onto the eggs. It held its head in on its shoulders and did not thrust its head as far down and forward as did the White-rump. Incubation period at nest No. 2 (found before completion of the clutch) was 21 days. Tis seems to have been unrecorded previously. Hatching and care of nestlingsß Eggs hatched between 3 and 19 July, but the eggs of seven nests hatched between 7 and 13 July. All but one egg pipped the day before hatching; that egg pipped two days before hatching. In several nests one, two, or three eggs hatched in one day; and in every case the young left the nest the following day. We have no indication that the young returned to the nest after the last egg' hatched. After hatching, the young often stayed several days in the vicinity of the nest, accompanied by both parents, and then moved to wind-blown, well-drained soils of frost-patterned areas and old beaches, or to muddy pond shores thinly scattered with sedges. The parents leading young gave a new alarm call--drrrreeee or drrrreeeet-- not so low as the call note on migration, nor so mellow as the tzii-ttii. The yotmg were slow and clumsy for three days after hatchingß Either parent's song or the drrreee alarm made the young "freeze" the first day and for at least two weeks after hatchingß We saw no pooling of young into flocks, but when young were disturbed, parents from nearby broods showed alarm and sometimes joined in distraction. Reaction to intruders. Until the clutch was complete, parents showed little concern at the nest. With the start of incubation, the parents became solicitous, sat very close and, xvhen disturbed, fluttered at an intruder and performed distraction displays. The birds were markedly more solicitous in cold weather than in warm. The parents were secretive and seemed anxious to get the intruder away and then get back to the nest. Some birds returned to the nest if we sat down, as close as two to three meters. When we left they followed some 40 meters, calling; then, with head down and feathers smoothed, they ran back to the nest, stopping two or three times to look and call. In comparison with White-rmnped Sandpipers, Baird's left the nest more readily, which made Baird's nests much easier to find. Rarely, calls of ti-ti at the nest attracted a second hird, which stood iu the background, calling occasionally. We saw no aggressive behavior toward the second bird. One parent at nest No. 4 left before we were 75 meters away, and did not return until we were 50 meters or more away. The other parent let the observer get within 20 meters without an outcry; then flew at him. In contrast, both parents at nests Nos. 6 and 7 were much wilder. When the eggs were pipping and hatching, and when parents were escorting young, aggressiveness and distance at which they started at- tention getting (advertising display) increased markedly (to as much as 300 meters), and several neighbors entered the territory of a bird that was displaying. The adults made themselves conspicuous as if to keep the eyes of the intruder up and away from the young. Wben we got in among the young and they broke out of hitling, the parents quickly flew toward us and started creeping over the ground, flapping both wings, and crying pew, pew. There was a call that made the young break out of hiding and run to the parents, but [ do not distinguish it in my notes. On 5 and 21 July parents sang in the air before perform- ing vigorous distraction display, and again when we had moved off about 60 meters. Feeding behavior. The dry surfaces of Baird's habitat were shitable for their technique of picking food off the surface. The stomach contents of three adults were identified for us by I)r. George W. Byers: Fragments of two beetles of same species (Faro. Carabidae); one spider; one snmll crustacean (leg only); one beetle larva (Faro. Carabidae); and miscellaneous plant fragments, including nloss leaves and steins. One fungus gnat (Faro. Mycetophilidae--wing only); three beetles of two species (both Faro. Carabidae); one adult cranefly, male (Faro. T'ipulidae, Gen. Tipula). TABLE 4 UMMARY COMPARISON oF THE SANDPIPERS .Auk Vo,L 78 14/hite-rumped Sandpiper (Heteropygia) Baird's Sandpiper ( Calidris ) Nesting Site Well-vegetated sites among clumps in carpet of vegetation, in a moss base. Nest in clump of vegetation, on moss and plant foundation. Wind-blown, lichen-strewn, early snow- free areas, with many bare patches. Nest on bare soil; scrape made in natural depression. Excitement Raises head and sleeks plumage before flight display. Raises head and sleeks plumage before flight display. Aggression (a) Head thrust forward, back feath- ers ruffled, wings spread to sides, tail slightly cocked; crouching run. (b) At the end of "Sharp-tailed dance," head is raised and near wing often stretched over the head. (a) Head thrust forward, back feath- ers ruffled, wings spread at the sides, tail partly fanned; crouching rut1. (b) Runs in front with head raised and near wiug stretched over back showing under wing. Appeasement Stands with head raised. Stands with head raised. Action of Companion during Display During "Sharp-tailed dance," several times raised head and then near ving. At end of song flight, crouched, thrust head forward and called co-it. Both actions similar in ground displays. Alarm Call---Advertisement None heard. Todwec-to6,wec. Courtship Display Ground display Varied and ritualized. (a) Rutis to companion in aggressive posture or (b) Performs dance with wings stiffly spread, tail cocked straight up and furled, head thrust forward, calling bzzzzzip. (c) Stands before coml)anion vith tilted tail and raised vings. Similar to aggression. (a) Runs to companion in aggressive posture or (b) At end of flight display, stops and stretches near wing up, occasion- ally calls to6wee-to6wee or trills as in flight song. TABLE 4 (Continued) White-rumped Sandpiper (Heteropygia) Baird's Sandpiper (Calidris) Dispray flight Flies up to about 15-25 meters where hovers or sails, calling: (a) Trill like a fish reel, sometimes ends with zip-zip call as floats down. (b) Call of ng-oik, bobbing head, then sails down on set wings. Display flight occasionally given with two or three birds in the air, seemingly both male and female; one did not posture in flight. Flight sweeping over large area. Flies up to about 15 meters where hovers or sails, calling a ral)idly re- peated alarm or trill. Display flight only seen to be given by a single bird. Flight localized over small territory. Flight song Clearly differentiated from ground song, and of two types: "small pig" and "fish reel." Decreased with start of incubation; last heard 30 June. Given on tbe ground and in air: todwee-to6wee, rapidly repeated; grades into trill. Decreased sharply with start of incubation; reappeared after young hatched. Distraction Display dggrcssion (a) Flight songs of both types given at start of incubation period. (b) Stands with head raised, feathers sleeked and silent; runs rapidly, crouching, head thrust down and forward, back feathers ruffled, wings usually barely spread, tail fanned and tilted, squeaking and twittering constantly, occasionally crouching in a depression. (c) Flutters into intruder's face, squeaking and twittering, Sat close using conceahnent. (a) Flight song at start and end of incubation period. (b) Stands with head raised, feathers sleeked, calling todwee-todwee: runs rapidly with head thrust for- ward, back feathers ruffled, wings partly to almost fully spread (more widely spread than by White- rump), and head held out stiffly, tail fanned and tilted; stops to cry to6wee-todwee, or twitters (low grating peeew-peec.w) while running. Comes closer (2-4 meters) when behind observer. (c) Flutters at intruder's face, and when alighting stretches one wing high over back, and may present one wing, in a posture similar to the one-wing display. Showed aggressive actions at greater distance, presumably as demonstration display. TABLE 4 (Continued) I47hite-rumped Sandpiper (Heteropygia) Runs along in crouch, about 4 meters from intruder, wings held at the sides or tips across rump, partly open; tail fanned and tilted down, head thrust forward, squeaking; zigzags and starts and stops. If ignored, (b) and (c) above. Displacement feeding. Occa- sionally crouched briefly in hollow with head forward as if onto eggs. Leads about 10 meters from nest, then runs around to the side, back to the nest, with short nervous runs. Leading away is a clearly expressed action. Baird's Sandpiper ( C alidris ) Leading away Runs in crouch, at an angle to in- truder, wings partly open and lowered, the near wing dragged, tail occasion- ally fanned and tilted, head thrust for- ward; stops and raises head to cry towee-to6wee, starts and stops. Leads about 10 meters from nest. Leading away is much less well developed. At Nest Clutches completed 25 June-2 July. Only one sex seems to incubate; in at least one case, both parents accom- panied young; in four others, only one parent was seen with young. Concern at the nest increased just before and after young hatched. Clutches completed 12-28 June. Both sexes seem to incubate and show con- cern; both sexes accompany young. Concern at the nest greatly increased just before and after young hatched. Feeding Feeds by deep probing; stomach con- FeetIs on the surface; stomach con- tents were larvae. tents were adult and flying insects. Territories Six nests in one square mile of our Twenty-five territories in one square study area; arrived after the snow had mile of our study area; were on terri- left the lowlands--19 June. Territo- tory when we arrived. Territories ries large and complex; two nests 35 averaged 50 meters across, simply or- meters apart suggests polygamy. ganized. Young Hatched 15-22 July. Strongly buffy Hatched 3-19 July. Grayish-white below. below. Eggs Greenish-brown background color with Tan to chocolate-brown background darker spots and splotches. Females color with darker spots and splotches. I and 4 laid two days after arrival. Incubation period 21 days. Calls Mouselike squeak. "Fish reel." "Small Dreeet or to6wee-to&vee. Trill. pig" ng-oik. 3. Two beetles of same species (Fain. Carabidae); two muscoid flies (probably Fam. Antholnyiidae); one adult cranefly, male (Fam. Tipulidae, Subram. Limolfiinae, Limnophila sp.); many cranefly eggs and leg segments (Fam. T'ipulidae, Gen. Tipula); and many segments of legs from a sleuder-legged arthrot)od, per- haps a phalangid. All of these animals could have been picked from the surface. Migrants. Nonbreeding birds gave the ti-t,i calls, but we heard the hoarse drrrreeeet of birds on migration first on 30 June. We sav the first flock 7 July; five on 11 July; then 16, seven, and five on the walk to Oonakuktooyuk on 20 July. SANDERLING Calidris alba (Pallas) (Eskimo: [dlouk and his family had no name for this species) The reasons for including alba in Calidris are given below (Behavior and Systematics). We saw one bird in distraction display on the dry uplands near Oonakuktooyuk. It ran with head low and neck thrust forward, calling drreeet or tweeet, tweeet, bobbing occasionally like a Spotted Sandpiper. Then it flew, alternating periods of ordinary flight with periods of rapid, shallow wingbeats, again like a Spotted Sandpiper. The vegetation of the site was like that described for the nesting of tlfis species in Greenland (Salomonsen, 1950-1951), streaked with alter- hate lines of vegetation (lnosses, Averts, Arctic Willow, and some sedges) and ahnost barren soil, so regular as to seem ploughed. II. BEHAVIOR AND SYSTEMATICS Heinroth (1911), Lorenz (e.g., 1941), and Mayr (1942 and 1958) have emphasized the importance of behavior in systematics. In this paper an attemi)t is made to use behavior to help define genera of plovers and sandpipers. Our observations indicate that the courtship displays of the plovers (Ringed, Golden, and Black-bellied) contained similar elements, while the displays of the sandt)ipers were varied. The actions of the Baird's Sandpiper were simple and generalized. The similarity of actions (rushing, displaying of wings, and fluttering) that preceded copulation, to those seen in aggressive situations and in the presence of a hmnan Jutruder, suggests that ritualization has not advanced very far, either to rigidity of the iudividual actions or to separation into several dif- ferent actious. However, the soug fii2'ht and dance of the White- rumped Sandpiper do not grade into any of its other activities, and thus are more "derived" or "less probable," as Lorenz (1935) says. On this purely behavioral basis, the sandpipers are less closely related thau the plovers. Yet nearly all students place the White-rumped and Baird's sandpipers in the same genus, while putting each of the three plovers in a separate genus. This may only show the danger of making comparisons between subfamilies, based on oue taxonomic character (behavior in this case). Plovers. Displays, nesting sites, eggs, nestling aud adult plumages, and skeletal features show that Golden Plover and Black-bellied Plover (Table 1) are very closely related and, in fact, do not justify separate generic status (Van Tyne and Drury, 1955 and 1959). Although we found the behavior of these two species similar, many behavior charac- teristics are uniform for all the plovers, and to use these as the only basis of classification would produce results as unsatisfactory as has the use of only morphological features. Lowe (1922) pointed out a morphological separation: presence of rudimentary hind toe and two cervicodorsal vertebrae with free ribs in the Black-bellied Plover, in contrast to lack of rudimentary hind toe and presence of three cervico- dorsal vertebrae with free ribs in the Golden Plover. Lowe also listed nestling plumage and features of the osteology of the skull. We found the presence of the white collar--uninterrupted in the Black-bellied Plover and interrupted in the Golden Plover--but this is not vithout exception (see photograph in Van Tyne and Drury, 1959). The differences in the skull, described by Lowe as conspicuous, are dictated by the habitats of the two species, as Ernst Mayr suggested to me in 1954: the Black-bellied Plover is marine and the Golden Plover largely fresh water in the nonbreeding season. Nasal glands, corre- lated with the marine habitat, have by their size and pressure suppressed the formation of bones and modified the region at the base of the bill, complicating embryological processes and degree of ossification in the Black-bellied Plover. Bock (1958) discusses this problem in detail, especially the structure of the skulls, and reviews the confused history of the classification of plovers based on (1) functional characters (plum- age color and skulls), and (2) the presence or absence of a hind toe. The last character comes and goes without relation to other taxonomic features. Mayr (1945) aud Delacour (1951) show the superficiality of the hind toe as a generic character, both in plovers and in sandpipers. Fftnge, Schmidt-Nielsen, and Osaki (1958) and Schmidt-Nielsen (1959) show that the nasal glands have a salt-excreting function in species that drink salt xvater. This explains the taxonomic distribution of these glands according to species habitat and why they are so inpor- tant that skull modifications appear to accommodate them. Features directly selected by habitat are not of generic value. The ground displays, especially of aggression (Table 1), appear in- distinguishable between Golden and Black-bellied plovers, but differ in detail from those of the Charadrius plovers that I have seen in Killdeer, Semipalmated Plover, and Piping Plover (Charadrius melodus) and that Edwards et al. (1947), Laven (1940), and Mason (1947) have described for Ringed Plover; Ledlie and Pedler (1938), Dathe (1953), and Simmons (1953) for the Little Ringed Plover; and Simmons (1953) for the Kentish Plover (Uharadrius alexandrinus): e.., (1) the raising of wings (correlated with colored axillars) in aggressive situations appears in the Pluvialis plovers, not in Uharadrius; (2) the ruffling of back feathers and lowering of head (correlated with brightly patterned back) in aggressive situations is emphasized by Pluvialis plovers, while Uharadrius plovers emphasize the throat and breast (cor- related with contrasting dark and white rings) and the fanned tail. Furthermore, (3) head-bobbing displacement activity (raising head, neck, and forward end of the body while lowering the tail) is absent in Pluvialis plovers, and universally present in Uharadrius plovers. In distraction display, the two ?luriaIls species seem to differ, but actually the differences are in degree only. Golden Plovers stood up and faced the intruder and approached directly. When running away, Golden Plovers did not crouch as low as the Black-bellied, nor did they throw themselves into a depression. Their more upright posture in rnnning and beating wings created the illusion of a four-looted animal --"the rodent run." Black-bellied Plovers spread their wings more fully, thrust their heads down and forward, and crouched lower; they approached the intruder diagonally and stood at an angle. Both male and female Golden Plovers distracted, whereas only male Black-bellied Plovers did. Actually the distraction by the female Black-bellied Plover at nest No. 4 xvas similar to that of the Golden Plover. It will be important for comparison to have more details of the distraction dis- plays of female Black-bellied Plovers and male Golden Plovers from other areas in order to see whether there is geographical variation and to see xvhether the differences that we observed are species specific or sexual. In these displays, both of the Pluvialis plovers use their wings in unison. In contrast, the distraction display of Charadrius plovers (e.cj.. Ringed Plover, Little Ringed Plover, Kentish Plover [described by: Armstrong (1952), Dathe (1953), Edwards et at. (1947), England et al. (1944), Ledlie and Pedler (1938), Mitchell (1935), Simmons (1952, 1955), Sutton and Parmelee (1955), and Williamson (1947)1, Killdeer and Piping Plover) are alike in those features that differ from the display of the Pluvialis plovers: e.g., wriggling along the ground, leaning on one side and waving one or both wings in an uncoordinated way (broken wing act)--see illustrations of Killdeer (Deane, 1944) and Little Ringed Plover (Dathe, 1953; Simmons, 1955). In the Charadrius group, one wing seems to wave independently of the other. Ringed Plovers, Little Ringed Plovers, and Killdeer may turn on an intruder and approach with wings raised and spread (see illustrations in Simmons, 1955, which also show a Kentish Plover sprawled in a posture very like that of a Black-bellied Plover). The tail is fanned and quivered in Charadrius, and I have not seen the tail cocked up in this context. Both Black-bellied and Golden plovers may tilt and cock their tails when bowing before an intruder. We never saw hiaticuIa run xvith head lowered and back feathers ruffled as in Black-bellied and Golden plovers. They ran either with heads pulled in onto their shoul- ders (crouch run, Simmons, 1955) or with head raised and body feathers sleeked, as Golden Plovers did or Black-1)ellied Plovers (lid when "ridden off" by Goldens. When Charadrius plovers crouch, they seem to try to hide; when Pluvialis plovers crouch, they "pretend" to settle on a nest. Sandpipers. Te relationships within the sandpipers are more com- plex. Skins show that the young of Baird's and White-rumped sand- pipers are similar to the other species of "EroIia," to which the young of CaIidris (Ereunetes) pusilla are also very similar. This led Van Tyne to agree with Witherby et aI. (1940) that pusilla be included in the same genus with bairdii, alpina, and minutilla. T]e behavior of these species, as described by various authors, agrees. Many fragmental and some fairly complete descriptions are available--e.g., quotations in translations of Birula and Suschkin in Pleske (1928), Brandt (1943), Brown (1938), Haviland (1915 and 1916), Keith (1938), Portenko (1959), and Sutton (1932). In aerial song, aggressive action, and distraction behavior, Knot (Calidris canutus), Sanderling ("Crocethia" alba), Dunlin (alina), Purple Sandpiper (maritima), Semipalmated Sandpiper (pusilia), Western Sandpiper (mauri), Least Sandpiper (minutilIa), Temminck's Stint (temmincki[), and Curlew Sandpiper (ferruginea) are similar in noncomplex actions, little ritualized from hostility postures. Their trilling song is given while hovering or in butterflylike flight. T'he song grades into a characteristic scold note. In fact, behavior indicates that Knot and Sanderling (both using wing-up threat action--Birula in Pleske, 1928) are closer to most of the members of Calidris than are fuscicoIlis and melanotos. The Knot's song departs from the usual trill to a call kou-hi, not unlike a Baird's to6oowee. According to Sutton (1932) fuscicollis resembles melanotos in the presence of throat or pectoral sacs. The reproductive behavior of these two: flight song, "sharp-tailed grouse" display and failure of the male to take part in incubation suggest that melanotos and fuscicollis are at a different level of ritualization from that of the rest. The male Curlew Sandpiper, otherwise closely resembling the other Ualidris, is reported by Haviland (1915) and Portenko (1959) to take no part in incubation. The spring plumage changes in Knot, Curlew Sandpiper, Sanderling, aud Dunlin form a series with the Least and Semipalmated Sandpiper and Stint type of spring plumage. The feeding habits do not clarify the classification. The two major techniques: (1) quivering, probing action characteristic of fuscicollis and (2) a stabbing peck--bairdii--cut across the taxonomic features. Earlier authors (Hartert, 1912-1921, and Witherby et al., 1940) in- cluded all these species iu Ualidris (excluding alba). Mayr (Delacour and Mayr, 1945) included alba in Ualidris, and I agree. The place of the Stilt Sandpiper (Micropalama himantopus) needs clarification by behavior study. If any species are taken out of the genus Calidris, fuscicollis and meIanotos should be the first. Pitelka suggests relationship of these to the Ruff (Philomchus pu(.qna.v). The members of Calidris (s.l.) are sufficiently different from melanotos to justify its separation even as a monotypic genus. Now the questions arise whether fuscicollis (1) lies outside the extremes of variation represented by the other Calidris (s.l.); (2) is different enough to justify a monotypic genus: (3) is close enough to melanotos to justify inclusion with it; (4) is closer to the other peep that have a white rump and decurved bill (ferruginea males do not incubate; even himantopus shows sexual size differences that are suggestive). Present knowledge suggests that fuxcicollix be- havior is beyond the limits of variation known within the rest of Calidris (s.I.) and has moved in the direction of melanotos although not as far. Because of this, I suggest reinstating Coues' ( 1861 ) gelms Heteropygi. of which fuscicollis is the type and about which there is no nomenclatural doubt. Portenko (1959) retains Heteropygia for melanotus. Species included in this genus by Sharpe (1899) are mdanotos ("macu- lata"), fuscicollis ("Bonapartei"), and acum. inata; and, in addition, bairdii. My studies exchlde bairdii from the genus Heteropygia. as here, and show its relation to Ualidris. III. ECOLOC, mAL INTERACTIONS OF CLOSELY RELATED SPECIES What mechanisms in these six shorebirds allow sympatry without interbreeding or ecoloo*ical interference (competition) ? Darwin (1859) established that closely related species tend to compete for habitat and food necessities. Recently several studies (Gibb, 1954; Hartley, 1953; MacArthur, 1958) have examined the segregation of habitat or food that prevents direct competition between closely related species. Shore- birds are especially favorable subjects for this type of study. On migration they might be able to take advantage of what Lack (1954) calls a superabundant food supply, but actually we can assume that they do not because of observably different feeding techniques. Our studies of shorebirds on Bylot Island show that these species are subject to the classic rules of ecological competition and segregation. Interaction of plovers. We found habitat segregation betveen Golden and Black-bellied plovers, but the segregation vas not clear nor did it seem effective, because ve also found conflict betveen the tvo. Arm- strong (1952) described conflict between Little Ringed and Ringed plovers vhere these tvo largely allopatric species overlap as a result of recent changes in range. Tle tvo Pluvialis plovers survive sympatri- cally here, but over most of North America their breeding ranges do not overlap. Because ve should expect that there vill be geographic variation in the mechanisms alloving sympatry, it vill be interesting to study interspecific relationships in other parts of their overlap, e.9., Alaska and Siberia. Dementiev et al. (1951) state that in the Soviet Union the Enropean Golden Plover nests in the marshy and vetter parts of the tundra, vhile the Black-bellied Plover avoids these and selects the higher, dry tundra. Gladkov (in Dementiev et al., 1951) says that squatarola and apricaria mutually exclude each other, but the authors comment only that dominica is more numerous on the Taimyr Peninsula vhere it shares the dry biotope vith squatarola. Black-bellied Plovers began to lay later than Golden Plovers, vhen most of the uplands vere free of snov, yet chose restricted areas--the most barren. They fed on dry places in contrast to the vet, often marshy places vhere Golden Plovers fed. The late arrival and laying, and exposed habitat, allovs Black-bellied Plovers to be High Arctic breeders. In contrast, the calendar and the vegetation of their habitat suits Golden Plovers to the Lov Arctic. Where Golden and Black-bellied plovers occur together, displacement (character displacement of Brown and Wilson, 1956) can be expected to exaggerate the site-preference differences. This habitat displacement must depend on the local nature of the vegetation and must be a re- versible process, depending upon ability of one species to appropriate nesting sites of its choice. Conflict between Golden Plover and Black-bellied Plover. On 8 and 9 July, at Golden Plover nest No. 2, a male Black-bellied Plover, vhich persisted in approaching too close, was repeatedly attacked and driven off. Whenever the Black-bellied approached, one or both Goldens ran at him (Figure 3), calling pzvit-pwit-pwit, sometimes attacking in a flying dive, and the Black-bellied Plover, retreating, flew up, wheeled, and dove at one of the Goldens. The Golden stood its ground but crouched, spreading one wing momentarily (Figure 3), as the Black- bellied passed over and settled. Occasionally one of the Goldens cried ka-sweeooow'it, bobbing its head violently. Tle Black-bellied Plover held its neck stretched up (appeasement) and occasionally called kleeeee. The Golden Plovers did all the aggressive displaying. When we approached, the female Golden ran up to us with head partly lowered, breast feathers fluffed out, and scolded pwit-pwit-pwit. On 12 and 14 July we watched Golden Plovers pursuing female Black-bellied Plovers in three different places on the uplands and at the mouth of the river at Ooyarashukjooeet (Figure 3). Pursuits, scarcely 20 meters at Aktineq, were 100 meters to half a mile at Ooyara- shukjooeet. Our notes indicate that most trespassers were females. The conflicts increased toward the end of the incubation period, perhaps because the longer time gave the Black-bellied Plovers more opportunities to find nests. Unsatisfied incubation drives may be the behavioral basis of the trespassing because both species should respond to the similar eggs of the other. I would expect the incubation drive of a bird to decrease as the incubation period passed, if she were not incubating eggs to rein- force the drive. Our few observations do not allow us to say whether there were interspecies territorial struggles or not. But Golden Plovers laid eggs about two weeks before the Black-bellied Plovers in "neighboring" territories, and the periods during which territorial aggression is evident must differ. These conflicts expose the eggs of Golden Plover to greater danger from cold and predators, but we found no lessened nesting success. The species that harries another while incubating its own eggs can be expected to hold the breeding ground. It will be interesting to see the expression that the competition takes farther south, where Golden Plovers replace Black-bellied Plovers. The third plover (Ringed Plover) occupied the especially barren or vegetation-free habitat of active sea beaches and abandoned river bars. Differences of habitat, size, and displays (voice and patterns of plum- age) separated this population so that there was no problem of overlap or competition. Interaction of sandpipers. The three species of sandpipers ignored each other. Baird's Sandpipers arrived, probably by 1 June, and occu- pied the most barren places to nest and feed on surface-living insects. White-rumped Sandpipers arrived on 19 June and occupied vegetated, relatively sheltered areas. They fed by probing deeply into the moss. We found Sanderlings on dry, frost-lined uplands where we saw neither of the other species. Baird's is adapted to High Arctic breeding grounds, while the White-rump is adapted to the mossy bogs of the Low Arctic. I have no data on the feeding of the High Arctic Sander- ling on its breeding grounds, but on migration it probes shallowly and frequently uses a turnstonelike technique in seaweed. In the two plovers and the two sandpipers that we studied in detail, territorial boundaries were universally ignored by the time the young had hatched and left the nests. Parents and their young readily crossed territories and gathered in favored feeding places. This argues against ay direct food function of territory unless in the realm of a "non- proximate" influence of preventing aggregation of breeding pairs be- yond a "certain concentration." This concentration will be very hard to establish, because territories are highly compressible, especially under conditions that lead to crowding, e.g., a late spring. Such conditions do not vary with the food supply at the time when the young have hatched and are learning to find food--one of the critical times of food pressure. IV. ETHOLOGY oF DISTRACTION DISPLAYS Although I recognize the fundamental value of the scheme of "con- flict of drives" proposed by Hinde and Tinbergen (1951), I think that to classify all displays as the result of the relative strengths of the conflicting drives is to oversimplify. Is it not possible that many displays have been selected for themselves and their present function, without concern for their basic motivation? Is it not possible, too, that the original motivation may itself have become lost, transferred, or ritualized? Furthermore, if the immediate motivational context exists, as that theory suggests, why is there the great difference in specificity between distraction and courtship displays ? Distraction displays are selected to function as a whole. I endorse Simmons' (1955) abandonment of his earlier classification, which sepa- rated "static" and "mobile" lures, because such classifications (see also Armstrong, 1949) suggest uniformity in xvhat is actually a spectrum of intensity, as Simmons pointed out. He also pointed out that the nse of the word "displacement" activity, as it applies to aggressive and brood- ing drives, is misleading in distraction displays, and he enphasized the importance of the aggressive notivation. The explanation of distraction displays, on the basis of a conflict situation, suggests a basis for the gradation and variation seen during a series of encounters; but I agree with Simnons that distraction displays are not expressions of drives thwarted at present, and are clearly ritualized into a specific action of survival value. It is also obvious (Skutch, 1955) that there cannot be impairment of coordina- tion. In the conflicts betxveen Golden and Black-bellied plovers, all distraction displays were absent--even nest-defense postures. Deane (1944) reported a marked difference in distraction displays of Killdeer, when directed to cow or horse, or to man--yet the same conflicts of drives were present. Clearly, then, these postures are not an expression only of conflict of attack and flee drives, but are separately ritualized. At present, although there is gradation in the intensity of display, each stage in the gradation is uniform. If present conflicts of drives were responsible for impeded actions, one would expect different forms and conbinations of actions from each individual at each visit. Instead, the whole distraction action is ritualized and selected as a unit. Plovers. Males of both Black-bellied and Golden plovers showed aggression to the intruder (head loxvered and back feathers ruffled) and occasionally came very close in a conspicuously aggressive posture. The aggressive rush was more evident in Black-bellied than in Golden action, perhaps because the male did nost of the distraction. The butterflylike display flight in distraction of Ringed Plovers nust be largely motivated by hostility, as it is in its intraspecies context. This grades into a demonstration display, which is even more conspicuous in other species: Baird's Sandpiper and Lesser Yellowlegs (Totanus flavipes)--(in my experience); godwits (Limosa); Redshank (7'0- tanus totanus)--( Simmons, 1955). The gradation of each action into most of the others must be empha- sized. As the drives of aggression, flight, brooding, fear, and conceal- ment rise and fall, the bird approaches and threatens, settles into a hol- low, flattens itself on the ground, and spreads its wings--yet stamps its feet and beats its wings. Any movenent stimulates fleeing, and the bird runs off, flopping or shuffling. The aggressive actions, the stand- ing and calling ("static lure"), and the flight over the ground ('Snobile lure" or "rodent run"), all serve, in present practice, functions different from their "original" conflict of motives. They now serve to attract attention and lead the intruder off. As such, the actions are ritualized, but this does not mean that the basic "tendencies" are totally removed. It has 13een generally accepted that a movement can become ritualized --thus stereotyped, modified, and removed from its original context. ls it not possible that a posture can become ritualized and removed from its original motivational context, too? Meyerriecks (1959) documents the emancipation from the attack-flee-sex motivational conflict of crest raising in Green Heron (Butorides virescens). I suggest that distrac- tion displays must be considered separate from their original motivations and that the whole act has become ritualized, including its motivation. The concept of conflict of drives is an excellent ground work for under- standing, but it is dangerous to explain all postures, and especially the highly ritualized ones, on the basis of their elements of hostility, sex, and fleeing. An action such as distraction display may itself become a unified "uneasiness action" or "displacement activity." Once this has happened, interpretation of the elements of the posture according to the meaning of the components in an "original" conflict situation will pro- duce either nonsense or an unnecessarily complex "dissection." Tle action is an element in itself, no longer compound. In this context, the elements of attack, flee, and sex exist as motivations--but also, so do distraction, nest defense, alarm, response to predator, and probably many others. 3andpipers. The sandpiper species varied in the amount of calling during distraction, and in aggressiveness. It may not be coincidence that Baird's dancing, wing-quivering distraction was not present in the White-rump. In White-rumped Sandpipers, a similar act is part of the courtship ceremony! The brooding or nest-defense posture, conspicu- ous in the plovers' actions, was not conspicuous in those of the sand- pipers. The brooding drive was stronger in sandpipers than in plovers, hovever, because the parent sat closer. The difference may be associ- ated with difference in size and color. Comparison distraction and courtship dspIays. Why are similar distraction displays so widespread and courtship actions so specific? The similar series of actions in the distraction of plovers and sandpipers may be "old actions" or the result of convergence in the tundra habitat, but they do not occur in the other families we observed. In contrast, the well-known tameness of tundra species is probably convergence, because of the distances a parent can be seen once it leaves the nest. This visibility requires that parents abandon early or sit tight. The uniformity of distraction display in the plovers and sandpipers, even to the point of retaining the broad intergradations of action, is shown by the uniformity of actions at different nest sites, and it con- trasts with the differences in courtship and hostility displays. This is to be expected from the "purpose" of these actions. Distraction has a shotgun effect, and the selective action of species-specific differentiation serves no purpose. In contrast, in courtship, selective advantage, where species overlap, has ritualized certain actions and emphasized differences that provide the species with isolating mechanisms (Brown and Wilson, 1956). In the courtship displays there is uniformity in detail, pre- sumably because of the one male to one female relation in pair forma- tion, in contrast to the one to "anyone" in distraction. Both types of ceremony are uniform, but in the one, each specific act is important; and in the other, only the whole effect is important, and it must be generalized enough to attract attention of several kinds of preclators. Because of this ritualization, the original motivations are not clear in distraction, and only comparative studies can clarify them. 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