1. TRIBE TADORNINI. SHELDRAKES The sheldrakes, a name under which we include the related genera Chlophaga, Cyanochen, Neochen, Alopochen, "Casarca," and Tadorna, form a group of ducks which are not far from the river ducks. The resemblance to the geese, which has led to names like Egyptian Goose, Orinoco Goose, and Blue-winged Goose, is entirely superficial. The South American Crested Duck (Lophonetta) is related to the shel- drakes, as are probably also the primitive Australian Cape Barren Goose (Cereopsis) and the South American steamer ducks (Tachyeres). Members of this tribe are characterized as follows: bill compara- tively short and thick; legs long; neck short; coloration in the two March 1945 12 THE WILSON BULLETIN vol. s7, o. 1 sexes either alike or different, but bright in both; voices of male and female very different; a spur-like bony knob on the bend of the wing (metacarpal joint); a bold color pattern of the downy young (black and white or grayish-brown and white); a white nest-down in many species; wings adorned (except in Cereopsis) with a broad metallic speculum, which is formed by the secondaries or greater wing coverts; lesser and median wing coverts of a uniform snowy white (except in Cereopsis and Cyanochen, where they are light grayish-blue, in Neochen, where they are purplish-black, and in Lophonetta specu- larioides, where they are gray). Sheldrakes are very quarrelsome; each pair keeps apart from other individuals of the species. Females indulge in special "incitement displays" which are im- portant in pair formation. In the Ruddy Sheldrake (Tadorna ["Casarca"] ferruginea) in which this display is particularly well de- veloped, it has been described as follows: "On approach of intruder female makes kind of feigned attack, with neck extended and head close to ground, constantly uttering anger-note, and if it does not withdraw she returns to male, running frantically round him .... till he attacks the stranger and if possible drives it off. Male appears to have no courtship, but female takes initiative in attaching herself to a male and inciting him to attack others .... Females not yet definitely paired may incite different males against one another, apparently preferring strongest and most bellicose" (Witherby et al., 1939:228, after Heinroth). These agitation displays occur in rudi- mentary form also in the mallard and other river ducks. The eggs are smooth, not rough as in the geese, and only the females incubate. The males, however, guard the nest from a dis- tance. The Tadornini apparently pair for life, but accurate obser- vations on this point are not available. Members of the genus Tadorna nest usually in holes in the ground except T. radjah, which nests in tree holes. Accurate records of the nesting habits of Cyanochen or of Lophonetta in the wild are lacking. Chlophaga and Cereopsis nest on the ground. Sexual maturity and the pugnacity connected with it are usually reached at the age of two years. Adults of the tribe dive only when wounded and before coltion (Tadorna). The pre-copulatory display of T. tadorna does not consist of head and neck dipping as in geese, but of a simultaneous dive by the two sexes during which the male mounts the female. In Alopochen and Chlophaga copulation may occur in shallow water or even on land. The food of most species consists of grass and water plants (eelgrass, kelp), but a few forms, particularly T. tadorna, feed also on mollusks, shrimp, and other water animals. The grazing habits of the five species of Chlophaga are correlated with a Branta-like bill, as in Cyanochen and Neochen. The color pattern of the downy young, the wing pattern (with metallic specu- lum) of the adults, the asymmetrical development of the bulla ossea J. Delacour THE FAMILY ANATIDAE 13 Ernst Mayr of the syrinx, the sexual dimorphism in voice, the scutellation of the tarsus, and many other features prove the relationship of Chlophaga with the sheldrakes. The species of this tribe form a graded series from long-legged birds with a narrow bill, as in Chlophaga, to birds which have shorter tarsi and a longer, broader bill with more distinct lamellae, as in Tadorna. The gap between the sheldrake tribe and the river ducks seems to be bridged morphologically by such intermediate forms as Lophonetta specularioides on one side and Anas specularis and A. acuta on the other. However, sheldrakes have larger tails than river ducks, and their legs are longer and placed more forward; they also differ strikingly in their habits. It is therefore justifiable to keep them in a separate tribe. The Cape Barren Goose (Cereopsis novae-hollandiae) is a peculiar bird, quite different from typical sheldrakes in many respects, in- cluding skull, bill, and color pattern of the adult. The tarsus is reticulate and the syrinx without bullae, both characters indicating a primitive condition. On the other hand, the color pattern of the downy young, the general proportions of the birds, their posture (Figures 7 and 8), as well as their quarrelsome temper, indicate relationship with Chlophaga, as Heinroth (1911) pointed out many years ago. The real place of this primitive genus in the duck family is still somewhat uncertain. The sexes are alike in plumage. The voice of the male is loud and trumpeting, that of the female a low grunt. The bill is short and thick, covered for the greater part by a yellow cere. The nest is placed on the ground. All the South American "geese" of the genus Chloaphaga (Figures 8 and 9) are nearly alike in shape and habits. The males have a high-pitched whistle, the females a harsh quack, very similar among all species. Their breeding display is interesting, distinctly like that of the typical ducks. The male stands erect, throws the breast forward, ,the neck backward, and calls, while slightly lifting the wings; the female quacks with lowered head and a vertical movement of the neck. In the Andean species (C. melanoptera), the display is more elaborate, and both sexes puff out their feathers; the voice is softer. There is an eclipse plumage in C. poliocephala, grayer and less bright than the nuptial, between the postnuptial and the late fall molts, affecting both sexes. The sexes are similar in plumage in three species (rubidiceps, poliocephala, melanoptera), different in the other two (hybrida and picta3). The downy young of the various species (Figure 9) are similar to one another in pattern, but some have very dark gray marking (poliocephala and melanoptera); others are paler and browner (picta and rubidiceps); while in hybrida they are ex-  We include in picta both dispar and leucoptera. For the use of the name picta instead of dispar or leucoptera, see Itellmayr, 1932, Field Mus. Nat. Hist. Zool. Series, 19:319. March 1945 14 THE WILSON BULLETIN Vol. 57, o. I tremely pale. The metallic speculum in Chlophaga is formed by the greater wing coverts, while the secondaries are white. The Abyssinian Blue-winged Goose (Cyanochen cyanopterus) could almost be considered congeneric with Chlophaga, differing only in its slightly flatter bill, its more graduated tail, its blue wing coverts, its metallic green secondaries, and its alarm display. The voice in both sexes resembles that of Chlophaga melanoptera, but is still softer. As in C. melanoptera, the face of the downy young shows during the first days after hatching a distinct golden tinge, a feature found only in these two species of the tribe. When alarmed, cyanopterus puffs out its shoulder feathers and rests its neck among them. Otherwise, it has the same general aspect, habits, and display as the species of Chlophaga. The Egyptian (Alopochen) and Orinoco (Neochen) Geese are re- lated, the bill in Neochen being slightly, and in Alopochen decidedly, flatter and broader than in Cyanochen and Chloaphaga. The male Orinoco whistles, whereas the male Egyptian emits a husky breathing sound. In addition to this difference in bill and voice, the plumage pattern of adults and the coloration of the downy young are different, as well as the display postures. It may, therefore, be justifiable to recognize the genus Neochen. (The Orinoco Goose and downy young are shown in Figure 10.) Both females have harsh quacking voices. Their displays, although special in each case and very elaborate in Neochen, recall those of Chlophaga, except that the wings are opened a little more. The nest is placed by preference--particularly by the Orinoco Goose--in a hollow tree or in a hole in the ground, but always in some sheltered site. The sexes in both species are alike. The typical sheldrakes are usually placed in two genera, Tadorna and Casarca. The two type species, tadorna and ferruginea, the European representatives of these groups, are indeed strikingly dis- similar. However, they are connected by a chain of intermediates. The Australo-Papuan species radjah, for example, has the body shape, syrinx, and downy plumage of "Casarca," the whistling voice of "Tadorna" in the male, a bill and plumage pattern intermediate be- tween the two "genera," and it nests in trees, which neither typical Tadorna nor typical "Casarca" do. The Australian tadornoides ap- proaches Tadorna in color pattern. It is best for this reason to group all of the typical sheldrakes in a single genus, Tadorna, in which we also include "xPseudotadorna" cristata. This probably ex- tinct Korean form resembles Lophonetta in having a slight crest and a rather graduated tail, but in every other respect it agrees perfectly with the other species included in Tadorna. The species of Tadorna have a flatter bill (slightly curved, with distinct lamellae) and shorter tarsi than the goose-like species described above. Both sexes in the four species formerly separated J. Delacour THE FAMILY ANATIDAE 15 Ernst Mayr as "Casarca" (ferruginea, cana, tadornoides, variegata) have a loud voice, which they use very often in duets; that of the female is very different from the male's--harsh and quacking. The display re- sembles that of Chlophaga and particularly that of Alopochen. The male moves his erect head backward and forward; the female stretches her neck and keeps her head low as in most other Tadornini. They nest in holes and burrows. An interesting fact is that the juvenal plumage of both sexes resembles that of the adult male. It is always different from that of the female although not conspicuously so, except in one species (variegata), in which the female has a distinct, blackish, eclipse plumage. The Common Sheldrake (tadorna) differs from the other species primarily in the whistling voice of the male and the showy black, red, and white plumage. It is also less quarrelsome and more gregarious. If associated with them in captivity, T. radjah pairs with T. ferruginea (with which it produces fertile hybrids), but completely ignores tadorna. The South American Lophonetta specularioides resembles the mem- bers of the genus Anas in its plumage pattern. But in its quarrelsome, solitary habits, its display and general behavior, and the pattern of the downy young, it is undoubtedly a member of the sheldrake tribe. It provides an obvious link between the tribes Tadornini and Anatini. The large, robust, and plain-colored steamer ducks (Tachyeres) of the austral coasts of South America are difficult to place. We have long observed them at Clres. They have almost no display, and their habits and voice seem to be very simple and primitive. They are great divers and superficially resemble the eiders to which, however, they are obviously not related. They are exceedingly quarrelsome and combative, as are many genera of Tadornini. The color pattern of the downy young is characterized by a broad white stripe (interrupted in pteneres) along the side of the head, rather similar to the pattern of the young in Chlophaga. It is possible that the steamer ducks are diving species evolved from the Chlophaga group, and we therefore tentatively associate them with the Tadornini. The male steamer duck helps the female in raising the young, and there is some evidence that steamer ducks pair for life. This habit would also favor classification with the Tadornini. The male has an asymmetrical bulla ossea of the syrinx, like that found in the Tadornini, Anatini, and Cairinini. The secondaries are white, as in Chlophaga. As Murphy has convincingly demonstrated (1936, "Oceanic Birds of South America," pp. 951-972), there are three species of steamer ducks, a flying species (patachonicus) and two flightless ones (pteneres and brachypterus). March 1945 16 THE WILSON BULLETIN Vo. 57, o. i 2. TltlBE ANATINI. RIVER DUCKS The river ducks, also called surface-feeding ducks, occupy a central position among the Anatinae, between the sheldrake tribe of mostly grazing species and the diving tribe of pochards. We recognize about 36 species of typical river ducks and 4 aberrant species which we classify with them only tentatively. River ducks differ from the sheldrake tribe most noticeably in their smaller, more pointed tail; the legs are shorter and are placed farther back on the body, which is the reason for their waddling walk. They go to the shore or ice to rest more frequently than the pochards or sea ducks do. The wings are long and pointed and are beaten less rapidly than among the pochards and sea ducks. The hallux is not lobed. The syrinx of the male has an asymmetrical bulla (always on the left side), which is evenly ossified. The sexual dimorphism of the syrinx is correlated with a pronounced difference in voice between the sexes, the voice of the female usually being louder. All river ducks have two molts each year. In about half the species the plumages of the two sexes are dull colored and very similar; in a few species (e.g. Chi16e Widgeon, Anas sibilatrix) both male and female are brightly colored. There is strong sexual dimorphism in the brighter forms of the northern hemisphere and in some southern forms; in these species the nuptial plumage of the drakes is very dif- ferent from the eclipse plumage, which resembles that of their females. In the dull-colored species (and in the species in which both sexes are bright), there is very little difference between the nuptial and eclipse plumage (Falla and Stead, 1938). The female and eclipse plumages of the brightly colored species have a hormonal basis. Castrated males and females of such species wear the nuptial plumage of the drake throughout the year. All species have an iridescent metallic speculum. The downy young of all species of the genus Anas are very much alike (similar to those of the mallard). They are usually yellow and brown with a dark line across the eye. Most river ducks live on fresh water, but a few species nest on the seashore; some are found on the ocean during migration. They get most of their food in shallow water, securing it from the surface; or from mud with quick dabbling motions of the mandibles; or, where water is slightly deeper, by "up-ending" (tipping) with head and front part of body submerged and tail in air. Young dive fairly freely, but adults only exceptionally or if wounded. Anas sparsa alone among typical river ducks is reported to dive regularly. Only a few species perch in trees and nest in holes. All river ducks breed when one year old. They have larger clutches than the pochards, but the eggs are smaller. The typical river ducks consist of 14 groups, characterized by minor morphological and biological peculiarities, but all closely re- lated and more or less connected by intermediates. One must either I. Ddacou THE FAMILY ANATIDAE 17 Ernst Mayr recognize 14 separate genera or unite all these species in the single genus Anas. The latter arrangement, originally proposed by Hartert, has largely been adopted by Phillips, leters, and Witherby, but, curiously enough, all of these authors have kept the shovellers in the separate genus Spatula. The extremely close relationship of the four species of shovellers with the three "teal" of the blue-winged group (querquedula, discors, cyanoptera) is, however, evident and has been emphasized by many authors. All these species have an almost iden- tical color pattern of the wing. The peculiar courtship habits, the feeding methods, and sometimes the voices are similar among the species and somewhat different from those of the other river ducks. The only difference between "Querquedula" and "Spatula" is the larger body and bill in the shovellers. Furthermore, there is good evidence that the shovellers are not even a natural, monophyletic group. In two pairs of species, the South American Shoveller (platalea) and the Cinnamon Teal (cyanoptera) on one side, and the Australian- New Zealand Shoveller (rhynchotis) and the Blue-winged Teal (discors) on the other, the "teal" of each pair agrees in plumage color with the "shoveller" to such a surprising degree that the closest relationship must be assumed. This suggests that the shoveller group is polyphyletlc, owing its origin to the repeated development of large- sized and large-billed species from the original blue-winged duck stock. Again, as in so many other cases in arian taxonomy, the shape of the bill has been a very misleading character. In addition to Spatula, leters also maintains the genera Mareca (for the widgeons) and Chaulelasmus (for the gadwalls), but this action is, in our opinion, not consistent with the lumping of the other groups. The display among the river ducks follows a common pattern, but it shows every degree of elaboration from a few simple perfor- mances to a complicated series of displays. These more or less elab- orate displays, which are accompanied by distinctive calls, provide ex- cellent clues to the relationships among the various species, even better ones than color patterns and morphological features. lursuit flight is common with most species. The most elaborate display is that of the Mallard (Anas platy- rhynchos). It may be described in detail, to form a basis of comparison with other species. It consists of a series of postures, the principal of which are: (1) Swimming around the female, or sitting on the water with other drakes, with head sunk, the feathers puffed out, and neck resting on the back; tail shaken and raised and head shaken repeatedly. (2) Quick "throw-up" Of head and tail, at once followed by No. 3. (3) Neck stretched out over the water, the bird swimming about swiftly in various directions. (4) Following posture No. l, the bill is suddenly lowered and dipped in water; the bird then stands up and rapidly passes its bill up his breast, producing a jerk which throws up a small jet of water as bill is withdrawn. A whistle is March 1945 18 THE WILSON BULLETIN Vol. s7, o. i emitted during this display. (5) The drake swims around with neck raised and head slightly turned, as the female displays at his side. The female follows the male, quacking, with head lowered and re- peatedly moved sidewise away from the drake as if to defy others to approach her mate. She also assumes posture No. 3 of the males. In all typical Anatini, the precopulation display in both sexes con- sists of a bobbing up and down of the head, the bill touching the water at its lower course and always remaining nearly horizontal. Finally, the female flattens herself, extends her neck, and is mounted by the male. In species most nearly related, these postures are re- produced with only minor changes or omissions. In other groups, some or most of the postures are lacking, while in still others the display is very simple and primitive or considerably modified (blue- winged ducks). Making use of all these characteristics, we arrange the 36 species of river ducks of the genus Arias in a number of groups which were given subgenerlc rank in an earlier publication (Delacour, 1936). In order to avoid complicating the nomenclature, we refrain from listing subgenera here. This does not mean, however, that we do not fully recognize the validity of these subdivisions of the genus Arias. Group 1. The Bronze-winged Duck The Bronze-winged Duck (Arias specularis) of South America, the only member of this group, remains poorly known. We have never observed it in life. Although in its plumage it resembles the Crested Duck (Lophonetta specularioides) of the same region, it seems closer to the river ducks in its general proportions. So far nothing is known of the habits, voice, and courtship display of this species. Recent observers report that it is a sociable bird, gathering in flocks. Its present place in our system is tentative. Group 2. Salvadori's Duck Salvadori's Duck ("Salvadorina" waigiuensis), from the mountains of New Guinea, is very close to the birds of the following group in its proportions and color pattern. Its reputed adaptation to life in rapid mountain streams has been greatly exaggerated, and it shows no resemblance to the Torrent Duck (Merganetta); the tail feathers are hardly stiffer than those of other ducks. The bill is fairly broad, and the head is entirely black. Otherwise the species agrees very well with birds of Group 3. The habits are those of typical river ducks (Mayr and Rand 1937, lull. Amer. Mus. Nat. Hist., 73:9-12). Group 3. "Tropical Pintails" A group, inhabiting tropical and subtropical countries, which con- sists of species that are very near the pintails of Group 4 though less J. Delacour THE FAMILY ANATIDAE 19 Ernst Mayr specialized, can be called the "tropical pintails." The tail is pointed but shorter; the male's voice is lower and less melodious; the display resembles that of the pintails of Group 4 but is simpler, lacking the more elaborate postures to a varying degree according to species. Male and female are alike in all species, and the eclipse plumage resembles the nuptial. The following six species belong to the group: angustirostris, capensis, punctata, versicolor, erythrorhyncha, and bahamensis (with subspecies galapagensis). They all have a com- paratively large head, dark above, pale below; a thin and rather long neck; a narrow and fairly long bill, which is depressed, curved, and always brightly colored. All have a speculum, bronze-green with light-brown borders, except in angustirostris, where it is whitish gray. The latter is a pale species, but its shape and general plumage pat- tern indicate clearly its relationship to the others, particularly to capensis. The males of A. versicolor and of A. punctata are practically voiceless, and the male of versicolor has, according to Heinroth (1911), a peculiar enlargement of the middle of the trachea. Group 4. Pintails The Common Pintail (Anas acuta) is very similar to the mallard in general habits and display. In courtship posture No. 2, the tail is raised vertically; posture No. 3 is usually omitted. The call of the drake is a soft klyck, very much like that of the green-winged teals (Group 5). Like the mallard it emits a whistle during Posture 4 of the courtship. Eaton's Pintail (eatoni) is colored like the eclipse plumage of acuta and is obviously conspecific with it, differing mostly in its smaller size. The close relationship of acuta with the mallard is indicated by the frequent crossing of the two species and by the almost unlimited fertility of the hybrids. Pintails seem to indulge in "up-ending" more than any other duck, the greater frequency of this habit being undoubtedly correlated with the longer neck of the species. The South American Brown Pintail (A. georgica spinicauda) has a yellow bill and throughout the year a spotted fulvous-brown dress in both sexes. The South Georgian Pintail (A. g. georgica) is very similar but much smaller and slightly darker. Voice and display are those of acura. Group 5. Green-winged Teals The Green-winged Teal (Anas crecca) has the same display as the mallard, and its voice, a soft klyck, is emitted during Postures 2 and 4 of the courtship. It is represented in South America by the Yellow- billed Teal (A. fiavirostris) which resembles in plumage the South American Brown Pintail (Group 4). The two forms, together with A. undulata (Group 9), differ from their brightly colored northern repre- sentatives (A. crecca, acuta, and platyrhynchos) in a remarkably parallel manner. March 1945 20 THE WILSON BULLETIN Vol. s?, o. i Group 6. Baikal Teal The color pattern (Frontispiece) of the Baikal Teal (Anasformosa) indicates that it is related to crecca. However, voice and display are entirely different and necessitate its separation in a special group. Group 7. Falcated Teal The Falcated Teal (Anas falcata) of northeastern Asia also stands rather alone. It is perhaps more closely related to the Baikal Teal than to any other group. Its voice, a triple whistle of the pitch of crecca, is given without special display. Head and neck are pressed close to the body, and the remarkable sickle feathers of the male are, curiously enough, never displayed. This species seems to be also re- lated to the Gadwall (A. strepera), which it approaches in several ways and whose company it seeks in captivity. Group 8. Austral Teals A group standing near the mallards is composed of teals from the South Pacific and the Indian Ocean. The relationship of the two groups is shown in a general similarity in shape and in color pattern. Both include some forms with green-headed, bright males, having a distinct eclipse plumage, and some that are dull-colored. The display of the Austral teals is that of the mallards minus the elaborate Pos- tures 3 and 4. They all have the same wing pattern, with a brilliant dark green and white speculum. It is a perching group, often nesting in trees. It is composed of two species with a marked sexual di- morphism: "Nesonetta" aucklandica 4 (including Anas cklorotis as a subspecies) and castanea; and two that have a dull brown plumage: gibberifrons (including albogularis and several other subspecies) and the small erythristic bernieri, a rare bird of Madagascar. S. D. Ripley (1942, Auk, 59:90-99) has recently studied gi}- berifrons and concluded that it was conspecific with castanea. It is obvious that both forms are very closely related; but it seems that both often breed at the same locality, and we therefore prefer to consider castanea a full species. Hybrids reared in captivity are inter- mediate and completely fertile. Group 9. Mallards The mallard group is composed of the well-known northern bird, with a brilliant nuptial and inconspicuous eclipse plumage, and of many other species spread over most of the world except South America. These other species have a dull brown plumage practically the same in the two sexes and in the two annual plumages. The entire group could almost be considered a single superspecies. It is only in North America and East Asia that the breeding ranges of two species of this group overlap. It appears that this overlapping is of recent date and perhaps brought about by human agency. In general behavior, display, and voice, the mallards are alike. It is 4 We fllow Stead (1938, Trans. roc. Roy. So. Nv Zealand, 68:100-101) in placing Xenonetta nesiotis Fleming, 1935, in synonymy here. I- Ddacour THE FAMILY ANATIDAE 21 Ernst Mayr however, possible to distinguish several groups among them according to their plumage pattern and general proportions, and we find it expedient to accord specific status to each of these groups. The Hawaiian Duck, Laysan Teal, and Marianas Mallard (wyvil- liana, laysanensis, and oustaleti) are small and have lost in their isolation many of the characteristics of the mallard. Still, they are certainly nothing but dull-colored editions of the Common Mallard (platyrhynchos) and therefore conspecific with it; all have the same speculum as the Common Mallard. The East Asiatic-Pacific group, which includes poecilorhyncha, superciliosa, and luzonica, as well as other less distinct forms, also constitutes a single species, all the forms being very similar in plumage pattern and shape. The Mada- gascan Meller's Duck (mdleri) stands alone, as does the African Yellow-billed Duck (undulata); the latter reminds one of the South American Brown Pintail (A. georgica spinicauda) and of the Yellow- billed Teal (A. fiavirostris) by the colors of its bill and plumage, as noted above. The North and Central American group can also be considered as forming one species (fulvigula); it seems obvious that the Mexican and Black Ducks (diazi and rubripes) are only sub- specifically distinct from the Dusky Duck (fulvigula). Group 10. African Black Duck The African Black Duck (Anas sparsa), a forest species, stands quite alone in its behavior and habits. It is a quarrelsome species leading a solitary life. Its display is different from that of the other groups and is simpler; its voice is peculiar. This species is probably less closely related to the mallards than is commonly supposed; it requires further study. Group 11. Gadwall The display of the Gadwall (Anas strepera) is similar to that of the Mallard but is simpler. Posture 4 is usually absent, and instead, a grunting call is uttered without special body movements except that the head is raised. The display performance is more casual and the voice of the female much less loud than in Groups 2, 3, and 7. Group 12. Widgeons. The three species of widgeons form quite a special group, not closely related to any other. Their display, although it suggests cer- tain parts of that of the mallards, is peculiar. It consists mostly of a lifting of the long scapulars and the primaries accompanied by loud whistling and vertical movement of the head. It is interesting to note that the South American species, sibilatrix, in which the two sexes are nearly similar and both brightly colored, has the most elaborate postures. In the European Widgeon (penelope) and the American Widgeon (americana), which are very closely related, this display occurs in a more rudimentary form. However, the American species lacks the loud whistle, produced before and during the breeding March 1945 22 THE WILSON BULLETIN Vo. s7. o.  season, which the European species shares with sibilatrix. It seems that in sibilatrix the drake helps the female take care of the young, and similar cases have been reported in americana and penelope, although it does not appear to be the rule with them. This trait is apparently unusual for the genus Arias, but parental care of many species of river ducks has been studied insufficiently. The somewhat isolated position of the widgeon is also indicated by the color of the young (which are less yellow than the others) and the apparent sterility of hybrids with other species of Anas, except strepera (Group 11). The pair among widgeons is a more closely knit unit than in other groups, and although pursuit flight occurs, it is infrequent. Group 13. Blue-winged Ducks We now come to a very well-defined group of species which may be called the "blue-winged ducks." They include the birds known as the blue-winged teals (discors, cyanoptera, querquedula) and the shovellers (platalea, smithi, rhynchotis, clypeata). The plumage pat- tern is consistent throughout the group, particularly the blue-gray color of the lesser and median wing coverts. Indeed, as we have said above, some of the species are very similar in plumage and differ mainly in body dimensions and bill size (discors and rhynchotis; cyanoptera and platalea). There are only minor differences in habits and display among the forms. They have a peculiar ceremony in which one or several pairs swim around in a circle, head to tail, merry-go-round-like, with the bill immersed and water running through it as if in a cooperative effort to stir up food. The same per- formance, in a formalized manner, occurs also as a courtship display. Another type of display is very simple, consisting in a rhythmical raising and lowering of the head by both male and female with the bill kept horizontal. ?ursuit flight of several males after one female is of frequent occurrence. In the teals, querquedula, discors, and cyanoptera, the bill is long, but of normal shape; the voice of the drake is a harsh or whizzing clatter. The shovellers are larger and have the well-known huge spatulare bill. Three species (clypeata, rhynchotis, and smithi) are similar in size, and the voice of the male is a low, short hoot: took-took. The South American Shoveller (platalea) is smaller and has a smaller bill; the male has a low, whizzing voice. We have found that when the Blue-winged Teal (discors) and the Cinnamon Teal (cyanoptera) are associated artificially they interbreed freely, producing fertile hybrids; and the stock soon becomes hopelessly mixed. The Common Shovel- ler (clypeata) and the Australian-New Zealand Shoveller (rhynchotis), as well as the three allied teals, have an eclipse plumage. The South American Shoveller (platalea) and Cape Shoveller (smithi) have no noticeable one. The Garganey drake (querquedula) is unique in the tribe in not acquiring its nuptial dress until late winter. All Cin- J. Delacour THE FAMILY ANATIDAE 23 Ernst Mayr namon drakes have an eclipse plumage, whether they come from North or South America. We made a point of importing birds from both continents to make certain of this fact, which had been questioned. It may be that the blue-winged ducks are linked to other river ducks through Arias versicolor (Group 3), whose wing pattern is very like that of the blue-winged group. Group 14. Ringed Teal A very puzzling species is the small Ringed Teal (Anas leucophrys), of South America. In its shape and general proportions, it is a normal Anas. Its plumage pattern and coloration, different in the two sexes, but very elaborate in both, is peculiar. Although the plumage of the male is very bright, it is not changed into an eclipse plumage after the breeding season. This is a perching, hole-nesting duck. In its display and courtship habits, it differs entirely from all other river ducks and resembles the pochards (Aythyini). As in those diving ducks, the female's call is a low, harsh, short, repeated kur-r-r. The male has a deep, soft whistle, which he emits while jerking back the neck, which is distended with air. He also indulges in the curious mock pursuit of the female, so typical of the pochards. Because of these strikingly different habits, Delacour (1936:369) placed the species in a special subgenus Calonetta. A better under- standing of this little-known species may result in its generic sepa- ration. Aberrant River Ducks The curious Blue Duck (Hymenolaimus malacorhynchos) from New Zealand, with its peculiar coloration and bill, may be merely an aberrant Anas. It certainly belongs to the river duck group and shows no resemblance whatsoever to the Torrent Ducks (Merganetta). It is difficult to understand how such a suggestion could have ever been made. Its behavior is not well known, but it is reported to be able to dive. The downy young have a dark line through the eye as in the genus Arias. The small Australian Pink-eared Duck (Malacorhynchus mem- branaceus) recalls in its plumage pattern and coloration the tropical pintails (Group 3), particularly the Marbled Teal (angustirostris). It has a white, not metallic, speculum. The large, peculiar bill differs widely from that of the shovellers and gives no due to the systematist. The habits are little known and require further study before this duck can be assigned its proper place in the sequence of species. Another puzzling species is the rare Pink-headed Duck from India (Rhodonessa caryophyllacea). It differs widely in coloration from all other ducks, with its blackish body, reddish-fawn speculum, pink head, pink hind neck, and bill. For many years we were able to ob- serve live specimens in the collections at Cl[res and at Foxwarren, after Mr. A. Ezra had obtained a number of them from Calcutta. March 1945 24 THE WILSON BULLETIN Vo. s7, o.  These captive birds never nested, but they constantly displayed dur- ing the breeding season. The display of the drakes was simple: they puffed out the head feathers, with the neck shortened and resting on the back, then stretched the neck upward as they uttered a whizzing noise resembling the whistle of a mallard, though lower and weaker. The females showed in a rudimentary way the usual posture of river ducks. Because of the resemblance in display and posture, we consider this species as belonging to the present tribe. It has certainly no con- nection with the perching ducks, though one has often been suggested. The Freckled Duck (Stictonetta naevosa), from Australia, is an aberrant, primitive species that defies any attempt at classification. In its general body build it seems to be closest to the river ducks, but the freckled color pattern and absence of speculum are peculiar, and the tarsus is reticulate in front. The trachea is quite different from that of the other river ducks. The bulla is absent, but the trachea has two expansions in the male. The color of the downy young and the various phases of the display have not yet been described. The food is obtained on the surface of the water, not by diving. Leg position of (a) scaup and (b) mallard (a#er Heinroth). 3. TRIBE AYTHYINI. POCHARDS This small tribe is composed of 14 species of fresh-water diving ducks. They are closely related to one another but can be divided into two genera. The color of the downy young and other characters indicate that the pochards are much more closely related to the river ducks than to the sea ducks. They are characterized by a short, heavy body, a rather big head, and large feet. The legs are placed far back and laterally; the hallux is lobed. Sexual dimorphism is always present, but is sometimes not very pronounced. The males of all the temperate-zone species have an eclipse plumage which is usually intermediate between the nuptial J. Delacour THE FAMILY ANATIDAE 25 Ernst Mayr and the female plumage. Metallic colors do not occur on the wing, the speculum being either white or pale. The syrinx of the male has an asymmetrical bulla, but it is quite different from that of the river ducks; it is pointed rather than roundish, is more or less chambered inside, and has membranaceous windows on the outside. The downy young resemble those of many river ducks in color and pattern, but the yellow pigment is usually pronounced, and there is no distinct dark line through the eye. The heads are larger, even in the downy young, the legs and feet sturdier and set farther back on the body. Pochards come on land rather infrequently except for nesting; they walk clumsily. They are good divers although they usually do not stay under water so long as the sea ducks do. The food is primarily vegetable, but in certain species (Tufted Duck and scaups), and at certain seasons, the animal component prevails. All members of this tribe breed in their first year. The nest is placed on the ground among reeds or in the grass. The display of pochards differs greatly from that of the river ducks and other tribes. The drakes have the curious habit of pur- suing their own mates in a rough way. We have already referred to this mock brutality in connection with Anas leucophrys. The drakes in most species call very rarely. Females utter a loud karr. There is little basic difference among the displays of the various species of the tribe. Hochbaum (1944:22-45), who describes the display in considerable detail for the Canvas-back ("Nyroca" valisineria), distinguishes four main postures of the displaying drake: (1) The "head-throw," during which the head is first thrown sharply backward until the top of the head touches the back and the throat points to the sky. Then after a brief, almost imperceptible pause, the head is snapped abruptly forward to swimming position. The call ick, ick, 1/2ooo is usually uttered during this motion. (2) The "neck-stretch," during which the drake raises his head as high as the stretched neck will permit and parades stiffly before the hen and the other drakes. (3) The "sneak," in which the drake stretches head and neck horizontally on the water. (4) The "threat," in which the drake swims in a crouched position, usually when ready for a fight. The "head-throw," during which the neck seems to be inflated with air, apparently occurs in one form or another in all the species of this genus. The genus Netta is composed of three species inhabiting temperate and subtropical regions. They constitute a bridge between the river ducks and the more specialized pochards of the genus Aythya 5 being less well adapted to diving than the latter. The body is longer and narrower, the legs longer and more slender, the bill narrower, than in Aythya, and the birds are less heavy and clumsy on land. All three s Aythya has priority over Nyroca and is not preoccupied by Aethia (see Witherby et at., 1939:286). March 1945 26 THE WILSON BULLETIN Vol. s7, No. i species have bright red eyes. They are the Red-crested Pochard (Netta rufina) of southern Europe and central Asia; the Rosy-billed Pochard of Argentina ("Metopiana" peposaca); and the Southern Pochard ("Nyroca" erythrophthalma) 6. The species rufina and pepo- saca are usually placed in separate monotypic genera, while erythroph- thalma is united with Aythya on account of a similarity in color to several species of that genus. But in its proportions and its plumage pattern erythrophthalma is obviously close to peposaca. The display of these two species is on the whole that of the other pochards, except that peposaca sometimes calls with neck vertical and bill point- ing skyward. The male Red-crested Pochard (rufina) has rather dif- ferent postures, particularly one in which it spreads its long head feathers, depresses the bill, and rests the neck on the back while uttering a sneezing call. This resembles a simple phase of the display of the mallard. The trachea of rufina has two bulbous enlargements. The genus Aythya contains four groups: The first consists of the closely related Canvas-back (valisineria), the European Pochard (ferina), and the Redhead (americana). The European Pochard in coloration is intermediate between the other two, but in the shape of its head it is nearer to valisineria than to americana. Group 2, the white-eyes, contains the four species, innotata (Madagascar), nyroca (Eurasia), baeri (east Asia), australis (Australia and New Zealand), all from temperate and subtropical lands. Although superficially simi- lar, their postures and proportions are different enough to justify considering them separate species. The black and white Tufted Duck (fuligula), from Eurasia, and the Ring-neck (collaris), from North America, are certainly related to each other, and they form a third group which includes also the New Zealand Duck (novae-seelandiae). Group 4 consists of the scaups. The Greater Scaup (marila), which ranges all over the northern hemisphere, is the most heavily built bird and ablest diver of the tribe and the only one that spends much time on the ocean. The Lesser Scaup (afl2nis), restricted to America, is closely related. The scaups apparently take a higher proportion of animal food than the other species of the pochard tribe. 4. TRIBE CAIRININI. PERCI-IING DUCKS This very peculiar group of ducks had already been separated by Salvadori, as a subfamily (Plectropterinae), and, in our opinion, it was a mistake of modern authors to remove from it the Mandarin ("Den- dronessa" galericulata) and the Carolina Wood Duck (Aix sponsa) and place them among the river ducks. In their general proportions and 0 The Southern Pochard has a curious distribution in East and South Africa and in South America, where it is currently stated to inhabit only the northwestern parts. But it evidently occupies a much greater area, for a number of live specimens were received at Clres in 1938 from the neighborhood of Pernambuco, eastern Brazil. . I. Ddacour THE FAMILY ANATIDAE 27 Ernst Mayr shape, in habits and behavior, they clearly belong to the perching ducks. To the 14 species listed by Salvadori, several of which we relegate to the rank of subspecies, we have added three more. One of these is the very aberrant Pied Goose (Anseranas); peculiar as it is, it resembles the Spur-winged Goose (Plectropterus) in general aspect and habits; it appears to be certainly nearer to that than to any other species of Anatidae. We also consider the Brazilian Teal (Amazonetta) a member of this tribe on account of the general pro- portions of its wings and tail, the position of its legs (alike in adults and young), its voice, display, and its living and nesting habits. Finally, we place here, provisionally at least, the small aberrant Australian Maned Goose (Chenonetta jubata). It has usually been considered allied to Chlogphaga (Tadornini), but its behavior and habits, as well as the pattern of the downy young, which is very similar to that in the Mandarin Duck and totally different from those in the sheldrake tribe, indicate that it would be a mistake to leave it with the sheldrakes. The nearest relatives of the perching ducks seem to be the river ducks. The two groups resemble each other greatly in the coloration of the downy young and in the structure of the syrinx. Hybrids between species of the two tribes are sterile, but females of the Mal- lard X Muscovy cross sometimes lay small eggs. Serological tests confirm this relationship (Sokolovskaia, 1936). Species such as Amazonetta brasiliensis, 7 Aix sponsa, and Aix galericulata seem to bridge the gap between the river ducks and the perching ducks. The perching ducks spend more time in trees than any others, and most of them nest in holes high above the ground. They are decidedly forest ducks. Correlated with these habits are their un- lobed well-developed hallux and their sharp, strong claws. The legs are set more forward than in the river ducks, in fact even more than in the geese and the sheldrakes. The length of the tarsus varies from very long (e.g. Plectropterus) to extremely short (e.g. Nettapus). The bill is rather thick and never depressed, often very strong, with a large nail. The rectrices are wide and long, and the tail is only slightly graduated, never pointed. The wings are very broad and brightly colored. The scapulars, secondaries, and particu- larly the terriaries, are notably developed. In a number of species metallic colors occur extensively in the plumage, although there is no sharply defined speculum; the terriaries and wing coverts are metallic or of a bright color. A bony, spur-like knob at the bend of the wing is more or less well developed in most species. The young are remarkable for their long, stiff tails and their ability to climb. They have no very particular pattern of down; all are brown and 7 Arnazonetta vittata Derscheid, 1938, is apparently a synonym (see Zimmer and Mayr, 1943, Auk, 60:250). March 1945 28 THE WILSON BULLETIN vol. s, No. i yellow, except those of the pygmy geese (Nettapus), and have an eye-line. With the exception of the two species of Aix, perching ducks inhabit the tropics and subtropics. Their display is usually very simple, almost nonexistent, consisting mainly in a forward and back- ward movement of the head with neck extended. In general, the voice of the drake is a low, squeaking or aspirated, whistle, and the female quacks harshly. Many species are remark- ably silent. Only three species have an eclipse plumage. In most perching ducks, the female is rather similar to the male, but in some cases it is strikingly smaller. Many of the species, if they pair at all, seem to have very weak mating ties. It is only with great reservations, as we have said before, that we list among these birds the queer and primitive Australian Pied Goose (Anserarias semipalmata) in which the two sexes have a loud voice and are alike except for a slight difference in size. There is no sign of a real display in this species. They perch high up, an action facili- tated by their semipalmate feet and long hallux, and they spend much time on trees. They appear, however, to nest on the ground, among rushes. They have long legs, a powerful bill, and a bald fore- head, resembling Plectropterus in most of their features (Figures 11 and 12). Anserarias differs from all other Anatinae, except Cereopsis and Stictonetta, in its reticulated tarsi, thus approaching the Anserinae. It is unique among the Anatidae in having a gradual wing molt. The downy young resembles that of Plectropterus. The African Spur-winged Goose (Plectropterus gambensis) is also long-legged, has a bare forehead, adorned with a knob, and big spurs on the bend of the wing. We have seen scores of them perching on small limbs high up in large trees in West Africa. They are reported to lay usually on the ground, but also in old nests in trees. The male has a curious high-pitched voice, which it uses incessantly, though the female seems almost mute. They have a small bulla on the syrinx. They are extremely aggressive and sometimes injure other waterfowl considerably with their sharp spurs. The Comb Duck (Sarkidiornis melanotos) includes two well- marked subspecies, one (melanotos) extending from Africa to south- east Asia (Figure 13), the other (carunculatus) inhabiting South America. We have observed at Clres that the racial hybrids are not intermediate. In such hybrid broods some birds look like pure melanotos and others like pure carunculatus. Comb Ducks have legs of moderate length; they perch freely and nest in tree holes. No pair formation seems to exist, the males pursuing and mating with any available female as the Muscovies do. The difference in size between the drake and the duck is truly astonishing. Both sexes are almost mute, the male having a weak whistle and the female a low grunt. The display of the male, which is also his challenge, consists in lifting I. ldacour THE FAMILY ANATIDAE 29 Ernst Mayr the neck and chest, with wings slightly raised, the head slowly moved from side to side, the neck curved and dipped downward at frequent intervals. According to Heinroth, the male initiates his pursuit of females often with "dipping" displays such as occur in the geese. The female has no display whatever, according to our observations at Clres. Contrary to current descriptions, the downy young are brown and yellow, much like those of Cairina and _Pectropterus, and have no white or other distinctive head markings. Erroneous de- scriptions found in the literature seem to have been based on wrongly identified specimens in the British Museum. We consider that the three large, tropical, short-legged forest species which biologically replace one another in America (Cairina moschata), Africa (".Pteronetta" hartlaubi), and southeast Asia ("Asarcornis" scutulata) are congeneric. All have the same propor- tions of the body, wings, tail, bill, and feet. The males of all three have, in the breeding season, a swollen knob at the base of the bill; they agree fairly well in general pattern and perfectly in that their wings all have a showy patch formed by the upper wing coverts. The males are considerably larger than the females, although the dif- ference is not so striking as in the Comb Duck. The two sexes are similar in coloration. The habits of the three species are very much alike; they spend a great part of the day perched on large trees, in the holes of which they nest. They appear to be promiscuous, although more remains to be learned of their behavior in a wild state. They are very quarrelsome. When the characters invoked for the generic distinction of these three species are examined, they appear quite insufficient, and we therefore consider Asarcornis and Pteronetta as synonyms of Cairina. The Muscovy Duck (Cairina moschata), common in Central and South America, is the best known of the three. The voice of the drake is a low blowing hiss; the female has a harsh quack, seldom heard. The male display consists of a rhythmic bobbing forward and backward of the head, with the crest spread, the neck extended, the wings slightly lifted, and the long tail vibrating. The female answers in a similar but less marked way. The White-winged Duck (C. scutulata) has very similar display and habits. The voice is said to be loud in both sexes, but we never heard ours emit any sound other than weak grunts. Both this species and the Muscovy have conspicuous white wing coverts. The West African Hartlaub's Duck (C. hartlaubi) is smaller, but seems to have the same general habits. The loud quacking reported of the species is probably that of the female. We have not made an adequate study of this species in life. In proportions and color pattern, it is very close to the Muscovy and White-winged Ducks. Its upper wing coverts are blue-gray instead of white. 30 THE WILSON BULLETIN March 1945 Vol. 57, No. 1 The anomalous Brazilian Teal (Amazonetta ["Anas"] brasiliensis) probably earns its logical place with the Cairinini, for it seems to be a dwarf Cairina, resembling that genus in general shape and propor- tions, and even in habits. Like them, it is a tropical forest bird. The display of the male is so simple as to consist merely in a lifting of the neck, as he whistles loudly. The female quacks briefly and moves her head up and down, slightly sidewise. Male and female differ in plumage and in the color of the bill, but both are rather bright, and there is no eclipse plumage. The downy young looks like a miniature young Muscovy. The three genera Chenonetta, Aix, and Nettapus have a smaller, smoother, and less flat bill, recalling those of 2Branta and of Chlophaga, but this is of no special taxonomic importance. Chenonetta has long legs and looks like a small goose; Aix has rather short legs like those in Cairina, while Nettapus has legs so short that the birds are almost unable to walk. Because of the great similarity of the females, it seems entirely unnecessary to separate generically the Mandarin and the Carolina Wood Duck, and we combine them in the genus Aix. As we have explained above, both these birds have the body proportions, voice, and habits of the tribe, and they are far from all the river ducks. A curious fact to be recorded is the inability of these two allied species to produce hybrids, although when associated in captivity they pair freely. There is a slight but not important difference in the voice and display of the two birds. The Mandarin drake has the more com- plicated posture: he lifts his wing fans and crest and blows up his chest, slowly lowers his head until his bill touches the water, then jerks his head back quickly with a short, subdued, snorting whistle, uib. Several drakes perform together with many short flights and perchings. The female answers with movements of her neck and head. In the Wood Duck, the male just raises his crest, arches his neck, and bows, with softer and more frequently repeated whistles, jiib, jiib. He never displays in company with other males. The female behaves much like the Mandarin, but she calls more often and has a softer, more melodious voice. Both Mandarin and Wood Duck form strongly attached pairs (Heinroth, 1910). The downy young of Aix galericulata resembles that of Cairina, but is paler and duller and has an additional dark stripe below the eye, as in Chenonetta. It is very difficult to assign a place to the small Australian species, Chenonettajubata, usually known as the Maned Goose, but also called locally the Wood Duck. It has a certain superficial resemblance to the species of Chlophaga, but is smaller and differs widely from them in its habits, behavior, and display. Furthermore, the downy young is brown and yellowish and has almost the same shape and color pattern as the young Mandarin Duck, including the dark parallel J. l)elacour THE FAMILY ANATIDAE 31 Ernst Mayr face lines. Ths seems to indicate its real affinity. The pattern is totally different from the bold grayish- or blackish-brown and white pattern which is so characteristic of the young in Chtophaga and allied genera. Like the other members of the present tribe, the Maned Goose is a tree-perching, hole-nesting bird. The voice of the male is a low, whizzing whistle, that of the female a soft quack, drawn out with a special modulation like a mew. The display of the male is simple, consisting in raising the head and neck, as he calls and puffs out his mane; that of the female is Arias-like, a sidewise movement of the head with neck extended, as in the Mandarin and Carolina Wood Ducks. The females sometimes engage in "incitement displays," like certain river ducks and sheldrakes. Chenonetta has a short, smooth bill, much like that of Chlophaga and Branta, but also similar to that of the genus Nettapus, and not very different from those of the Mandarin and Carolina Wood Ducks. Its legs are rather long, like those of Sarkidiornis, but much more slender, and it walks easily and daintily. It is very gentle in temperament. The pygmy geese (Nettapus) are the smallest members of the family, and also some of the most beautiful. They have small Branta- like bills and such extremely short legs that they can hardly progress on land. They perch freely, fly and swim well. All three species are tropical. They have much white and green in the plumage, and the sexes are slightly but clearly different. One species (N. 1/2oromandelianus) has a well-marked breeding plumage in the male. The downy young of the pygmy geese are of the usual shape for the tribe, but have peculiar dark gray and white patterns. As in the genus Aix, the downy young vary from species to species. The African Pygmy Goose (Nettapus auritus) has a thick bill. In both sexes the display is much like that of the Wood Duck, as we have often observed in the wild in Madagascar and in captivity at Cl[res. Its voice is a soft whistle in the male, a weak quack in the female. The Green Pygmy Goose (N. pulchellus), of Australia, is little known, but seems to be similar in voice and display to the African species. The Indian Pygmy Goose, or "Cotton Teal" (N. 1/2oromandelianus), whose range extends from India to Australia, has a flatter bill, is still smaller, and has several peculiarities, notably a breeding plumage which the male assumes for only a few months. The male's voice is a curious rattling cackle, and both sexes have a quick "nervous" jerking of the neck. The display of the male is elaborate, consisting of an arching of the neck, with a partial opening of the wings, showing the white patches on the primaries. March 1945 32 THE WILSON BULLETIN Vol. s7, No.  5. TRIBE MERGINI. SEA DUCKS The various tribes of diving ducks are completely different in pro- portions, pattern, and habits. The sea ducks show no close relation- ship with the pochards or the stiff-tailed ducks. Their lobed hallux, a functional adaptation, is of little phylogenetic significance. Delacour (1936:376), as well as Heinroth and other authors, has pointed out the obvious relationship of the mergansers (Mergus) with the golden-eyes (Bucephala); and in spite of the wide difference be- tween the extreme forms of the tribe (Mergus and Somateria), the sea ducks form one of the most closely knit subdivisions of the anatine subfamily. The seven genera are connected with one another by intermediate species. The Hooded Merganser (Mergus cucullatus), for example, connects the larger mergansers, through the Smew ("Mergellus" albellus) and the Buffle-head (Bucephala albeola) to the golden-eyes. The Harlequin (Histrionicus) is a link between the Old-squaw (Clangula) and the scoters (Melanitta), as is the Labrador Duck (Camptorhynchus) between the Old-squaw and the eiders (Somateria). On the other hand, the golden-eyes, the Old-squaw, and the Harlequin are undoubtedly related, as is proved by the same bold pattern of dark gray and white of all their downy young. The downy young of the White-winged Scoter (Melanitta fusca) is also very similar and thus connects the whole group to the other species of the genus (M. perspicillata and "Oidemia" nigra). In turn, the downy young of the last two species link them to the eiders, all being brown above, white underneath, without strong markings. Also, immature Surf (perspicillata) and White-winged Scoters closely resemble im- mature Harlequins in their general color as well as in their white head markings, which are already suggested by the white patch on the sides of the head in the Buffie-head. The ducks of the tribe Mergini are rather isolated, but, in our opinion, they are closer to the Cairinini than to any others. The nesting habits of the mergansers and the golden-eyes, their long and broad tails and their general behavior are suggestive of a certain affinity between the two tribes, which is corroborated by the attraction that such birds as the Mandarin and Wood Ducks exert on golden- eyes and Harlequins when they are associated on a lake. The birds of this tribe, with a very few exceptions, spend a part of their time at sea, and animal life constitutes their principal food. They all are great divers. Their bill is strong, with a large hooked nail, and varies from long, thin, and narrow to thick and short, according to their principal food (fish, mussels, etc.). Their wings are short and their flight heavy, and they walk with some difficulty, the eiders being less clumsy on land than the others. The majority of the species nest in the hollows of trees, in holes and crevices in rocks, or any other sort of deep shelter. Some of the I. Delacour THE FAMILY ANATIDAE 33 Ernst Mayr scoters and eiders, however, deposit their eggs on the ground in the open, among grass and bushes. All male Mergini are brightly colored and have a distinct eclipse plumage, the scoters, which are prevailingly black, and the two dull- colored southern mergansers being exceptions. They are not adult before their second or third year. In some cases, the females show a definite change in colors according to the season. There is no metallic color in the beautiful plumage of the drakes, not even in the speculum. Iridescent gloss occurs only on the head of the golden-eyes and mergansers and on the speculum of Steller's Eiders. Sea ducks are very silent birds as a rule, even the females; female eiders, however, utter frequently a harsh grunting cackle. Some of the others utter a similar cackle during the breeding season; at that time, the males emit low, subdued, ventriloquial grunts or whistles, differing from species to species. The only noisy drake is the Old- squaw, which calls loudly in all seasons. The sea ducks generally have very elaborate displays which have little resemblance to those of any other Anatinae, except perhaps to some of the postures of the stiff-tailed ducks. All sea ducks live in the cold or temperate parts of the northern hemisphere, with the curious exception of two rare southern mergansers inhabiting Brazil (octosetaceus) and the Auckland Islands, south of New Zealand (australis). The four species of eiders ("Polysticta" stelleri, "Arctonetta"fischeri, Somateria spectabilis, and S. mollissima), although closely related to one another, stand somewhat apart from the other sea ducks. The syrinx has a structure like that in the river ducks, and the downy you.rig lack the black cap typical of most sea ducks. We reject the peculiarity of the bill of Steller's Eider (S. stelleri) as a valid generic criterion. The four species agree closely in color pattern, and in the nature of their feathers, notably in the velvety-green and grayish-blue ones of the head and the long, curved ornamental secondaries. The peculiar green pigment on the head of the male is a unique feature of this genus. The females of the four species are much alike. All eiders are ground nesters and breed usually near the sea- shore, but also on the arctic tundra, near fresh-water pools. The Old-squaws, Harlequins, scoters, and eiders resemble the mergansers and golden-eyes in voice as well as in display, though the display is simpler, consisting of stretching the neck and calling, with an up- ward jerk of the bill. The extinct Labrador Duck (Camptorhynchus) seems to be about halfway between the eiders and the Old-squaw. The male is colored more like an eider, the female more like a scoter or Old-squaw. The three scoters (Melanitta, including "Oidemia") form a very compact group, and it would be misleading to divide the group into several genera merely because each of the three species has certain structural peculiarities (Miller, 1926). The Common Scoter (M. March 1945 34 THE WILSON BULLETIN Vo. $7, .,,to.  nigra) has an even more strongly emarginate first primary than the male golden-eye. It has about the simplest syrinx, with no bulla and no enlargement of the trachea. The White-winged Scorer (M. fusca) and Surf Scorer (M. perspicillata) have a big, bulb-like inflation of the trachea. The genera Clangula (Old-squaw) and Histrionicus (Harlequin) occupy a central position among the sea ducks. They lead to the scoters and eiders on one side and to the golden-eyes and mergansers on the other. Clangula is by far the more vocal of the two, but otherwise the displays of the two genera are very similar. It has been claimed repeatedly that the Old-squaw has two "eclipse" plumages, the first one acquired by partial molt, February-May; the second, also by partial molt, late July-August. However, as Sutton (1932, Auk, 49:42-51) has shown, two eclipse plumages are merely simulated by the protracted postnuptial molt. Both species are ground nesters, although the Harlequin is reported to nest occasionally in holes in trees or in cliffs. The golden-eyes (Bucephala) nest in holes in trees and are more partial to fresh water than the previously discussed genera of this tribe. The courtship displays of the males are very elaborate, but on the whole very much like those of the mergansers (see below). In fact, except for the shape of the bill, the golden-eyes are exceedingly close to Mergus. Female Common Golden-eyes (dangula) and Bar- row's Golden-eyes (islandica) resemble female mergansers closely in general color pattern; and their downy young are like those of the mergansers except that the black cap extends below the eye and the cheeks are pure white. Hybrids between Bucephala clangula on one side, and Mergus albellus (Sinew) and M. cucullatus (Hooded Mer- ganser) on the other side, have been found repeatedly in the wild state, indicating the close affinity of the golden-eyes and mergansers. The syrinx in the two genera, with large bullae, and the inflated bulbs of the trachea, are additional proof of this relationship. The Sinew lacks the enlargement of the trachea and has a smaller bulla. We have found no description of the syrinx of the Hooded Merganser or the Buffie-head. The mergansers (Mergus) are well characterized by their long, thin saw-bill. Nothing is known of the nesting of the three rarer species (squamatus, australis, octosetaceus). The Red-breasted Mer- ganser (serratot) nests on the ground among rocks and in depressions. The other three species (albellus, cucullatus, and merganser) nest by preference in tree holes. The display varies with each species, but consists generally of the following main features: (1) sudden rapid stretching of head and neck upwards, bill gaping, and quick return to normal position; (2) rising on water, beak touching breast; (3) spasmodic movement of feet, throwing up a spurt of water behind. The whole display is associated with a raising of the crest, bowing, . Delacour THE FAMILY ANATIDAE 35 rnst Mayr splashing, and chasing. Females have a simpler display, reproducing some of the male's postures in a rudimentary way. The downy young are dark brown above, white below, with a bold pattern resembling that of the golden-eyes, but they have a rusty tinge on the sides of the head, except in the Smew. Unlike all other ducks, mergansers are adapted to the chase of moving prey. Their body is more streamlined than that of their nearest relatives, the golden-eyes. This difference in form is particu- larly apparent in the sternum. In this connection also, the Smew and the Hooded Merganser seem to be somewhat intermediate be- tween the more typical mergansers and the golden-eyes. We cannot see any good reason for a generic division of the merganser group. 6. TIBE OXYURINI. STIFF-TAILED DUCKS This curious tribe of diving ducks has no apparent close con- nection with any other. Their rectrices are long and stiff, and their tail coverts are very short. The nail of their broad and depressed bill is hooked and sharp. Their legs are placed so far back on the body that they can walk only with difficulty. The neck is short and very thick. In the northern species, the postnuptial molt produces a dull plumage that is replaced in the spring by a bright prenuptial plumage. The downy young have a peculiar pattern. Stiff-tailed ducks are almost voiceless in ordinary times, but the drakes, during their court- ship, emit a variety of squeaking and clucking noises. Their display is striking: they lift their tails, and puff out their chests; then, stretch- ing their necks forward and backward, they slap their bills on their inflated chests. They also press their bills on their lifted and puffed chests, with the tail down in the water, and finally with both feet they kick water, which spurts backwards. The females stretch out their necks with their bills open. They lay the largest of all known duck eggs. They build large and elaborate nests among reeds and rushes. The male assists his mate in the care of the young. With their small wings, these ducks have a labored flight, but they are marvelous divers. They feed mostly on vegetable material, although they like animal food as well. The North American Ruddy Duck (Oxyura jamaicensis) is mi- gratory, as is the larger and duller White-headed Duck (0. leucocephala) which lives around the Mediterranean Sea and in Central Asia. The small Masked Duck (dominica) from the West Indies and troPi- cal America is undoubtedly congeneric; no valit character has ever been pointed out to support the genus Noraonyx that was proposed for this species. The tropical forms from South America (ferruginea, vittata), Africa (maccoa), and Australia (australis) are so similar in every respect that they must be listed as subspecies of 0. australis. We believe that the ranges of ferruginea and vittata do not overlap during the breeding season. March 1945 36 THE WILSON BULLETIN Vo. 57, o. i The weird Australian Musk Duck (Biziura lobata) is certainly a member of this group, in spite of its thick bill and carnivorous habits. Its display is like that of typical members of the group. The African White-backed Duck (Thalassornis), also found in Madagascar, appears very different, but its plumage pattern recalls that of the female Masked Duck. In color pattern, the downy young are somewhat different from those of Oxyura but resemble them in shape and structure of the tail. Delacour has observed the species at length, in the wild and in captivity. They are strange little birds, always found in pairs or families, quarrelsome, very sedentary and inactive. We seldom saw one fly, but they dive with great ease. They cannot walk, and they swim slowly. They have no noticeable display, and the two sexes are alike in coloration. Their necks are comparatively long, and they often stretch them to full length. Their voice is a harsh whistle which recalls that of certain Dendrocygna. They further differ from Oxyura in their very short tails. Even more aberrant is the parasitic Black-headed Duck (ttetero- netta atricapilla) from South America. It differs from typical stiff- tailed ducks in that it lacks a lobe on the hind toe, and has a fairly soft, short tail and elongated upper tail coverts, smaller feet and a narrower bill. On the other hand, as Wetmore (1926:84) has pointed out, tteteronetta agrees with the Oxyurini "in the full, loose skin of the neck, development of special, distensible sacs about the head in the male, small wings, glossy, shining plumage, and lack of a bulla ossea." The color pattern is very much like that of females of Oxyura. They dive as well as members of the genus Oxyura do, and swim like them except that the tail is not held at an angle. The eggs are huge, relative to the size of the female, and the parasitic habits of this species are foreshadowed by the semiparasitic habits of other members of the Oxyurini (Friedmann, 1932). The downy young of ttetcronetta has apparently not yet been described. 7. TRIBE MERGANETTINI. TORRENT DUCKS The Andes are the'home of a very curious species of small duck with a narrow bill, a long, stiff tail, and sharp spurs at the bend of the wing. They live along rapid mountain streams, dive with con- siderable skill, perch on rocks, and nest in crevices. In the present state of our knowledge, it is difficult to assign them a place, but they are certainly not closely related to the mergansers, and may rather b aberrant relatives of the stiff-tailed ducks. The plumage of the adults (different in the two sexes but elaborate in both), and the pattern of the downy young, are striking and peculiar. The structure of the syrinx and the courtship habits are apparently unknown. The genus has been thoroughly revised by Conover (1943, Field Mus. Nat. Ilist. Zool. Ser., 24:345-356). It seems to us, however, that the geographical forms of Merganetta armata are not sufficiently dis- tinct to justify the recognition of three separate species. We follow Hellmayr, Hartert, and Peters in considering them conspecific.