The Wager Bay area in northeastern Keewatin was surveyed for nests of raptorial birds during late July and August in 1976 and 1977, and the southwestern part of Melville Peninsula was also surveyed in August 1977. These surveys established Wager Bay and Melville Peninsula as the most productive nesting areas known for the endangered Peregrine Falcon (Falco peregrinus tundrius). More Peregrine Falcon sites producing young were located at Wager Bay than are known to exist in any other area of the North American Arctic. The production of young Peregrine Falcons at Wager Bay in 1976 and 1977 exceeded that of any area surveyed during the 1975 North American Peregrine Falcon Survey. In 1976 we located 14 nest sites occupied by Peregrine Falcons, 5 sites occupied by Gyrfalcons (Falco rusticolus), 11 sites occupied by Roughlegged Hawks (Buteo lagopus), and 1 nest site of a Golden Eagle (Aquila chrysaetos). In 1977, 27 Peregrine Falcon sites, 5 Gyrfalcon sites, 2 Rough-legged Hawk sites, and 1 eagle site were located. In 1977, Peregrine Falcons reoccupied at least 54%, and possibly as many as 91%, of the nesting territories occupied in 1976. Of the 13 peregrine sites visited in 1976, 85% produced young; young/occupied site averaged 2.08, and young/successful nest averaged 2.45. In 1977, 84% of the 22 visited sites produced young; young/occupied site averaged 2.21, and young/successful nest averaged 2.95. The Peregrine Falcon sites did not differ significantly between years in percent successful sites, young/occupied site, or young/successful nest. There was no correlation between the number of young Peregrine Falcons produced at nest sites in 1976 and the number produced at the same sites in 1977. The nests that had been visited in 1976 produced 2.16 young/successful nest in 1977, as compared with 3.3 young/successful nest among the nests not previously visited. This difference was significant. Fifteen occupied Peregrine Falcon sites were located on Melville Peninsula, at least 10 of which produced young. The average number of young/successful nest was 2.6. The Peregrine Falcon populations at Wager Bay and Melville Peninsula did not differ significantly in either number of young/successful nest or in mean distance between occupied sites. Both the Wager Bay and the Melville Peninsula Peregrine Falcon populations are considered to be undepleted populations. A total of 30 Peregrine Falcon chicks from 11 nests were banded at Wager Bay and 6 chicks from 3 nests on Melville Peninsula. One of the banded birds was later captured on North Padre Island, Texas. Received 21 December 1978, accepted 11 May 1979.

Wildlife Service, Government of the Northwest Territories, Yellowknife, Northwest Territories XIA 2L9 Canada RECENT surveys of known nesting areas of the Peregrine Falcon (Falco peregrinus) in northern Canada and Alaska have shown that both occupancy of nest sites and productivity have declined in many areas (Fyfe et al. 1976). Several populations of the arctic peregrine had declined to such an extent that Newton (1976) commented, "the entire F. p. tundrius population is now well into decline." Unfortunately, little was known about the Peregrine Falcon populations of Kee- watin district in the Northwest Territories, especially in the northeastern areas. During July and August of 1976 we conducted a survey of nesting raptors at Wager Bay. This survey revealed a highly productive population of Peregrine Falcons. In 1977 the surveys were intensified at Wager Bay and expanded to include Melville Peninsula. SPENCE Walker Lake c,O-' -' MELVILLE ,,( PENINSULA Curtis Lake Baker Lak Fig. 1. Map of northeastern Keewatin showing the areas searched for raptor nests at Wager Bay and on Melville Peninsula. METHODS The study area.--The area searched for raptor nests around Wager Bay included the shorelines of Wager Bay, Brown Lake, Ford Lake, and the shores of adjacent rivers and lakes within 15-30 km of these water bodies (Fig. 1). On Melville Peninsula, we searched the southwestern section, concentrating mostly on river valleys and cliffs overlooking large lakes (Fig. 1). The coastal cliffs were not searched. Some areas of Melville Peninsula featured miles of almost continuous deep river gorges. Rocky hills and sea cliffs (elevations up to 580 m), rock outcrops, and cliffs along the rivers that occur throughout both study areas provide innumerable ledges suitable for nesting by raptors. The tundra habitats in both areas range from wet lowland areas dotted with lakes, ponds, and standing water to well-drained upland sites. Potential prey species include small mammals, passerine birds, and larger birds. Surey techniques.--Because the Wager Bay area had not previously been searched for raptors, we had no prior knowledge of nest sites or of suitable nesting habitat. Therefore, during the initial survey in 1976, we concentrated our searches along the shores of Wager Bay, Brown Lake, Ford Lake, and along lakes and rivers where 1:250,000 topographic maps showed cliffs or broken relief. We searched by flying close to cliffs and outcrops and looking for nests, flushed birds, or excrement stains on the rock. Most of the searching at Wager Bay was done from a Cessna 185, but from 8 to 10 August 1977 we 664 CA.Er AND HEARD [Auk, Vol. 96 searched with a Bell 206 helicopter, and on Melville Peninsula a Hughes 500 helicopter was used. When stains were observed on a cliff, we flew past the cliff several times to locate any nests. When a nest was observed, we attempted to count eggs or young. We also attempted to identify the species of all raptors observed. All sightings of possible nest sites and confirmed occupied nests were mapped. In 1977 we concentrated first on revisiting all occupied and potential nest sites located in 1976. When a site occupied by Peregrine Falcons in 1976 was found unoccupied in 1977, we searched the surrounding area looking for alternate sites. Thereafter, we expanded our searches to areas unsurveyed during 1976. The procedure used on Melville Peninsula was the same as that used at Wager Bay in 1976 because we had no prior knowledge of nest sites on Melville Peninsula. Surveys at Wager Bay were conducted from 23 July to 30 August in 1976 and 18 July to 28 August in 1977. Our survey of Melville Peninsula was conducted from 15 to 17 August 1977. Where possible, we later visited suspected nest sites on foot to confirm occupancy, to locate the nest and describe the site, to count numbers of eggs and young, to determine the developmental stage of the young, and to collect any addled eggs for analysis of egg shell thickness and pesticide residue. Eggs were sent to the Canadian Wildlife Service for analysis. Banding.--When possible, Peregrine Falcon nestlings were banded with a numbered metal band (size 7A) on one leg and a black plastic band with white numbering (using a code of two numbers and one letter) on the other leg. The young falcons were banded after they had reached the large downy stage, and most were partially feathered. RESULTS Number, location, and site characteristics of Peregrine Falcon eyries.--In 1976 we located 14 eyries occupied by Peregrine Falcons at Wager Bay and 27 occupied eyries in 1977. Ten of the occupied eyries in 1977 were at or near sites occupied in 1976, and 17 were previously unknown. Occupied sites averaged 8.0 km apart (range 3.2-19.3 km). Twenty-four of the nest cliffs were above or near lakes, streams, or the sea (Table 1). Nests averaged a distance of 5.8 km from the major water bodies of Wager Bay, Ford Lake, and Brown Lake. Eighteen nests were less than 4 km from these water bodies, and only 4 were more than 15 km from them. We located 15 occupied Peregrine Falcon nests on southern Melville Peninsula (Table 2). Twelve of these nests were on cliffs above lakes. The occupied sites averaged 9.2 km apart (range 4.8-12.9 km), if nests MP and MP, on the periphery of the study area are excluded. Of the peregrine nests observed on Melville Peninsula, 70% were on ledges with- out apparent nest material. The other 30% were in old stick nests of other species. At Wager Bay, 32% of the peregrine nests observed were in stick nests, and the remainder were on ledges without apparent nest material. Thus, the Wager Bay and Melville Peninsula populations are virtually identical in their use of nest types. Nesting success and productivity of Peregrine Falcons at Wager Bay.--Overall, the production of Peregrine Falcons during 1976 was remarkably similar to that during 1977. The percentage of successful nests of Peregrine Falcons (defined as those occupied eyries having living young at the time of our visit), number of young/ occupied site, and the number of young/successful nest did not differ significantly between 1976 and 1977 in the Wager Bay area (Table 3). Nest sites that we had visited in 1976, however, produced fewer young on the average in 1977 than did those sites that we first discovered in 1977 (Table 4). If sites Pa^., P,^, and P^ are excluded from the sample of nest sites visited in 1976, then there is a significantly (P < 0.025) higher number of young/successful nest at sites first discovered in 1977 than at those sites first visited in 1976. If sites Pa^, P,^, and Pn^ are included in the sample of sites visited in 1976, then the difference in young/successful nest is less, but still approaches significance (0.05 < P < 0.1). The TABLE 2. Site characteristics and productivity of Peregrine Falcon eyries on southern Melville Peninsula, 1977. Distance Number Number Nearest to nearest Site Site description Nest type of young of eggs site site (km) MP Cliff above small pond Grassy ledge 3 - MP5 30.2 MP2 Cliff above lake Grassy ledge 3 - MP4 12.9 MPa Cliff on river Ledge 3 a - MP4 11.3 MP4 Cliff on lake Grassy ledge 1 a 2 MP3 11.3 MP5 Cliff on lake Grassy ledge 2 - MP 30.2 MP6 Low cliff above small stream Undetermined ? ? MP, 8.8 MP7 Cliff on lake Undetermined ? ? MP6 8.8 MPs Cliff on lake Undetermined ? ? MPo 12.1 MP9 Cliff on lake On rock ledge 2 a - MPs 12.1 MPo Cliff on lake Stick nest 3 a - MP9 5.6 MPn Cliff on lake Stick nest 2 a - MPx0 4.8 MPx2 Cliff on lake Undetermined ? ? MPn 6.4 MPxa Cliff on lake Undetermined ? ? MPo 5.6 MPx4 Cliff on lake Grassy ledge 3 a - MP5 9.6 MP5 Cliff near lake and river stick nest 4 a - MPx4 9.6 Nest checked from helicopter only. difference in young/occupied site between the latter two samples was not significant, nor was the percentage of successful nests. Reoccupancy and productivity of previously occupied sites.--Of the 14 sites oc- cupied by Peregrine Falcons in 1976, at least seven were reoccupied in 1977 (Table 4). One nest (P4) was not checked, and another (Pt) was checked only from the air. Gyrfalcons occupied two of the 1976 peregrine eyries (Pn and P4). Three nests (P3A, PSA, and PnA) at locations close to sites occupied in 1976 could be considered alter- nates. These three alternate sites averaged 2.4 km from the site previously occupied. The average distance between apparent alternate sites is approximately 30% of the average distance between occupied sites and less than the minimum distance re- corded between any two simultaneously occupied sites, suggesting that retocation by these three pairs did occur. From these data we calculated a minimum and maximum reoccupancy rate for the Wager Bay population. The maximum reoccupancy rate possible was 91% (10 of 11 nests). In making this calculation, we assumed that sites P4, Pt, and P4 were TABLE 3. Comparison of reproductive success of Peregrine Falcons at Wager Bay, Northwest Territories in 1976 and 1977. Young + Young/ Occupied Percent Young/ eggs/ successful Year nests successful a occupied site occupied site nest 1976 14 85 2.08 2.31 2.45 (11/13) (27/13) (30/13) (27/11) 1977 27 84 2.21 2.42 2.94 (18/22) (53/24) (58/24) (53/18) Statistical comparison X a = 0.045 t = 0.254 t = 0.338 t = 1.22 between years df = 1 df = 35 df = 35 df = 27 P > 0.75 P > 0.5 P > 0.5 P > 0.1 a Reproductive success not determined for one nest in 1976 or for five nests in 1977. October 1979] Peregrine Falcon Reproductive Success 667 2' O . Fig. 2. Bay, 1976 and 1977. I 0 1 3 4 YOUNG PRODUCED IN 1976 Lack of correlation between number of young produced at 10 Peregrine Falcon sites at Wager not adequately checked and therefore that alternates to these sites might have been occupied although we did not locate them, and we assumed that sites P3A, PSA, and PA were alternates to sites Pa, Ps, and P, respectively. The minimum reoccu- pancy rate was calculated to be 54% (7 of 13 nests). In this calculation, only P4 (the unchecked site) was excluded from the sample, and we assumed that Pa, P,, Po, Ps, Pn, and P4 were unoccupied (i.e. we assumed that no alternates existed). Assuming that sites PaA, P*A, and PA are alternate sites, we can compare pro- ductivity at sites visited in both 1976 and 1977. In 1976, 85% (11/13) of all occupied sites checked produced young; in 1977, 80% (8 of 10) were successful. The number of young/occupied site averaged 2.08 (27/13) in 1976 and 2.0 (20/10) in 1977. The number of young/successful nest averaged 2.45 (27/11) in 1976 and 2.5 (20/8) in 1977. None of these differences between years was significant (Table 4). No significant correlation existed (r 2 = 0.032) between the number of young Pere- grine Falcons produced at a given site in 1976 and the number produced in 1977 at the same site (Fig. 2). Nesting success and productivity of Peregrine Falcons on Melville Peninsula.- Of the 15 occupied sites that we located on Melville Peninsula, 10 were known to have produced young in 1977. As all the sites were visited in mid-August when young might have already left the nest, however, and as several of the sites were checked only by helicopter, it is likely that some of the remaining five nests also produced young that we did not observe. The 10 known successful sites produced 26 young, an average of 2.6/successful nest (Table 2). The Wager Bay and Melville Peninsula Peregrine Falcon populations are similar in both site spacing and in productivity. The distance between nests did not differ significantly between the populations (t = 0.725, df = 38, P > 0.4), nor did the number of young/successful nest (t = 0.884, df = 26, P > 0.2). The percentage of successful nests on Melville Peninsula appeared lower than at Wager Bay (66% vs. 84%). This is probably because sites on Melville Peninsula were visited later in the season and also were not checked as intensively as the sites at Wager Bay. Overall, the population characteristics of Peregrine Falcons nesting on Melville Peninsula and at Wager Bay appeared similar. Observations of nest sites of other raptor species.--In 1976 we located 11 nest sites occupied by Rough-legged Hawks, 5 sites occupied by Gyrfalcons, and 1 site oc- cupied by a pair of Golden Eagles. In 1977, we located five occupied Gyrfalcon sites at Wager Bay. At one nest site, two young were observed and banded; at another, two fully fledged young were observed. Two of the Gyrfalcon sites had been occupied by Peregrine Falcons in 1976. On Melville Peninsula we located one Gyrfalcon site. At Wager Bay we located only two Rough-legged Hawk nest sites in 1977, as compared with 11 sites in 1976. Neither of these sites successfully fledged young, although 1 nest initially had 2 eggs and the other 2 young. Seven occupied Rough- legged Hawk nests were located on Melville Peninsula. These nests produced an average of 2.3 young/nest, as compared with 3.0 young/successful nest among 6 Rough-legged Hawk nests visited at Wager Bay in 1976. Our surveys were conducted at the optimal time for locating successful Peregrine Falcon and Rough-legged Hawk sites. Young of both species were present in the nests but had not yet fledged. The parents had been using perches for several weeks so excrement stains were highly visible. Conversely, young Gyrfalcons were fledged and flying at the time of our surveys and therefore likely to be away from the nest sites. Thus, our survey was probably less successful in locating Gyrfalcon sites than it would have been if conducted a month earlier. Nests of all raptor species at Wager Bay and Melville Peninsula were located on cliffs or rock outcrops; none was on soil cutbanks. Rough-legged Hawks nested throughout the area, using rock outcrops away from bodies of water as well as cliffs on the sea, lakes, and streams. No Gyrfalcon nests were on sea cliffs. Rough-legged Hawks often used lower, less protected cliffs than did Peregrine Falcons. Most of the nests of all species, however, were on or near broad ledges, and the majority were accessible without a rope. Banding and band recoveries.--Thirty Peregrine Falcon chicks from 11 nests were banded at Wager Bay, and 6 were banded from 3 nests on Melville Peninsula. One of the falcons banded on Melville Peninsula was live captured and released on North Padre Island, Texas on 17 October 1977 (H. Armbruster, Canadian Wildlife Service, pers. comm.). DISCUSSION Productivity of Peregrine Falcons in northeastern Keewatin and Melville Pen- insula.--The raptor studies conducted during 1976 and 1977 established Wager Bay and Melville Peninsula as the most productive nesting areas known for the rare and endangered tundra Peregrine Falcon. More producing peregrine falcon eyries are now known at Wager Bay than in any other area in the North American Arctic TABLE 5. Occupancy and productivity of Peregrine Falcons in arctic North America. Total known Number young Number of Area a sites Occupiedl975 produced sites producing West Greenland 9 8 12 5 Ungava Coast 27 11 16 9 East Coast 5 0 0 0 Interior Barrens 16 1 3 1 Central Arctic Coast (NWT) 27 13 21 11 Horton River 15 5 9 3 Banks Island 14 7 18 6 North Slope (YT) 12 5 - ? Northeast Alaska 28 3 - 2 + Colville River 46 12 - ? TOTALS (1975) 199 65 79+ 37+ Wager Bay (1976) 14 14 27+ 11+ Wager Bay (1977) 31 27 53+ 18+ Melville Peninsula (1977) 15 15 26+ 10+ TOTALS (1977) 46 42 79+ 28+ a Data from Fyfe et al. (1976). (Table 5). The nests we visited at Wager Bay and Melville Peninsula produced as many young in 1977 as did all the Peregrine Falcon nests in the North American Arctic visited during the 1975 survey (Table 5). Moreover, large areas of north- eastern Keewatin and Melville Peninsula have a combination of ideal nest sites (cliffs and outcrops near many lakes, ponds, and streams) and abundant passerine birds for prey, which makes these areas highly suitable for nesting Peregrine Falcons. We suspect that more nests remain to be discovered at Wager Bay and that the 15 sites located on Melville Peninsula represent only a small fraction of the nest sites there and on the Rae Isthmus. The entire area of northeastern Keewatin probably pro- duces several hundred Peregrine Falcons each year. For example, Alliston and Pat- terson (1978) recently located 41 previously unknown eyries of Peregrine Falcons on Boothia Peninsula and Sumerset Island. Fyfe (1969) considered Wager Bay and Melville Peninsula to be areas of "limited nesting" habitat (approximate breeding density of 1 pair/259 km2. We calculate the breeding density at Wager Bay and Melville Peninsula at approximately 1 pair/50 km 2 (assuming that the area occupied by a pair equals the area of a circle of radius " the inter-nest distance). Fyfe considered a density of 1 pair/52 km 2 as "optimum nesting" habitat. Thus we must reclassify Wager Bay and Melville Peninsula as "optimum nesting" habitat, according to Fyfe's (1969) terminology. Reproductive and population status of Peregrine Falcons at Wager Bay and Mel- ville Peninsula.--The reproductive status of the Wager Bay and Melville Peninsula Peregrine Falcon populations cannot be assessed with certainty from our surveys, because we have no observations during the period of territory establishment or incubation. Pairs that fail to lay eggs or to hatch them successfully may abandon their eyries before July and August (Cade 1960), the period during which our surveys were conducted. If our surveys failed to detect such pairs, which nested but did not successfully hatch young, then our estimates of population density and site reoccu- pancy would be low, and our estimate of reproductive success rate for the overall population high. Of the 6 unsuccessful nests that we visited, 2 had unhatched eggs, 2 had dead young or evidence of young (e.g. white down feathers), and 2 had no sign of eggs or young. These findings suggest that our surveys were more likely to find successful nests or those in which young were hatched than to find nests which failed early in the reproductive cycle. However, we believe that the number of unsuccessful nests missed is unlikely to be large, because the nest spacing was quite uniform and the nest density we observed was as high as has ever been reported for arctic Peregrine Falcons (Cade 1960, Fyfe 1969). Many populations of arctic Peregrine Falcons appear to have declined in recent years (Fyfe et al. 1976). Unfortunately, there are no previous surveys with which to compare our findings at Wager Bay and Melville Peninsula. Thus, we have no direct evidence on the trend of these populations. If the Wager Bay and Melville Peninsula populations had declined significantly prior to our study, then previously these areas must have had nesting densities higher than in any other area of the Arctic previously studied. Only further surveys, preferably conducted during the entire nesting period, will confirm the trend of these populations. Occupancy rates of Peregrine Falcons.--The problem of determining occupancy rates in Peregrine Falcon populations stems from the difficulty in differentiating between the use of alternate sites within a breeding territory and actual loss of a pair from a nesting territory. Fyfe et al. (1976) state that "... alternate nest sites, though most frequently found on the same cliff, in some instances have been re- corded as far as 1.6 km from a previously used scrape." Without individually rec- ognizable birds, the distinction between a new pair and a previously known pair using an alternate nest site is impossible to make with certainty. We believe that sites Pa^, Ps^, and Pt^ should be considered alternates to sites P., Ps, and which were occupied by peregrines in 1976 but not in 1977 (Table 1). We feel that these sites are alternates because they are closer to the previously occupied sites than the minimum distance that we have observed between simultaneously occupied sites. Similarly, we cannot consider that the pairs of Peregrine Falcons that occupied sites P and P4 in 1976 were lost to the population in 1977 simply because Gyrfalcons usurped their nest sites; these displaced peregrines probably nested elsewhere. Ac- cording to Beebe (1977), replacement of peregrines at nest sites by Gyrfalcons, which arrive and set up territories earlier than peregrines, is natural and common. Only site Ps is considered to have actually been abandoned. Thus, we feel that the max- imum re-occupancy rate (91%) calculated for 1977 is likely closer to the true situation for the Wager Bay population than is the minimum value (54%). If the occupancy rate were 90%, it represents a much higher rate than that cur- rently seen in other populations in the Canadian Arctic (Table 6). Because all the known peregrine sites at Wager Bay were discovered in either 1976 or 1977, how- ever, occupancy rates there are perhaps not directly comparable to other areas where declines in occupancy rate have been measured over longer time spans. Changes in productivity in Peregrine Falcon populations.--The productivity rate of the northeastern Keewatin peregrines was remarkably similar between years (Table 3) and between areas. The productivity/successful pair was higher than that observed in many areas of the Arctic in 1975 (Table 7) and was near the maximum that could be expected for the species (Hickey 1969). Two aspects deserve additional comment. First, the lack of correlation in pro- ductivity between years at individual nest sites (Fig. 2) suggests that pesticide pol- lution is not the major factor affecting reproductive success. If pesticides must reach a threshold level before metabolism or behavior is altered enough to affect produc- tivity, then one would expect some pairs to consistently produce well, while others would consistently produce poorly. Fyfe (pers. comm.) believes that this is why some TABLE 6. Comparison of site occupancy by Peregrine Falcons at Wager Bay with other areas in the Canadian Arctic. a Area Sites checked Sites occupied Percent occupancy Ungava Bay 25 9 44 TheIon River 13 1 8 Central Arctic Coast (NWT) 27 12 48 Horton River 15 5 33 North Slope (YT) 11 4 36 TOTAL 91 31 34 Wager Bay maximum b 11 10 91 Wager Bay minimum b 13 7 54 Data from Fyfe et al. (1976). See text for explanation. pairs keep producing normally while the overall productivity and occupancy of a population is declining. This was not observed at Wager Bay. Such an analysis assumes that pairs are occupying the same nest sites each year. Reoccupancy by the same pairs cannot be determined with certainty without individually recognizable birds. Second, the observation that sites visited in 1976 produced significantly less in 1977 than did previously unvisited sites (Table 3) raises the distressing possibility that disturbance may produce delayed effects. We hope that this observation was due to chance, but future studies should address delayed effects. Grier (1969) de- tected no delayed effects on productivity of Bald Eagles (Haliaeetus leucocephalus) resulting from his having visited the nests. Platt (1977) presented evidence of delayed effects of disturbance on nesting in Gyrfalcons. Sites disturbed in one year appeared to be abandoned the following year. Productivity of other raptors.--Gyrfalcons apparently occupied sites at about the same rate in 1976 and 1977. Our studies were conducted too late in the summer to determine the productivity of the Gyrfalcons. At Wager Bay, Rough-legged Hawks had a much lower occupancy rate in 1977 than in 1976 and, as far as we know, did not successfully produce young in 1977. Reproduction by Rough-legged Hawks var- ies from year to year, because their prey (microtine rodents) are cyclic. We had TABLE 7. Comparison of productivity in arctic Peregrine Falcon populations. Pair with Young/suc- Area Year young Young/pair cessful pair Western Greenland 1972 7 2.30 2.60 1973 9 2.60 2.70 1974 5 3.00 3.00 1975 5 2.00 2.40 Ungava Bay 1970 7 1.30 1.71 1975 9 1.78 1.78 Thelon River 1970 3 2.00 2.67 1975 1 3.00 3.00 Central Arctic Coast (NWT) 1975 11 1.75 1.91 Banks Island 1975 6 3.00 3.00 Horton River 1973 2 0.60 1.33 1975 3 1.80 3.00 Wager Bay 1976 11 2.08 2.45 1977 18 2.21 2.94 Melville Peninsula 1977 10 2.60 2.60 thought that Rough-legged Hawks at Wager Bay might be less variable in their rate of reproduction than populations in some other areas because arctic ground squirrels (Citellus undulatus) were abundant in the Wager Bay area and available as alternate prey. Although ground squirrels were brought to the nest by Rough-legged Hawks later in the season, however, these alone were apparently not sufficient to allow successful raising of young. Perhaps only juvenile squirrels, which emerge later, are vulnerable to attack by Rough-legged Hawks. It is noteworthy that Rough-legged Hawks on Melville Peninsula produced young in 1977 while those at Wager Bay did not. Thus reproductive failures were apparently not synchronous over these very large geographical areas. RECOMMENDED FUTURE STUDIES The existence of more producing Peregrine Falcon pairs in the Wager Bay-Melville Peninsula than at any other known area in the Arctic makes the area ideal for long- term field studies of an apparently healthy population of arctic Peregrine Falcons. Long-term studies would be valuable in answering the following questions: 1. What is the degree of fidelity of male and female falcons to each other and to particular nesting territories? 2. Over how wide an area do young falcons produced in a given area disperse when establishing territories in following seasons? 3. Where do Peregrine Falcons from northeastern Keewatin winter, and by what routes do they migrate to and from these areas? 4. What levels of contaminants are being carried by Peregrine Falcons and their prey, and how do these affect reproduction and behavior? 5. What is the effect of human disturbance on falcon populations? The answers to most of these questions require continuous monitoring of the pop- ulation and its reproduction for several years, and the gradual accumulation of a substantial proportion of individually recognizable, marked birds in the population. From large numbers of visibly marked individuals, statistical information on pair fidelity, fidelity to nest sites, dispersal patterns of young, location of wintering areas, and migration routes could be collected. Continuous monitoring of the population would make it clear if some pairs consistently experienced reproductive failure, and if eggs of such pairs contain high levels of chemical contaminants. If high levels of contaminants were confirmed in the population, perhaps these could be correlated with the use of particular prey species or particular wintering areas. Finally, the Wager Bay-Melville Peninsula population is the only one in North America large enough to allow controlled studies of the effect of disturbance on Peregrine Falcons. Such studies are desirable in order to anticipate disturbance problems should the current proposal to make Wager Bay a National Park be carried out. ACKNOWLEDGMENTS This work was supported by the Environment-Social Program (Arctic Island Pipeline Project) of the Department of Indian Affairs and Northern Development Canada, and by Parks Canada. We thank M. L. Broderick, J. Burnford, J. Donaldson, and S. Stephansson for assistance in the field. Mark Crossman contributed many hours of safe and skillful flying without which the surveys could not have succeeded. R. Fyfe and S. Stephansson of the Canadian Wildlife Service offered valuable suggestions regarding field work and provided the bands used. U. Banasch, I. McT. Cowan, R. Fyfe, S. Johnson, D. Mossop, R. W. Nelson, and S. Stephansson read the manuscript and made many helpful suggestions. LITERATURE CITED ALLISTON, W. G., & L. A. PATTERSON. 1978. A preliminary study of Peregrine Falcon populations in the Polar Gas area, Districts of Franklin and Keewatin, N.W.T. Toronto, LGL Environmental Associates. BEEBE, F. L. 1977. Field studies of the Falconiformes of British Columbia. Vultures, hawks, falcons, eagles. Victoria, Occ. Pap., B.C. Prov. Mus., No. 17. CADE, J. T. 1960. Ecology of the Peregrine Falcon and Gyrfalcon population in Alaska. Univ. California Publ. Zool. 63: 151-290. FYFE, R. W. 1969. The Peregrine Falcon in northern Canada. Pp. 101-114 in Peregrine Falcon pop- ulations, their biology and decline (J. J. Hickey, Ed.). Madison, Wisconsin, Univ. Wisconsin Press. -- S. A. TEMPLE, & T. J. CADE. 1976. The 1975 North American Peregrine Falcon survey. Can. Fi'eld-Naturalist 90: 228-273. GRIER, J. W. 1969. Bald Eagle behaviour and productivity responses to climbing to nests. J. Wildl. Mgmt. 33: 961-966. HICKEY, J. J., ED. 1969. Peregrine Falcon populations: their biology and decline. Madison, Univ. Wisconsin Press. NEWTON, I. 1976. Raptor research and conservation during the last five years. Can. Field-Naturalist 90: 225-227. PLATT, J. B. 1977. A study of wintering and nesting Gyrfalcons on the Yukon North Slope during 1975 with emphasis on their behaviour during experimental overflights by helicopters. Ch. I. in Orni- thological studies conducted in the area of the proposed gas pipeline route: Northern Alberta, North- west Terrritories, Yukon Territory and Alaska, 1975. Arctic Gas Biol. Rept. Ser. Vol. 35.