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The literature review and fieldwork carried out by Zoltai et al. (1980) suggested that 39 avian species occur in the Aulavik National Park area. As a result of our eight weeks of fieldwork, we added only four new avian species to the park's list: tundra swan (Cygnus columbianus), red-necked phalarope (Phalaropus lobatus), western sandpiper (Calidris mauri), and purple sandpiper (Calidris maritima). Zoltai et al. (1980) reported gyrfalcons (Falco rusticolus) and Thayer's gulls (Larus thayeri) occurring in the park area, but these two species were not recorded in our study. Thus in total, 43 bird species have been recorded in Aulavik National Park, 41 of which were observed during this study (see Table 1). Amundsen Gulf, which separates Banks Island from the mainland, appears to be an effective geographic barrier to migrating birds. As a result, the avifauna of Banks Island is impoverished when compared to the mainland. For example, Ivvavik National Park in the northern Yukon Territory has recorded 143 avian species (Holcroft Weerstra, 1997) as compared to 70 bird species recorded for Banks Island as a whole or 43 species recorded for Aulavik National Park (Henry and Mico, 1997). Daily checklists were compiled while fieldwork was being carried out in ten different areas in the park, and Table 1 categorizes these species according to three relative abundance classes: common (recorded on 50 percent or more of the daily checklists), uncommon (recorded on between 49 and 20 percent of the daily checklists) or rare (recorded on less than 20 percent of the daily checklists). Table 1 shows that approximately 15 percent of the bird species (6 out of 41 species) were commonly observed, 29 percent of the species (12 out of 41) were uncommonly observed, and 56 percent (23 out of 41) were rarely observed in these areas of the park. Patterns observed during the two summers of this project were relatively consistent with 38 bird species being observed during the 1995 field season and 35 bird species being observed during the 1996 field season. Bird species observed only during the 1995 field season included the red-throated loon (Gavia stellata), tundra swan, Sabine's gull (Xema sabini), sanderling (Calidris alba), western sandpiper and American pipit (Anthus rubescens). Bird species observed only during the 1996 field season included the semipalmated plover (Charadius semipalmatus), red-necked phalarope and least sandpiper (Calidris minutilla). |
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As a result of their literature review and fieldwork, Zoltai et al. (1980) established 11 breeding records for bird species in the area of the park (see Table 1). Zoltai et al. (1980) did not explicitly state what evidence they required to establish a breeding record. Thus their breeding records may be based on sightings of nests with eggs or offspring or an adult bird with flightless young (as required by this study) as well as territorial behaviour, females showing the broken wing behaviour or other signs of bird species breeding in the park area. Using the former criteria, this study documented 21 new breeding records for Aulavik National Park (see Table 1). Breeding records from this study result in an extension of the breeding distribution maps as given by Godfrey (1986) for the following species: semipalmated sandpiper (Calidris pusilla), purple sandpiper, and buff-breasted sandpiper (Tryngites subruficollis). Nests of peregrine falcons, arctic race, (Falco peregrinus tundrius) containing flightless offspring were observed at two separate locations on cliffs adjacent to a river and a stream within the park. Due to the vulnerable status of peregrine falcons (COSEWIC, 1999), active nest sites should be disturbed as little as possible. If disturbance is suspected to cause any breeding failures among the peregrine falcons nesting in the park, special protective management actions should be considered as part of the zoning system for the park. Cliff nesting sites for peregrines, gyrfalcons and rough-legged hawks appear to be rare in Aulavik National Park and may be a limiting factor for these populations. This hypothesis should be the focus of future research; and, if substantiated, cliff nesting sites for these raptors may merit special protection. This study combined with Zoltai et al. (1980) documents that, of the 43 bird species known to occur in Aulavik National Park, 32 of them (75 percent) are now known to breed in the park. This pattern underscores the importance of Aulavik National Park as a fully protected area where diversity of tundra-adapted birds breed and raise their young. |
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Relative Abundance of Common Bird Species Daily checklists gave a coarse indication of the relative abundance of bird species (Table 1). The point count method (Ralph et al., 1995) is a more quantitative technique. It was used to estimate the relative abundance and examine the habitat association patterns for common bird species on three study areas within the park: the Eames River area (centered at 74°06.214'N and 120°45.077'W), the Muskox River area (centered at 73°45.677'N and 120°34.849'W) and the central portion of the Thomsen River area (centered at 73°13.849'N and 119°32.422'W). Thirteen avian species satisfied the arbitrary cut-off point (see Methods) and were included in this analysis. There are significant differences among the relative abundances of these bird species (Friedman's ANOVA, P < 0.05). Figure 2 summarizes these relationships. Lapland longspurs (Calcarius lapponicus) are clearly the most abundant bird species found on these three study areas. Its relative abundance is at least three to five times higher than the next most common bird species, black-bellied plover (Pluvialis squatarola). In terms of numbers of individual birds, Lapland longspurs dominate the avifauna of Aulavik National Park. Black-bellied plover is consistently ranked between second and fourth place in all estimates. It clearly should be judged as the second most common bird species on these study areas. There is a significant step down in relative abundance to horned lark (Eremophila alpestris) and Baird's sandpiper (Calidris bairdii) (Newman-Keuls test, P < 0.10). Horned lark and Baird's sandpiper show a relative abundance nearly equal to each other and are tied for third place on these areas (Figure 2). Horned lark, however, shows more variation in its relative abundance than does Baird's sandpiper. Long-tailed jaeger (Stercorarius longicaudus) on average is ranked fourth in relative abundance, but shows some variation from locale to locale (Figure 2). It was more abundant on the Muskox River study area and on the Thomsen River study area and less abundant near the Eames River. There is a significant step down in relative abundance to pectoral sandpiper (Calidris melanotos) and sandhill crane (Grus canadensis) (Newman-Keuls, P < 0.10). These two species are tied for fifth place, and both species exhibit relative abundance that is variable (Figure 2). The abundance of sandhill cranes may be biased because of the long distances over which sandhill cranes can be detected both visually and by vocalizations. Observers in this study made a concerted effort to record each sandhill crane on only one point count. Red phalarope (Phalaropus fulicaria) and glaucous gull (Larus hyperboreus) are tied for sixth place, and they both show a relative abundance that is only slightly less than pectoral sandpiper and sandhill crane. The relative abundance of red phalarope is slightly more variable than that of glaucous gull. There is a minor decrease in relative abundance (Newman-Keuls test, P > 0.10), and then three species are tied for seventh place and show almost equal relative abundance: lesser golden plover (Pluvialus dominica), king eider (Somateria spectabilis) and Pacific loon (Gavia pacifica) (Figure 2). The lesser golden plover and Pacific loon show little variation in their relative abundance. The king eiders were mostly females raising young on the inland areas of Banks Island while the males during summer tend to congregate along the coast. Finally, the black brant (Branta bernicula nigricans) is ranked the least common of these avian species. However, it shows considerable variation, being relatively common on the Muskox River study area, where a flock of over a hundred birds was observed repeatedly on a small lake. The composition of the avian community varies as ecological conditions in different parts of Aulavik National Park change. This pattern is illustrated by the fact that some of the relatively common bird species analysed in Figure 2 are found to be uncommon (Baird's sandpiper, pectoral sandpiper, lesser golden plover, king eider, Pacific loon and black brant) or even rare (red phalarope) in Table 1. The point counts were carried out in biologically productive areas of the park, while the daily checklists were carried out in park areas varying from polar deserts to more productive river valleys. Clearly the relative abundance of avian species as well as the composition of the avian community respond to the variation of ecological conditions found in different areas of the park. Further analysis of these patterns should be the focus of future research. |
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The point counts also documented the habitat association patterns for these thirteen avian species on these biologically productive study areas (Table 2). The data supports the conclusion that arctic bird species tend to be habitat generalists. In this study, over two thirds of the bird species examined (9 out of 13 species) showed no significant preference for a habitat type (Newman-Keuls test, P > 0.10). On the other hand, Lapland longspur, horned lark, glaucous gull and black-bellied plover were significantly associated with certain habitat types (Newman-Keuls test, P < 0.10), and these patterns can be summarized as follows: Lapland longspurs were most abundant on hummocky tundra (HT) and graminoid-dwarf shrub tundra (GST) but seemed to avoid water bodies (WB), sparsely vegetated ground (SVG) and dwarf shrub-lichen barrens (DLB) (see Ferguson, 1991, and Henry and Mico, 1997, for a detailed description of these habitat types). Horned larks were similar to but not identical with the Lapland longspurs. Horned larks were most abundant on hummocky tundra (HT), graminoid-dwarf shrub tundra (GST) and dwarf shrub-lichen barrens (DLB). However, this species seemed to avoid water bodies (WB), wet sedge meadow (WSM) and graminoid tundra (GRT) -- all habitat types with high surface moisture. Glaucous gulls are a wide-ranging species especially while foraging. However, they were most commonly observed on water bodies (WB) where they were observed to nest on small islands in medium to large tundra ponds. They were also frequently associated with mesic sites such as graminoid tundra (GRT) and graminoid-dwarf shrub tundra (GST), but they seemed to avoid sparsely vegetated ground (SVG). Black-bellied plovers also avoided sparsely vegetated ground (SVG). This species appeared to be adapted to a wide range of moisture conditions as exhibited by its association with water bodies (WB), wet sedge meadows (WSM), graminoid tundra (GRT), graminoid-dwarf shrub tundra (GST) and dwarf shrub tundra (DST). The point count data classified by habitat type for all birds sighted show that certain habitat types support a significantly higher density of birds than others (Friedman's ANOVA, P < 0.05). The data shows a rough correlation between available surface moisture and avian density: habitat types with the highest surface moisture show the highest abundance of birds. Water bodies (WB), graminoid-dwarf shrub tundra (GST), graminoid tundra (GRT) exhibit the highest density of birds and all have good moisture content. Wet sedge meadow (WSM) is an exception to this pattern; this habitat type shows intermediate avian density but has a high moisture content. Finally, sparsely vegetated ground (SVG), dwarf shrub-lichen barrens (DLB) and dwarf shrub tundra (DST) show the lowest density of birds and have the driest surface moisture conditions. Vegetation cover (which is also related to available surface moisture) also appears to be a good predictor of the density of birds in certain habitats: terrestrial sites with 75 percent or less vegetation cover exhibit the lowest avian densities. In descending order of vegetation cover and avian abundance, these habitat types include dwarf shrub tundra (DST), dwarf shrub-lichen barrens (DLB) and sparsely vegetated ground (SVG). |
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On gently rolling tundra, such as the terrain that makes up many areas of Aulavik National Park, finding shelter from the wind can be critically important to many plants and animals (Pielou, 1994). During a typical arctic summer, strong windstorms accompanied by near-freezing temperatures and rain or snow can last for a week or longer before abating. Reducing heat loss and minimizing energy expenditure during these storms may be critical to the survival of small birds and their offspring (Rodrigues, 1994). Wiersma and Piersma (1994) and Rodrigues (1994) discuss the importance of energy-conserving behaviours such as the selection of nest sites in a variety of tundra bird species. During this study we observed several pairs of Lapland longspurs and snow buntings nesting in hummocky tundra or other small micro depressions. Aboriginal people and naturalists have often observed that small birds on the tundra seem to disappear during periods of high winds. When a person walks through hummocky tundra during these times, Lapland longspurs, horned larks and other small birds seem to explode into flight just in front of the person. Given these observations, the hypothesis was suggested that hummocky tundra and other micro depressions might be important for providing shelter for small birds while nesting as well as shelter for them during windstorms. To test whether these microhabitats provide shelter from the wind, 35 micro depressions in hummocky tundra were chosen, and the wind profile was measured from 150 cm above ground to the bottom of these micro depressions (see Methods). Figure 3 presents the averages and standard errors for these measurements. Highly significant differences occur among these means (single factor ANOVA, P < 0.0001). Average wind speed at the bottom of the micro depressions is 1/20th of what it is at 150 cm above ground and nearly 1/10th of wind speed at ground level. Protection from the wind is not a simple function of depth; it is also a function of the verticalness of the walls and the sharpness and overhang of the edges of the micro depression. Nine micro depressions with these favourable features were measured, and wind speed was reduced to approximately 1/1000th of what it was 1.5 m above ground. Consequently, by carefully choosing the micro depression that they nest in or the one that they occupy during a windstorm small passerines can gain considerable shelter from the wind helping to reduce the energy they expend as a result of heat loss. How do larger birds (e.g., sandhill cranes, geese and ptarmigans) and for that matter mammals that do not den underground (e.g., muskoxen and caribou) find shelter during these prolonged periods of high wind and precipitation? In Aulavik National Park, deep and narrow coulees occasionally form along small creeks that flow into larger rivers. During a twelve day period of wind, rain and snow in early August, 1995, one of us (JDH) observed a pair of sandhill cranes, a common raven (Corvus corax) and a ptarmigan (Lagopus spp.) standing in the bottom of one of these coulees for more than five hours. They were feeding only infrequently. Most of the time they were simply standing quietly, within 10 m of each other, apparently seeking shelter from the storm. The results of the paired transects (see Methods) presented in Table 3 indicate that large birds and certain mammals are spending selectively more time in these coulees than in the open tundra areas immediately adjacent to them (paired sample t-test for each coulee sampled, P < 0.01). Further field observations are necessary to document whether these coulees are being selectively used by large birds and mammals during windstorms and other inclement weather. Narrow, deep coulees most often form where smaller drainages join a major river valley. Coulees that are oriented perpendicular to the prevailing winds, have sharp, steep walls and a narrow breadth seem to offer maximum shelter during windstorms. Coulees showing these attributes were extremely rare in the ten areas of the park examined. In conclusion, hummocky tundra might provide small birds microhabitat that offers protection from wind and other storms. Larger birds may use coulees as a place to find protection during windstorms and other inclement weather. These coulees also seem to be used selectively by certain mammals. Narrow, deep coulees that are oriented perpendicular to prevailing winds are rare landscape features in Aulavik National Park, and they may constitute important wildlife habitat. It is recommended that the use of these coulees by park visitors and staff or the development of park facilities near these coulees should be avoided so as not to impede access by large birds and mammals to these potentially important microhabitats. |
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