KILBUCK AND AHKLUN MOUNTAIN BIRDS 



15 



Species thought to winter in the area have been indicated as wr? 

 Spring migrant adults generally appear in April-May, whereas spring 

 migration for subadults of some species may not occur until late May or 

 June when breeding birds have begun nesting. Similarly, fall migration 

 for some species (particularly shorebirds) may commence with the 

 occurrence of subadults and failed breeders while adults are still raising 

 young; thus, fall migration can occur as early as June and as late as 

 October. We refer to summer as the period after snowmelt when most 

 species are nesting. Winter is the time from freeze-up to early break-up; 

 this is generally from October to March and is characterized by extensive 

 snow cover on land; ice formation on ponds, lakes, rivers, and lagoons; 

 and persistent snow fall. We give dates of earliest and latest observations 

 for all but rare or very rare species. These dates may reflect when the 

 species occurs but, in part, also reflect our own seasonal presence at 

 locations. 



Rates of migration were estimated from observations of birds pass- 

 ing the cliffs at Cape Peirce from late April until early September. 

 Observations in 1976 were 2-hour sessions conducted on alternate days 

 similar to that described by Herter et al. (1989). In 1970 and 1973, 

 observations were conducted when an increase in migrants was ob- 

 served. Densities of passerines at Cape Peirce are estimated from a 

 transect (3.4 km long, 184 ha) crossing the peninsula from Nanvak Bay 

 toward Hagemeister Island and another (1.6 km long, 86 ha) following 

 the western cliff edge. The number of birds, species, behavior, and 

 status of nests were determined along the cape transect at irregular 

 intervals in 1973 (9 surveys) and weekly at each transect in 1976 

 (33 surveys). Birds at the Tuluksak River were surveyed in 1983 by the 

 fixed-width strip census method in plots totaling 130 ha. Comparisons 

 were made of densities of passerines in 1 3 plots disturbed by mining 

 activity to 13 plots in nearby undisturbed areas. When possible, data are 

 presented as mean ±SE. 



Specimens have been deposited with the University of Alaska Mu- 

 seum (UAM), Fairbanks; Yukon Delta National Wildlife Range, Bethel, 

 Alaska (YDNWR); Department of Wildlife and Fisheries Biology Mu- 

 seum, University of California (WFB), Davis; British Museum (Natural 

 History) (BMNH), Trint; and Royal Museum of Scotland (RMS), Edin- 

 burgh. More complete specimen data can be obtained from the authors. 

 Species documented by photographs are noted by photographer 

 (e.g., nest, eggs; DNW photo). 



Scientific names and taxonomic order of birds follow American 

 Ornithologists' Union (1983) with exceptions as noted. Scientific names 

 of mammals follow Banks et al. (1987) and of plants follow Hulten 

 (1968). Zoogeographic affmities of birds are from Kessel (1989). Classi- 

 fication of habitats follows Kessel (1979). Place names are from USGS 



