KILBUCK AND AHKLUN MOUNTAIN BIRDS 



129 



Discussion 



Here we provide documentation for the expansion of breeding 

 distribution (known or possible) of several species described by the 

 American Ornithologists' Union (1983), reported by Kessel and Gibson 

 (1978), or not previously reported: fork-tailed storm-petrel, double- 

 crested cormorant, red-faced cormorant, brant, king eider, white-tailed 

 ptarmigan. Pacific golden-plover, black-bellied plover, lesser yellowlegs, 

 Say's pheobe, and Bohemian waxwing. Some species such as double- 

 crested cormorant, red-faced cormorant, brant, and black-bellied plov- 

 ers nested annually, whereas the others (fork-tailed storm-petrel, king 

 eider, white-tailed ptarmigan, etc.) nested or were thought to nest 

 (Bohemian waxwing) only in some years. 



We also document unusual occurrences for frigatebird, Baikal teal, 

 American kestrel, bristle-thighed curlew, Terek sandpiper, rufous hum- 

 mingbird, and red-winged blackbird. The bristle-thighed curlew prob- 

 ably migrates through the area each fall, whereas the other species are 

 truly unusual occurrences. There is little evidence to suggest that spe- 

 cies that are apparently new to the area, but that occur annually, 

 represent recent expansion of their ranges. As at many remote locations 

 in Alaska, an increase in field studies results in documentation of species 

 generally found in low numbers or restricted habitats. Species found 

 either nesting or present outside their normal ranges are generally 

 thought to be a result of storms (birds being "blown in"), fluctuations 

 in conditions at the usual nesting area (prairie droughts), or sporadic 

 increases in population numbers (low winter mortality). It is probable 

 that the distributions of these species will be further clarified as more 

 and more people visit the area and as the number and intensity of field 

 studies in the area increases. 



The 140 breeding or probably breeding birds of the Ahklun and 

 Kilbuck mountains and offshore islands are predominantly of North 

 American (58%; A^= 81) zoogeographic affinity (Table 7). Several nesting 

 forms are of Beringian (24%; = 33) and Panboreal affinity (17%; 

 N = 24), with the remainder of Old Worid affinity (1%; = 2). Among 

 44 species of fairly-common-to-abundant migrants and visitants in our 

 area, the North American group is best represented (4l% of 44 species), 

 while Panboreal and Beringian elements are approximately equally 

 represented (Table 8). These proportions of breeding birds and migrants 

 are similar to those of regularly occurring breeding birds and visitants 

 on the Seward Peninsula (Kessel 1989) and reflect the similar forces 

 operating in the entire region over geologic time. 



