234
M.F. Willson et al.
ANOVA, F = 12.44, P = 0.002; Tukey post-hoc test showed that the
significant difference was found between Chiloe and Alaskan coniferous
forest). Mist-net samples from the understory, however, suggest either
that the denser populations of Chiloe occur chiefly in the upper strata of
the forest, or that the understory birds are more difficult to capture in
mist nets . The catch rate of birds in understory in Chiloe (0.13-0.22 birds
per mist-net hour) was uniformly lower than that for Alaskan deciduous
stands (0.36-1.05); the samples for Alaska coniferous stands (0.06-0.15)
were extremely low (one-way anova, F = 6.81, p = 0.037).
Composition
A number of taxonomic families are shared by the avifaunas of Alaska
and Chiloe forests, and both regions hold species of families and subfamilies not shared with the other region (e.g., Chiloe : Psittacidae,
Furnariidae, Rhinocryptidae; Alaska: Paridae, Sittidae, Certhiidae,
Bombycillidae, Vireonidae, Emberizidae-Parulinae, MuscicapidaeSylviinae). More interesting are genera shared by these widely separated
regions : Picoides, Colaptes, Turdus, Zonotrichia, Carduelis, Tachycineta,
and Troglodytes. Chile even has one species that occurs in much of North
America, although not in Alaskan coastal forests (Troglodytes aedon).
The most common species in the Alaskan deciduous stands were
Wi/sonia pusilla, Vermivora celata, and Dendroica coronata, ranking in
the top three for abundance in the majority of sites. In Alaska coniferous
stands, the most common species (top three at most sites) were Ixoreus
varius, Troglodytes troglodytes, and Dendroica townsendii . Five of these
six most common species are summer residents (and long-distance
migrants) in Alaska, and four belong to a single subfamily (EmberizidaeParulinae).
The most common species at all sites on Chiloe was the tyrannid
Elaenia albiceps, a summer resident and long-distance migrant (Johnson,
1967; Sabag, 1993). The chucao (Scelorchi/us rubecula; Rhinocryptidae)
ranked in the top three at three sites but was probably overestimated
because of its loud, ringing call. Also commonly ranked in the top three
were the only lowland hummingbird in the region (Sephanoides galeritus)
and a furnariid (Aphrastura spinicauda) .
Notable Biological Differences
One major difference between the avifaunas of southeast Alaska and
Chiloe is the high proportion of southeast Alaskan species that are longdistance migrants (see Table 11.1). Migrants comprise 38% to 67% of the
regularly occurring species in Alaskan coastal conifer forest and as much
as 72% to 83% of the species in deciduous forest . In contrast, longdistance migrants constitute less than 20% of the regularly occurring
M.F. Willson et al.
ANOVA, F = 12.44, P = 0.002; Tukey post-hoc test showed that the
significant difference was found between Chiloe and Alaskan coniferous
forest). Mist-net samples from the understory, however, suggest either
that the denser populations of Chiloe occur chiefly in the upper strata of
the forest, or that the understory birds are more difficult to capture in
mist nets . The catch rate of birds in understory in Chiloe (0.13-0.22 birds
per mist-net hour) was uniformly lower than that for Alaskan deciduous
stands (0.36-1.05); the samples for Alaska coniferous stands (0.06-0.15)
were extremely low (one-way anova, F = 6.81, p = 0.037).
Composition
A number of taxonomic families are shared by the avifaunas of Alaska
and Chiloe forests, and both regions hold species of families and subfamilies not shared with the other region (e.g., Chiloe : Psittacidae,
Furnariidae, Rhinocryptidae; Alaska: Paridae, Sittidae, Certhiidae,
Bombycillidae, Vireonidae, Emberizidae-Parulinae, MuscicapidaeSylviinae). More interesting are genera shared by these widely separated
regions : Picoides, Colaptes, Turdus, Zonotrichia, Carduelis, Tachycineta,
and Troglodytes. Chile even has one species that occurs in much of North
America, although not in Alaskan coastal forests (Troglodytes aedon).
The most common species in the Alaskan deciduous stands were
Wi/sonia pusilla, Vermivora celata, and Dendroica coronata, ranking in
the top three for abundance in the majority of sites. In Alaska coniferous
stands, the most common species (top three at most sites) were Ixoreus
varius, Troglodytes troglodytes, and Dendroica townsendii . Five of these
six most common species are summer residents (and long-distance
migrants) in Alaska, and four belong to a single subfamily (EmberizidaeParulinae).
The most common species at all sites on Chiloe was the tyrannid
Elaenia albiceps, a summer resident and long-distance migrant (Johnson,
1967; Sabag, 1993). The chucao (Scelorchi/us rubecula; Rhinocryptidae)
ranked in the top three at three sites but was probably overestimated
because of its loud, ringing call. Also commonly ranked in the top three
were the only lowland hummingbird in the region (Sephanoides galeritus)
and a furnariid (Aphrastura spinicauda) .
Notable Biological Differences
One major difference between the avifaunas of southeast Alaska and
Chiloe is the high proportion of southeast Alaskan species that are longdistance migrants (see Table 11.1). Migrants comprise 38% to 67% of the
regularly occurring species in Alaskan coastal conifer forest and as much
as 72% to 83% of the species in deciduous forest . In contrast, longdistance migrants constitute less than 20% of the regularly occurring