Sm. Matsuoka et al., THE RELATIVE IMPORTANCE OF NESTING AND FORAGING SITES IN SELECTION OFBREEDING TERRITORIES BY TOWNSEND WARBLERS, The Auk, 114(4), 1997, pp. 657-667
We investigated habitat selection by the Townsend's Warbler (Dendroica
townsendi), a Neotropical-Nearctic migrant that breeds primarily in m
ature coniferous forests. From 1993 to 1994, we compared the features
of habitat selected for nest sites and foraging sites with those selec
ted for territories in mature, mixed coniferous-deciduous forests in s
outh-central Alaska. We also tested the prediction that large conifers
are selected for nesting and foraging sites. Females placed nests in
relatively large white spruce (Picea glauca) and consistently chose ne
st trees that were within areas of higher densities of large white spr
uce than were generally available. Nesting areas also had a higher den
sity of small white spruce than was generally available, which may hav
e been important in concealing nests from predators. Vegetation featur
es selected for foraging differed from those selected for nesting and
varied seasonally. Foraging was concentrated in medium-sized white spr
uce during the prehatching stage and became more generalized across co
niferous and deciduous vegetation during the posthatching stage. Adult
s foraged in large white spruce in direct proportion to their availabi
lity on the study areas. Territories, which encompassed both nesting a
nd foraging areas, were heterogeneous in vegetation structure and flor
istics. Areas selected for territories clearly reflected availability
of the large white spruce selected for nest sites but did not reflect
selection of medium white spruce for foraging. Characteristics of habi
tats varied with specific resource needs, but the distribution of Town
send's Warblers was most strongly related to specific habitat requirem
ents for nest sites.