Evening Grosbeak - Coccothraustes vespertinus
Evening Grosbeak, Female - Coccothraustes vespertinus - Perched in a tree
General Description
A large (20-cm-long), robust finch with a large thick bill (pale yellow or greenish in spring and summer, whitish in fall and winter), black tail, black wings with white patch on inner wing, and yellow wing linings; adult male has yellow forehead and eyebrow, and dark brown and yellow body; female is grayish-tan, with a thin dark whisker stripe, white-tipped tail, and a conspicuous (in flight) second white patch on the primaries; juvenile has a brown bill, with each sex resembling the adult of the same sex (though juvenile male is significantly duller than adult male); loud call, clee-ip or peeer (NGS 1983).
Distribution
Montana Range
Migration
In Bozeman area normal vertical movements are Aug 20-Nov 1 and around June 1.
Habitat
In the rocky Mtns., common in mixed-conifer and spruce-fir forests, less common in pine-oak, pinon, Cascadian, ponderosa pine and aspen forests. Less closely tied to coniferous tree species than other carduelines-also uses deciduous species for nesting and food (Gillihan, Scott W., and Byers, Bruce, The Bird of North America, No. 599, 2001).
Food Habits
Invertebrates, especially spruce budworm and other larvae; wide variety of small fruits and seeds, especially maples (Gillihan and Byers 2001).
Reproductive Characteristics
Nests primarily in trees but also in shrubs, a spare structure, shaped like flattened saucer. Eggs are subelliptical in shape, light blue to blue-green with brown to purplish markings, smooth and glossy. Clutch size ranges 2-5, usually either 3 or 4 (Gillihan and Byers 2001). Near Fortine, dependent young seen flying Jul 26. Partly fledged young seen Jul 3. Nesting dates probably similar to those for Colorado: early Jun-late July.