Brewer's Blackbird Euphagus cyanocephalus Wagler       Field Guide IDs: NG-440; G-298; PE-254; PW-pl 52; AE-pl 570; AW-pl 622; AM(III)-298 Nest Location Nest Type Eggs & Mating System Dev. & Parental Care Primary & 2ndary Diet.. Foraging Strategy F I: 12-14 DAYS ALTRICIAL GROUND SHRUB 0 - 150 feet F 4-6 (3-7) MONOG (POLYGYN) F: 13-14 DAYS MF SEEDS FRUIT FOLIAGE GLEAN HAWKS BREEDING: Shrubby, brushy areas (esp near water), riparian woodland, aspen parks, cultivated lands, marshes, around human habitations. 1, occ 2 broods. DISPLAYS: Courtship (or threat between birds of same sex): male, occ female, holds bill horizontally or pointed upward, fluffs body feathers, spreads wings, tail, and vocalizes. NEST: Variably placed; also occ in decid tree, emergent marsh veg; sturdy, of twigs, grass, matrix of mud or cow dung, lined with fine materials. EGGS: Grayish, marked with brown. 1.0" (25 mm). DIET: Includes few spiders, also crustaceans, snails; grass and some forb seeds. Young fed 90% insects, spiders. Occ wades to feed. CONSERVATION: Winters s to s Mexico. Common cowbird host. Increased range and abundance with spread of agriculture; expanding eastward. Often assoc with humans, using urban, suburban, agricultural habitats. NOTES: Nests in colonies of 3 - 100 pairs. Pairs often rejoin for up to 5 yr. Monogamous females tend to remain monogamous; secondary females of polygynous males tend to remain polygynous but change males yearly. Male occ feeds incubating female. Incubation occ starts before clutch completed, causing hatching to take up to 3 days. Large winter flocks with other blackbirds, esp Red-winged and Tricolored, but greatly outnumbered by them. STANFORD. NOTES: Common to abundant resident in a variety of habitats virtually throughout campus. ESSAYS: Feeding Birds; Eye Color and Development; Redwing Coverable Badges; Polygyny; Coloniality; Range Expansion REFERENCES: Balph, 1975; Furrer, 1975; Horn, 1968; Orians, 1985.