Brown-headed Cowbird Molothrus ater Boddaert       Field Guide IDs: NG-440; G-300; PE-252; PW-pl 52; AE-pl 571; AW-pl 620; AM(III)-306 Nest Location Nest Type Eggs & Mating System Dev. & Parental Care Primary & 2ndary Diet.. Foraging Strategy PARASITE HOST I: 10-13 DAYS ALTRICIAL SHRUB (To 3 feet) MONOG POLYGYN PROMISC 4-5 (1-7) F: 10-11 DAYS HOST SEEDS BREEDING: Woodland, forest (esp decid), forest edge, grassland. DISPLAYS: Courting male ruffles feathers of upper body, bows toward female, and calls. In air, male ruffles feathers as on ground, bends head, arches wings and sings. On elevated perch, male points bill straight up, fluffs feathers on nape, breast, and flanks, sings, then arches neck, spreads tail, raises wings, and bows. NEST: Does not build nest; deposits eggs in nests of other species, esp flycatchers, warblers, finches, and vireos. EGGS: White to grayish-white, marked with browns. 0.8" (21 mm). DIET: Includes spiders, few snails; grain, grass and forb seeds. CONSERVATION: Winters s to s Mexico. Range has expanded e and w from Great Plains with clearing of forests and introduction of cattle, with which it is now assoc (originally assoc with American bison). NOTES: See Cowbirds. Highly gregarious at all seasons; postbreeding fall flocks generally 50-200. Feeds and roosts in enormous flocks with other blackbirds and starlings, esp in winter. STANFORD. NOTES: Fairly common breeder in a variety of habitats virtually throughout campus, less common during the nonbreeding season. Laying its eggs in the nests of other species, the Brown-headed Cowbird has been observed parasitizing the California Towhee (the most frequent cowbird host) and [OBSERVERS ADD OTHER SPECIES] on campus. ESSAYS: Brood Parasitism; Conservation of Kirtland's Warbler; Communal Roosting; European Starlings; Range Expansion REFERENCES: Darley, 1982; Friedmann and Kiff, 1985; Teather and Robertson, 1986.