Tree Swallow Tachycineta bicolor Vieillot       Field Guide IDs: NG-322; G-220; PE-204; PW-pl 43; A-pl 331; AW-pl 356; AM(II)-300 Nest Location Nest Type Eggs & Mating System Dev. & Parental Care Primary & 2ndary Diet.. Foraging Strategy F I: 13-16 DAYS ALTRICIAL 5 feet + F -M 4-6 MONOG POLYGYN F: 20 (16-24) DAYS MF BERRIES FOLIAGE GLEAN BREEDING: Open country, woodland edge, usu near water. 1 brood, rarely 2. DISPLAYS: Complex courtship flight. NEST: In tree hole or other cavity; of grass, often lined with feathers. EGGS: White, unmarked. 0.8" (19 mm). DIET: Berries taken when insects unavailable. Occ glean ground. CONSERVATION: Winters s to Honduras, Nicaragua, and c Costa Rica. Rare cowbird host. Forestry practice of removing standing dead trees has greatly reduced availability of natural nest sites; will use nest boxes. NOTES: Often nest in loose colonies. Occ polygynous, possibly when food supplies are superabundant. Juveniles often seen as attendants at nonkin nests but do not serve as helpers -- in fact, they attempt to steal food from nestlings and parents! Clutch size larger and nestling survival greater when food very abundant. Hatch asynchronously. Nestlings brooded by female for 5 days. Starlings, House Sparrows, House Wrens, bluebirds compete for nest cavities. Only N.A. passerine in which females do not attain full breeding plumage at one year. Form large premigratory communal roosts; huge flocks perform preroosting aerial displays. STANFORD. NOTES: Uncommon forager around campus from spring through fall, often with flocks of Violet-green and other swallows. Often breeds near water, and perhaps could nest near Lagunita some years, although breeding has not been confirmed on campus [ANY BREEDING RECORDS?]..... Similar Species: Violet-green Swallow ESSAYS: Cooperative Breeding; Polygyny; Brood Reduction; Variation in Clutch Sizes; Communal Roosting REFERENCES: Hussell and Quinney, 1987; Leffelaar and Robertson, 1986; Lombardo, 1987; Quinney, 1986.