Animal Field Guide

Tree Swallow

Tachycineta bicolor
(Hirundinidae)

Global Rank: G5
State Rank: S5B

Agency Status
USFWS:
USFS: none
BLM: none

Medium-sized swallow, tail not sharply forked. Total length, tip of bill to tip of longest tail feather is about 14.0 cm. Bicolor. Mostly steely greenish blue above, white below. Upperside body feathers either iridescent greenish blue (males and older females) or mixture of brown and greenish blue. A highly social bird. Outside the breeding season, it often forms large flocks, up to several hundred thousand birds at some nighttime roosts. (Robertson, R. J., Stutchbury, B. J., and Cohen, R. R. The Birds of North America, No. 11, 1992).

In the Bozeman area, normal migration periods are from April 9 to May 15 and August 10 to September 1.

Open fields, meadows, marshes, beaver ponds, lakeshores and other wetland margins. Uses trees only for nesting and occasional roosting. (Robertson, Stutchbury and Cohen 1992).

Mostly flying insects, though vegetable matter is eaten during unfavorable weather conditions. Forage over open water, marshes, ponds, and fields, as well as in shrubby habitat. (Robertson, Stutchbury and Cohen 1992).

Usually one brood per year. A hole nester. It depends on woodpeckers and other species that excavate and abandon cavities in dead trees (typically along beaver ponds and wetland margins) and to a lesser extent on nest boxes. Mean clutch size 5.46. (Robertson, Stutchbury and Cohen 1992). Near Fortine, egg dates are May 15 to June 12. Young left the nest June 23 to July 10. Statewide, incubation is usually in late June and early July.