About the Violet-Green Swallow
The western counterpart of the tree swallow, the violet-green swallow has narrower wings and a shorter tail. This species frequently uses nest boxes. Polytypic (3 ssp., none separable in the field; lepida in North America). Length 5.3".
Adult male: upperparts of male are dark velvet green, more bronze on the crown, becoming purple on rump and uppertail coverts. Underparts are white, extending onto cheek, to behind and above the eye. Lores are dusky. White of flanks extends onto the sides of the rump, forming 2 white patches from above in flight. Wings and short, slightly forked tail are black. Underwing coverts grayish. Adult female: Somewhat duller than the male, browner on the head, face and ear coverts. Throat is washed slightly with ashy brown. Juvenile: similar to adults, but green and purple are replaced with brownish. White on cheek and behind eye is much less extensive. Slight pale brownish wash on breast. Tertials and inner secondaries are very narrowly edged pale grayish. Flight: longer, narrower wings and shorter tail than the tree swallow; the violet-green has a more fluttering flight style.
The tree swallow is larger, entirely greenish blue above, and lacks white around the back of the eye and on the sides of the rump. The larger white-throated swift has narrower pointed wings and black-and-white underparts.
Call: various short notes, including a twitter, and chee-chee notes. Alarm call is a zwrack similar to that of the purple martin.
Status and Distribution
Common. Breeding: occurs in a variety of habitats, including open areas in montane coniferous and deciduous forests, coastal regions, and even in higher elevation desert areas. Nest: it brings a variety of grasses and stems, as well as feathers, to an abandoned cavity in trees, rock crevices, dirt banks, or columnar cactuses; 4–6 eggs (April–May). Migration: in spring, arrives in southern Arizona and southern California by late February, Alaska by early May. Departs Alaska by mid-August, lingering into mid-October in British Columbia and Washington. In the Southwest departs late September–late October. Winter: tidal flats to interior mountains. A few birds in southern California, but most from Mexico south to Guatemala, El Salvador, and Honduras. Vagrant: casual in western Alaska and east of the Rockies, with most sightings in the East September–November.
There is no documented effect of human activity on numbers; the introduction of the house sparrow and European starling may have reduced populations in urban areas of southern Canada.
—From the National Geographic book Complete Birds of North America, 2006