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Bird Bio: Tree Swallow

Tree Swallow (c) Jim Livaudais

By Anne Seiler, Banding Intern

The Tree Swallow is commonly encountered in natural open areas near trees and water throughout much of NorthAmerica during the summer months. They are recognizable from afar by their dark upper parts and white belly, sloped triangular wings, and distinctive swooping flight. A closer look at these aerial insectivores reveals brilliant iridescent purple and teal plumage. Tree Swallows are very social, often congregating in large mixed flocks with the closelyrelated Violet-green Swallow and other swallow species.

Tree swallows are found primarily in open spaces nearwater, avoiding dense woodlands and busy residential areas. Arriving in southern Oregon and northern California in late-winter to early spring from their wintering areas that range from the southern U.S. to Central America and the Caribbean, this swallow begins its search for a suitable cavity (or, hollowed out hole) nesting site. After one, or possibly two broods, they begin to gather into flocks often a thousand birds strong in July and August to begin their fall migration southward.

Tree Swallow populations are limited by the availability of cavity nesting sites, as their name suggests, in trees, or nest boxes. Placement of nest boxes has helped mitigate the loss of natural nest cavities due to habitat loss and declining woodpecker populations, which initially create cavities used by Tree Swallows and many other species. Although increasing slightly in North America as a whole since 1966, this swallow’s numbers have declined in Oregon during the same period according to Breeding Bird Survey data.

This article appears in the Fall 2008 KBO newsletter


Birds of Oregon, first edition 2003, edited by D.B. Marshall, M.G. Hunter, & A.L. Contreras; Complete Birds of North America, 2006, edited by Jonathan Alderfer Sauer, J. R., J. E. Hines, and J. Fallon. The North American Breeding Bird Survey, Results and Analysis 1966 – 2007, 2008, USGS Patuxent Wildlife Research Center.Tree Swallow Photo: James Livaudais