Violet-green Swallow Life History

Habitat

Habitat Open WoodlandsViolet-green Swallows breed in open evergreen and deciduous woodlands, especially woodlands with standing dead trees that feature woodpecker holes or other natural cavities. They breed across the western United States from sea level to as high as 11,500 feet elevation. In some areas, they also breed in and around human settlements and use nest boxes. In Mexico and Central America during the nonbreeding season, Violet-green Swallows inhabit coastal plains, interior mountains, cloud forests, and pine forests up to 10,000 feet. Back to top

Food

Food InsectsViolet-green Swallows feed on flying insects such as flies, leafhoppers, leafbugs, aphids, beetles, and winged ants that they catch and eat in midair. They skim low over water bodies and fields snatching up insects, but they also forage high above the ground. Back to top

Nesting

Nest Placement

Nest CavityViolet-green Swallows nest in cavities in trees and cliffs, or in nest boxes. They use old woodpecker holes or naturally occurring cavities in dead and dying trees. They nest solitarily or in small colonies of up to 25 pairs in open woodlands often near water bodies.

Nest Description

Male and female swallows gather grass stems, small twigs, rootlets, and feathers to build a loose, shallow cup nest at the bottom of a cavity. Nest construction takes anywhere between a few days up to 20 days. The nest cup measures about 3 inches across, but depends to some extent on cavity size.

Nesting Facts
Clutch Size:4-6 eggs
Number of Broods:1-2 broods
Egg Length:0.6-0.8 in (1.6-2.1 cm)
Egg Width:0.5-0.6 in (1.2-1.4 cm)
Incubation Period:14-15 days
Nestling Period:23-24 days
Egg Description:Pure white, without markings.
Condition at Hatching:Naked with closed eyes and bits of fluffy down on the back, crown, and scapulars.
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Behavior

Behavior Aerial ForagerViolet-green Swallows are gregarious birds all year long, on the breeding and nonbreeding grounds and during migration. They often forage in large groups, of up to several hundred, with other Violet-green Swallows as well as other swallow and swift species. They forage over water bodies, fields, and open woodlands capturing and eating insects on the wing. In flight, these swallows intersperse rapid, shallow wingbeats with long glides and appear rather fluttery and slightly off balance. Like other cavity-nesting species, Violet-green Swallows often have more parasites on their feathers than birds that nest in the open. To control the parasites, they sunbathe and preen frequently. They breed solitarily or in groups, depending on the availability of nesting cavities. Adults compete with other cavity-nesting species including House Sparrows, Western Bluebirds, Tree Swallows, and Mountain Chickadees for places to nest. Pairs are likely monogamous during the breeding season, but females may sneak off to mate with additional males.Back to top

Conservation

Conservation Low ConcernViolet-green Swallows are common throughout the West, but populations experienced a decline of about 28% between 1966 and 2015, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 7 million, with 66% breeding in the United States, 16% in Canada, and 91% spending a portion of the year in Mexico. The species rates a 9 out of 20 on the Continental Concern Score and is not on the 2016 State of North America's Birds' Watch List. Although Violet-green Swallow populations are stable, aerial insectivores as a group were recognized as declining across North America in the State of the Birds 2014 report. Aerial insectivores have declined across much of North America and Europe perhaps due to use of neonicotinoids (an insecticide), climate change, and pollution. All of these factors can reduce the abundance of flying insects that these birds rely on and could contribute to population declines. Back to top

Backyard Tips

If you live near an open woodland or lake, Violet-green Swallows may nest in your yard, especially if you put up a nest box or leave standing dead trees on your property. Nest boxes can be placed on buildings, live trees, dead trees, or a pole 9-15 feet above the ground. Because Violet-green Swallows often like to nest in small groups, consider putting up more than one nest box at least 30 feet apart. Find out more about nest boxes on All About Birdhouses, where you'll find plans to build your own nest box for Violet-green Swallows.

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Credits

Brawn, J. D. 1990. Interspecific competition and social behavior in Violet-green Swallows. Auk no. 107:606-608.

Brown, Charles R., A. M. Knott and E. J. Damrose. 2011. Violet-green Swallow (Tachycineta thalassina), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Cottam, C., C. S. Williams and C. A. Sooter. 1942b. Flight and running speed of birds. Wilson Bull. no. 54:121-131.

Dunne, Pete. 2006. Pete Dunne's essential field guide companion: Houghton Mifflin Harcourt.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Nebel, S., A. Mills, J. D. McCracken and P. D. Taylor. Declines of aerial insectivores in North America follow a geographic gradient (5:1). Avian Conservation and Ecology - Écologie et conservation desoiseaux 2010.

North American Bird Conservation Initiative. 2014. The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.

Partners in Flight. 2017. Avian Conservation Assessment Database. 2017.

Sauer, J. R., D. K. Niven, J. E. Hines, Jr. Ziolkowski, D. J., K. L. Pardieck, J. E. Fallon and W. A. Link. The North American breeding bird survey, results and analysis 1966-2015 (Version 2.07.2017). USGS Patuxent Wildlife Research Center 2017.

Sibley, David Allen. 2014. The Sibley guide to birds, second edition. Alfred A Knopf, New York.

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