Bird of the Month: Violet-green Swallow
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
This Western North American Swallow has a white cheek and white on the sides of the rump which help separate it from the Tree Swallow.
Described as “a dainty feathered gem” by Arthur Cleveland Bent (1963b), the Violet-green Swallow exhibits subtle hues of violet and green on its back contrasting with the white underside. Distinguishing field marks include white feathers which curl onto the face from behind the ear and above the eye, and others rising over the sides of the rump. In flight, the Violet-green cruises at about 28 miles per hour in what appears to be a buoyant flight marked by quicker wingbeats and less soaring than the Tree Swallow (T. bicolor) (Brown et al).
The two birds share the genus Tachycineta from the Greek for swift mover: takhus, swift or quick, and kineo, move, reference the speed of flight. The species name thalassina, from the Latin, refers to the sea-green color of this bird (Helm). The name swallow is from the Anglo-Saxon swalewe, their name for this type of bird (Halloway). Photos, videos, and vocalizations of Violet-green Swallows can be found at the Macaulay Library.
ADAPTED TO VARIED HABITATS
Violet-green Swallow
Scientific Name: Tachycineta thalassina
Length: 5.25”
Wingspan: 13.5”
Weight: 0.49 oz (14 g)
AOU Alpha Code: VGSW
Violet-green Swallows migrate in early spring arriving in Washington around the first week of April. Initially, the flocks congregate near low elevation ponds or lakes (Wahl et al). From there, they gradually move to a variety of habitats including open areas of forests, rocky cliffs, and sometimes prairies if nest holes in trees exist. They often nest in colonies of 25 or so and will sometimes share a location with Tree Swallows or White-throated Swifts. They have also become accustomed to using birdhouses and human-made structures.
Early records provide some examples of nesting locations. In 1909, an observer remarked that in
Eastern Washington, these swallows nest “to a large extent upon the granite and lava cliffs.” While in the vicinity of Seattle and Tacoma, they have benefited from human development. In 1903, an observer noted that nests were found in an unused house and another in a log cabin (Bent, 1963b).
CAVITY NESTER
The female Violet-green Swallow builds a cup nest of grasses and feathers in a convenient cavity, such as an old woodpecker hole, a natural hollow in a tree, or in a crevice in rocks. Usually, 4-6 white eggs are deposited. The female provides most, if not all, of the incubation for about two and a half weeks. The young leave the nest in another four weeks.
The Violet-green Swallow’s diet is limited to insects but includes a wide variety of flies, beetles, wasps, winged ants, moths, and other flying bugs. Young swallows are dependent after hatching and adults must bring insects to the nest. It takes time for young birds to master the skill of catching insects in mid-air. To compensate for learning period, adults continue feeding for a time after fledging (Kaufman).
Southward migration can begin as early as August, but many Violet-green Swallows will remain north until October, staying in the breeding grounds longer than Tree Swallows will.
STATUS AND DISTRIBUTION
The Violet-green Swallow breeds in Western North America from Alaska to Northwest Mexico and winters from there to Guatemala. It is widespread in Washington and is more common than the Tree Swallow (Wahl et al). The population appears to be stable and there are no conservation measures in place. However, there is little research conducted on Violet-green Swallows and more is warranted as most aerial insectivorous birds are affected by reduced insect populations in North America.
Photo credit: Mick Thompson
References available upon request from amccormick@eastsideaudubon.org.
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