Violet-green swallow

Appearance

The distinct body form of swallows distinguishes them from other passerine birds. Their long pointed wings and slim, streamlined body evolved to catch insects while in flight. The body of the violet-green swallow is no exception. With an average body length of 5¼ in. , the violet-green swallow is slightly shorter and appears more compact in flight compared to other members of the Hirundinidae family. The violet-green swallow most closely resembles the North American tree swallow, but can be distinguished by its shorter wings and colouration.

Naming

Violet-green swallows are divided into three subspecies, ''T. t. thalassina'', ''T. t. brachyptera'' and ''T. t. lepida'' differing in breeding ranges and wing length. ''T. t. thalassina'' has slightly longer wings and has been known to breed as far north as Alaska, while the shorter winged ''T. t. brachyptera'' breeds further south in California and Mexico. Not all of the literature agrees upon ''T. t. lepida'' as a 3rd subspecies, and little information is available to help distinguish it from other subspecies.

Distribution

Violet-green swallows are a predominantly western species, with the rare sighting of individuals in eastern North America. The distribution of the species can be divided based on the recognized subspecies, but the entire range spans from central Alaska down to Mexico. Longitudinally, the range borders the west coast of Alaska, British Columbia and the United States, and extends eastward into southwestern Alberta, Montana, the Dakotas and Texas. The breeding range spans almost the entire distribution, while the winter range is restricted to Mexico.

Habitat

The type of habitat occupied by violet-green swallows varies depending on their geographical location and elevation. Across their range, these birds can be found in deciduous, coniferous and mixed forests, as well as within canyons and in close proximity to large cliffs. Breeding and non-breeding habitats do not differ much except that breeding habitat is usually at lower elevations. Violet-green swallows have also been observed nesting around buildings in more settled areas.

Reproduction

Violet-green swallows will usually arrive to their breeding area weeks prior to the start of reproduction. Location dependent, copulation takes place mid-May with the eggs being laid by the start of June, followed by a couple weeks of incubation before hatching. The average clutch size is 5 eggs, with females laying approximately 1 per day. During the weeks post-hatching, their parents feed the young as they slowly begin to grow their feathers. After approximately 3 weeks the young are ready to leave the nest. It is more common for pairs to reproduce once per breeding season, but a second brooding has been observed on occasion.

Food

Similar to other swallows, violet-green swallows are specialized aerial insectivores, catching and eating their prey while in flight. However, they have been known to feed higher in the sky than most other swallows.The examination of the stomach contents of multiple individuals has presented a wide range of diet items, including insects like ants, beetles and flies as well as other arthropods such as spiders. On rare occurrences these birds have been observed foraging along the ground, but such events represent exceptions to their typical feeding habits.

Defense

Violet-green swallows are secondary cavity nesters, meaning they typically nest in natural holes or previously occupied nests. Some breeding pairs will even go as far as usurping nests from other species. A majority of violet-green swallow nests are in tree holes excavated by other animals or within the cracks of large cliffs. Due to their dependence on large trees, violet-green swallows are highly impacted by forest management practices. In addition to nesting in natural cavities, violet-green swallows have also been observed occupying artificial nest boxes. Pairs typically breed in independent nests, except on cliffs where large colonies can be found nesting together.