The Tree Swallow Audubon: A Guide to Identification.

Physical Characteristics and Range of Tree Swallows

The Tree Swallow, also known by its scientific name Tachycineta bicolor, is a small swallow species that is widespread across North America. These birds are approximately 5 to 6 inches long and have a wingspan of 11 to 13 inches. They are known for their iridescent blue-green feathers on their back and wings, with white underparts. Males and females look alike, with the males being slightly larger.

Tree Swallows are migratory birds that breed across North America, from Alaska to Newfoundland in the north and down to Mexico in the south. In the winter, they migrate to the southern United States, Central America, and the Caribbean. They are cavity nesters, often using natural tree cavities or nest boxes. They are commonly found in open habitats, such as fields, marshes, and meadows, and near bodies of water like lakes and rivers.

Nesting Habits and Diet of Tree Swallows

Tree Swallows are monogamous and form pair bonds during the breeding season. They typically lay 4 to 7 eggs per clutch, which are incubated by both parents for approximately 14 to 16 days. The chicks hatch naked and blind and are fed by both parents for about three weeks until they fledge. Tree Swallows are known to have more than one brood per season, with some pairs raising up to three broods per season.

Tree Swallows primarily feed on insects, including flies, beetles, and moths, which they catch in mid-air. They are aerial foragers and are often seen flying low over fields and water in search of prey. Tree Swallows have also been known to eat fruits and berries during the winter months when insects are scarce.

Vocalizations and Behavior of Tree Swallows

Tree Swallows are known for their high-pitched, musical twittering calls, which are often heard during flight. They are also known for their aerial acrobatics, performing impressive maneuvers like swoops, dips, and rolls during flight. They are highly social birds and are often seen in flocks, especially during migration.

Tree Swallows are also known for their aggressive behavior, especially during the breeding season. They will fiercely defend their nesting territories and will attack other birds, including other swallows and even larger birds like crows and hawks. They have also been known to attack humans who come too close to their nests.

Comparison with Other Swallows: ID Tips

Tree Swallows can be easily identified by their iridescent blue-green feathers and white underparts. They are often confused with other swallow species, including Barn Swallows and Cliff Swallows.

Barn Swallows have a deep blue-black back and wings, a rust-colored throat and forehead, and a deeply forked tail. They are also known for their distinctive long, pointed wings and deeply forked tail. Cliff Swallows, on the other hand, have a brownish-gray back and wings, with a cinnamon-colored forehead and throat. They have a square tail and a pale rump patch.

To differentiate Tree Swallows from these other swallow species, focus on their iridescent blue-green feathers and white underparts. Their wings are shorter and more squared off than Barn Swallows and their tail is less deeply forked. They also lack the cinnamon-colored forehead and throat of Cliff Swallows.

Conservation Status and Threats to Tree Swallows

Tree Swallows are currently listed as a species of "least concern" by the International Union for Conservation of Nature (IUCN). However, their populations have declined in some areas due to habitat loss and degradation, predation, and competition for nesting sites with invasive species. Providing nest boxes for Tree Swallows can help mitigate some of these threats and encourage their populations to thrive.

In conclusion, the Tree Swallow is a fascinating bird species that is easily identifiable by its iridescent blue-green feathers and white underparts. These birds are migratory cavity nesters that primarily feed on insects and are known for their aerial acrobatics and aggressive behavior. By providing nest boxes and protecting their habitats, we can help ensure the continued survival of this important bird species.