Tree swallows lay 4-6 white eggs in a feather-lined cup of grasses that they make inside the hole of a tree or in a nest box. The feathers, which are gathered chiefly by the males, help to insulate the nest from cold temperatures. Females incubate the eggs for about two weeks; both parents bring insects to the hatchlings. Fledging occurs about three weeks after the hatch. The great majority of tree swallows return to nest in the same area, sometimes even the same box or tree that they used the previous year.
The tree swallow’s East Coast range encompasses areas from Newfoundland down to Maryland. They winter typically in the Carolinas and the Gulf Coast. In the fall, they gather in very large flocks along the coast where they “circle in big eddies like leaves caught in a whirlwind,” according to the Audubon Society’s Field Guide. They are among the first birds to reappear in Connecticut in the spring.
The males are identified by the glossy blue-green on their back and the top of their head, with blackish wings and tail feathers. They have white neck, chest and abdomen feathers. The females, as so often the case with birds, are much less showy, the youngest ones being predominantly brown with just a few bright feathers.
Tree swallows eat mostly insects that they catch on the fly, usually a little less than 200 feet above ground, although they can occasionally take some from the ground or the water. They sometimes include spiders and small berries in their diet. They are called “income breeders’ as they breed based on food abundance.
Tree swallows have an average lifespan of 2.5 years but have been known to be as old as 12 years in prime habitats. Almost 80 percent of the hatchlings do not survive their first year, mostly because of cold weather reducing insect availability. Also, they are preyed upon by kestrels, magpies, owls, falcons, and hawks. In addition, they suffer from the clearing of forests in their breeding areas and the reduction of marshes in their wintering areas, and they compete for nest sites with starlings, house sparrows and bluebirds. Despite all these difficulties, the tree swallows are doing well enough to not be included on the endangered species list.
Text by Friend of Holcomb Farm Shirley Murtha
Photo by Friend of Holcomb Farm Don Shaw, Jr.
