Tree Swallow (Tachycineta bicolor)
Place observed
Tylee Marsh, Miller Marsh and former golf course aera.
Description
Adult males and females have similar plumage: iridescent blue-green back and top of head, white throat and breast, and brown wings and tail. Females are a bit duller and sometimes more green. Their plumage matures more slowly than that of the males, which are also slightly larger. Juveniles are brown and white.
Habitat
This is the most common swallow species in North America. Its breeding range covers most of Canada and much of the United States. It frequents mainly open areas in freshwater wetlands but also fields and farmland.
Tree Swallows nest in cavities in dead trees dug by other birds and sometimes even in bluebird nest boxes. Each year, they return in large numbers to Tylee Marsh in Rosemère. A few have also been observed at the Miller Marsh and the former golf course.
In July-August until late in the fall, Tree Swallows begin a daytime migratory journey that will take them to Mexico, the southern coast of the United States, Cuba or the southern countries of Central America. To spend the night, they sometimes gather in hundreds or thousands of individuals.
Diet
It is a bird that feeds on insects, mainly those of the order Diptera: flies, mosquitoes, hoverflies, midges.
Reproduction
In general, males and females do not form the same couples every year. The female prepares the nest alone with twigs and the male sometimes adds a final touch by lining it with feathers from other birds.
The female lays 4 to 6 eggs and incubation lasts 14 to 15 days. Usually, the female has one or more of her eggs fertilized by other males in the area. Afterwards, the female and the male of the pair take care of the needs of the chicks which will be ready to leave the nest between the 16th and 22nd day.
Status and threats
Currently, the Tree Swallow is considered a species of least concern by the International Union for Conservation of Nature (IUCN). However, aerial insectivores are in steep decline and the number of individuals of this species has been constantly decreasing in Quebec for about 40 years (5% each year on average).
The causes are multiple: the fragmentation of natural environments, urban sprawl, intensive agricultural practices such as the control of insect pests which makes their feeding difficult, a limited ability of the species to adapt to the magnitude of climate variations that take place.
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