Open Field Birds, Pacific Northwest
Purple martins migrate from their wintering grounds to the south coast each spring to breed during the summer months and return back south in the fall. The western purple martins northern limit of their breeding range is the southern BC Coast. We have many of them that return each year.
The spring migration depends on age and gender, the adult birds are the first to arrive in Campbell River from early April to May to claim the best nesting sites. Younger birds arrive later in May and June and have to settle for less than perfect nesting sites. If all the nest boxes in the colony are occupied, young martins will head out and colonize a new nesting site. Purple martins build their nests in cavities. The purple martin traditionally used old woodpecker holes in snags, close to water. But most purple martins nest in man made boxes now. These nest boxes are usually clustered together on poles and pilings where the young birds are safe from most predators.
The female builds the nest in late May or June, with very little help from the male. Although the male will gather fresh leaves and cedar chips for the nest through out the incubation period and for a number of days after the eggs hatch. Nests can be made of what ever is at hand, twigs, grasses, wood chips, seaweeds and shells. They will line their nests with cedar chips and soft leaves to help keep down parasites. The female generally lays 4 to 5 eggs in June or early July, she will incubate them for 15 to 20 days. The female martin does most of the incubation with the use of a brood patch on her belly that transfers her body heat to the eggs.
The male martin does not have a brood patch but he will sit on the eggs for short periods of time to allow her to feed. Both the parents feed and care for the young after they hatch. In BC, young birds fledge about 4 weeks after hatching. Martins produce just one brood of young per year.
Our martins begin to fly south in early to mid August and most have left BC by the first week of September.