Males will often arrive early in the season to claim a particular nesting site and rigorously defend it from other males. Afterward, both sexes will often visit various house cavities before choosing the final location. Sometimes they may claim two compartments and rigorously defend them both from other martins. The cavity may be located in a birdhouse, gourd, dead tree, saguaro cactus, building, or cliff, but sometimes in other structures like traffic lights, street lamps, dock pilings, or oil pumps. Purple Martin birdhouses and gourds are either natural, made of wood or aluminum, and contain 8–12 rooms. Housing units can be hung from wires or sit atop poles in open areas and can be made to raise and lower.
Ontario’s martins usually nest in birdhouses provided by humans. Seldom do they nest in woodpecker holes in trees since their numbers are severely in decline. Nests usually contain twigs, plant stems, mud, bean straw, grass, or pine straw.
Eggs and Young
Clutch Size: 3-6 eggs
Number of Broods: Usually 1 brood
Egg Length: 0.8-1.1 in (2.1-2.7 cm)
Egg Width: 0.6-0.8 in (1.6-1.9 cm)
Incubation Period: 15-18 days
Nestling Period: 27-36 days
Egg Description: Pure white and smooth.
Condition at Hatching: Weak, with completely bare pink skin.