The limitations of their diet and foraging technique leave them at risk of starvation if bad weather persists for three days or more in a row. Heavy rain or cold temperatures are often lethal causing high casualties of Purple Martins. Reproduction Purple Martins are colonial nesters and are very dependent on man-made nest houses. Once established at a nest location, martins usually come back every year to the same site. The Purple Martin only nests in cavities, often in abandoned woodpecker holes, but today most of the birds use man-made nest boxes.
Martins are now entirely dependent on human supplied housing east of the Rockies.
Although birds in colonies face increased risk of parasites, and increased competition for resources, reproductive success is not highly dependent on colony size. Males compete for nest sites within the colony. Although there is a lot of physical contact during fights, birds are rarely injured severely. Females are also known to fight over nest sites. The larger the colony, the more the birds fight over territory.