Ontario Conservation Status and Longevity
Ontario Conservation Status
Ontario’s Purple Martins are fairly common birds, especially in southwest Ontario, but their numbers have declined by approximately 0.5% per year, resulting in a cumulative decline of about 25% between 1966 and 2019, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 9.3 million and rates them 10 out of 20 on the Continental Concern Score, indicating a species of relatively low conservation concern. Humans have helped counteract declines somewhat by putting up nest boxes, and people now provide virtually all nest sites for Purple Martins in the eastern U.S. yet Eastern Purple Martins are still in decline in Eastern Canada. Introduced species such as European Starlings and House Sparrows often take over martin houses and injure or kill eggs and nestlings. Purple martins compete with these invasive House Sparrows and European starlings for nesting sites. (Brown, 1997; Fraser, et al., 1997)
Purple Martins are also sensitive to cold snaps; bad weather kills more birds than all other sources of mortality combined. When unseasonably cold temperatures last more than three or four days, the birds starve for lack of insects. In the western U.S., logging practices that remove dead trees can reduce nesting habitat for martins. Reduction of pesticide use on their South American wintering grounds and protection of large winter roosts in Brazil is also important to the conservation of this species.
The longevity of purple martins ranges from 0 to 13 years and nine months. Purple martin mortality is often the result of severe weather. Three to four days of severe weather can lead to insect numbers drastically declining. If there is a lack of food, purple martins cannot survive and this often results in population decline. Another hindrance to long life expectancy is often body parasites. A protozoan blood parasite Haemoproteus progeny can have disastrous effects on the survival rate of first-year birds during the winter and migration period. (Brown, 1997; Layton, 1972)