ANIMAL ESTATE client 1.04: PURPLE MARTIN
FROM ANIMAL ESTATES 1.0: NEW YORK
SCIENTIFIC NAME: Progne subis
ANIMAL PROFILE:
RANGE: The Purple Martin can be found throughout nearly the entire United States east of the Rocky Mountains. Although declining in many western states, it is also found in isolated areas in Canada, Oregon, Washington, California, Utah, Colorado, Arizona, New Mexico and Mexico. The bird is an early spring migrant returning from its winter grounds in South America.(National Geographic 1999)
HABITAT: Generally, Purple Martins inhabit open areas and prefer an open water source nearby. Martins adapt well in and around people, but are out competed by starlings and sparrows in urban areas. The birds like open spaces to maximize the effectiveness of their incredible flying ability. Having water nearby helps support plentiful insects for food.(PMCA 2001)
COMMUNITY:
HOME CONSTRUCTION: 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.
BUILDING MATERIALS: Grass, twigs, and mud. 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.
BUILDING MOTIVATION: The pair bond is monogamous and both parents build the nest out of grass, twigs and mud. Average clutch size is two to seven eggs and the female incubates them for fifteen days. Both parents feed the young for about one month. The young remain dependent for a few more weeks after fledging during which time they learn to forage by following the parents.
THREATS: Populations of Purple Martins have declined in many areas for two main reasons. One is the reduction of natural cavities due to logging and snag cutting. Not only does the Purple Martin {Progne subis} have food-seeking predators to watch out for, it also has to contend with two enemies that aren't even out looking for a meal but are just trying to steal the nesting sites from the martins. The two birds that have been most detrimental to the existence of the martin are the European starling and the English house sparrow.
Unlike the purple martin, which is native to North America, both starlings and house sparrows are species that were introduced to North America. Some pairs of each were brought over to the United States from England in the late 1800's, and their numbers have increased dramatically ever since. At the same time the martin population, like that of other native cavity-nesting birds here, has drastically decreased. This is not a coincidence; the declining numbers of our native bird species are directly related to the population explosion of the European starling and the English house sparrow. Note: The English house "sparrow" is not really a sparrow at all; it's actually a weaver finch.
Each fall the purple martin migrates to South America and returns to the United States and Canada the following spring. Starlings and house sparrows, on the other hand, stay in their territory year-round. As if the arduous flight back from South America doesn't already take a big enough toll on the martins, upon their return in the spring, they often find that much of the existing housing has already been claimed by these two foreign species and are usually forced to try to find a nesting site elsewhere. Even if a martin pair does manage to find an empty cavity in which to raise a family and is fortunate enough to reach the egg-laying stage, the martins' efforts oftentimes end in failure because of the presence of their two bird enemies.
If starlings have already taken over a martin house, they will chase off any investigating martins. If martins are able to start nesting before any starlings show up at the colony, that doesn't mean that the starlings will leave the martins alone. When the martin pair is out foraging for insects, starlings will enter the cavity and destroy any eggs or nestlings found there. Upon their return, the martins will be chased off by the starlings. If a starling can trap an adult martin inside the compartment, the martin doesn't stand a chance against the sharp, powerful beak of its adversary. The starling will inflict mortal wounds on the martin. Once the starlings have the martins out of the way, they will proceed to build a nest, sometimes right on top of the eggs or young, and use the cavity to raise their own brood.
European starlings are deadly enemies of the purple martin, but English house sparrows can wreak their own havoc on a martin colony. They also investigate a martin colony intent on propagating their kind and will fill nesting compartments so full of nesting materials that martins will be unable to enter them. Very often the owner/landlord of a colony may see both martins and sparrows nesting in a martin house and be under the mistaken assumption that the two species are co-existing peacefully. Reality, though, is that the sparrows will go from compartment to compartment pecking holes in the eggs of the nesting martin pairs. This accomplishes the sparrows' goal, which is to prevent the martins from raising young, thereby reducing their future competition. Martins will abandon the colony after that, because it wouldn't be in their best interest to stay at a site where they had nest failure. Unfortunately, starlings and house sparrows don't limit their aggression solely to martins but direct it toward all of our other native cavity-nesting birds as well. source: purplemartin.net
INTERESTING FACTS: Purple Martins only eat flying insects that they catch while in flight.
MAKING A PURPLE MARTIN HOME:
REFERENCES: link 01 / link 02 / link 03
Thomson, M. 2001. "Progne subis" (On-line), Animal Diversity Web. Accessed November 09, 2007 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Progne_subis.html .
Coates Manufacturing, "Purple Martin Information" (On-line). Accessed 10/22/00 at http://coatesmfg.com/info.html .
Copley, D., J. Finlay, D. Fraser. 1999. Purple Martins, *Progne subis*: A British Columbian Success Story. Canadian Field-Naturalist : 226-229.
Davis, J., C. Brown. November 1999. Costs of coloniality and the effect of colony size on reproductive success in Purple Martins. The Condor , 101: 737-745.
National Geographic Society, 1999. Field Guide to the Birds of North America Third Edition . Washington, D.C.: National Geographic.
Purple Martin Conservation Association (PMCA), 2001. "Attracting and Managing Purple Martins" (On-line). Accessed 10/22/00 at http://www.purplemartin.org/main/mgt.html .
Russell, K., S. Gauthreaux. September 1999. Spatial and temporal dynamics of a Purple Martin pre-migratory roost. The Wilson Bulletin , 111: 354-362.
ADDITIONAL RESOURCES:
Purple Martin Conservation Association