The Nature Writers of Texas

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Thursday, March 20, 2008

Purple Martins vs. Red-shouldered Hawks
by Ro Wauer


Neighbors have wondered why I have not reinstalled my martin house. It has been a spring staple in my community for the last dozen or so years. I have religiously set up my martin house in my yard in early March, and within a few days purple martins begin checking it out. And every year one or a few pairs of martins claim an empty site and begins their nesting process. But during each of the last four years that process have been interrupted by predation. My martin house has not produced a single youngster.

The purple martin predator each year has not been one of the more “normal” predators, such as a snake or raccoon. No, my purple martins have been decimated by a pair of red-shouldered hawks. These much larger predators land on the martin house, reach inside and extract the nestlings, and haul them off to their own waiting youngsters. But this year I have decided not to give them that opportunity by not reinstalling the martin house at all. Maybe by next year they will have forgotten about their source of martin morsels and ignore the martin house altogether.

The question obviously arises about which one of the two bird species would I prefer, purple martins or red-shouldered hawks. And that question is impossible to answer. After all, purple martins truly depend on us humans supplying them nesting sites, while red-shouldered hawks are totally independent, nesting high in trees where the nests are seldom readily visible from the ground. While red-shouldered hawks are full time residents in our neighborhoods, purple martins are neotropical migrants that are with us only during a few weeks in spring and early summer. They usually leave for their wintering grounds in Brazil by late July. In a sense, martins are more a South American species than a North American species, spending seven or eight months in South America and only four of five months in North America.

With mixed feeling, I have decided to forsake my martin colony this year. I can only hope that when next year rolls around and I reinstall my martin house that my red-shouldered hawks have found another diversion. But I won’t bet good money on it. Predators are opportunists, and I suspect that even this year’s youngsters will discover a fresh source of prey next year.

However, for my many readers that are still housing purple martins and are not experiencing the same kind of problems, if you have not already put up you martin house, it is time! And as a reminder, here are some easy rules to follow: (1) Houses must contain apartments with at least a 6x6-inch floor space and an entrance hole 1 ¾ inch in diameter and 1 inch above the floor. (2) Houses must be placed on poles 12 to 20 feet above the ground and should be 40 feet away from taller trees, poles, and other structures. (3) Poles must be free of vines and shrubs that might allow access to the house by predators. (4) Houses must be free of nesting materials and other debris that accumulated in the off-season.

Purple martins often are rather finicky at the start but seem to put up with shorter poles and poorly maintained structures once the colony is established. Most birds are repeats, but the majority of the first-year birds (usually last year’s youngsters) seek out new sites, usually in the general area of their natal home sites. This means that a new martin house, especially if it is in proximity of an active martin house, is likely to be used early on. Distant houses are not as likely to be selected.

Housing purple martins is not only fun, but a fascinating connection to the outdoors and to our interrelationship with the tropics. Good luck!

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