The Ever-Popular Purple Martin
One reason the purple martin is so valued by birders is its hungry appetite for flying insects. With a diet comprised almost exclusively of insects, one purple martin can eat as many as 400 flies in a single day.
To encourage the purple martin to nest in your yard, you should have proper nest boxes erected and available for the first scout that arrives each spring, usually from mid-February in Florida to early May in northern states. Purple martins will nest in two types of nest boxes-gourds and traditional nest boxes. Gourds, whether natural or man-made, are a good choice since they swing, which inhibits competitors like starlings or sparrow from attempting to nest in them.
Locate nest boxes 12-15 feet in the air, approximately 100 feet from any structures or trees, but close to human activity. Be sure to repeatedly clean out old nests. If you capped the holes last winter, be sure to uncap a hole once you spot the first martin scout of the spring. As more martins arrive you can uncap the rest of the entrance holes.
Are you one of many house owners who are frustrated by the fact that you're unable to attract breeding martins to your site? Ask yourself the following questions. Your answers may help you discover the reason why you're not attracting these wonderful heralds of spring.
Eight Questions to Ask Yourself about your Martin House
- Is your housing placed too close to tall trees or in a yard that is too enclosed?
Martins have very specific aerial space requirements. The air space immediately surrounding their housing, at the height of the housing, should be unobstructed in at least a couple of directions so the martins can fly to and from their housing in nearly level flight. There should be no trees taller than the martin house within 40 to 60 feet.
- Is your housing placed too far from human housing?
Martin housing placed more than 100 feet from human housing has a lower chance of being occupied. This is because martins have learned through natural selection that the closer they nest to man, the safer they are from their predators. Martin housing should be placed in the center of the most open spot available, 30 to 100 feet from human housing.
- Is your martin house white?
Martins are attracted best to white houses. This may because housing painted white reflects the heat and white highlights the darkness of the entrance holes, making them more conspicuous to searching martins. Also white is believed to enhance the male martin's courtship display.
- Do you keep other species out of the house?
If any other species is allowed to settle into a martin house at unestablished sites, those houses will rarely attract nesting martins. Birds set up territories around their nest sites and defend them against other birds. Previous nesters will repel martins that search for nesting sites. If the martin has never nested at a particular site, they are easily repelled. On the other hand, if a martin has nested at a particular site, it will rarely be intimidated from reoccupying that site the following year. Repeatedly cleaning out the nests of other species is required. Cap your house until other species have accepted new housing, then reopen for the martins.
- When do you open your house?
Migrating martins arrive in a continuing process for eight to 12 weeks in the northern range and 12 to 16 weeks in the southern range. The oldest martins arrive first, the youngest ones last. Martins generally return to the exact site where they've bred the previous year. Sub adult martins, the ones attracted to new sites, usually begin returning to any given area about four to five weeks after the "scouts" (those who return early). Opening a nest too early will result in instant occupancy by competitors.
- Is your house built to specifications?
Some published plans and a few commercially built houses are drawn or made to improper dimensions. According to the Purple Martin Conservation Association, a purple martin house must have compartments whose floor dimensions measure at least six inches by six inches. The entrance hole should be placed about one inch above the floor and have a diameter in the range of two to two and a quarter inches.
- Can you manage your martin house properly?
Your martin housing needs to allow for easy raising and lowering with compartment access. Martin housing should be mounted on poles that telescope up and down or raise and lower with a pulley and winch system. Don't be afraid to lower your houses often to check on your martins. Such disturbance will not cause martins to abandon their nests or their colony site. Number the compartments and keep records of what is going on in your house.
- Do you have vines or shrubs growing under your martin house?
Houses with tall bushes growing around the base of the pole or vines growing up the pole will rarely attract breading martins. Martins tend to avoid such housing as it is much more accessible to predators such as cats, raccoons, and squirrels.
Reference: Bird Talk 1996