Top Ten Mistakes with Purple Martins

by Richard A. Wolinski
and James R. Hill, III

There are thousands of martin houses put up throughout the continent that simply never had a chance of attracting purple martins in the first place. This has added to the mystique of attracting martins. The following are ten common mistakes landlords make that cause their colonies to be martinless. With this information we hope to tip the odds of attracting martins in your favor.

10. Housing placed in an inappropriate location

Martin housing is placed in yards without sufficient open space. Trees, buildings, or other objects that prevent easy aerial access to the martin house make the location unsuitable. Martins tend to fly into the colony on a level flight path; if this is not available from several directions, the location is too closed in for easy access. Select a site with a minimum distance of 40 feet--more if possible--from the nearest tall tree and place the housing in the center of the open spot. If the location barely meets this requirement try to place the house at a higher elevation or remove trees to provide better martin habitat.

9. Nest site competitors established in house

To attract martins to a new location-one at which they have never nested before-the housing must not be occupied by another bird species. If house sparrows, starlings, eastern bluebirds, great-crested flycatchers, or tree swallows lay claim to the house first, martins will be driven away even though empty cavities exist. Without a previous nesting history at the site (nest-site tenacity), the martin will look elsewhere for a suitable nesting site (see "Competitors").

8. Martin house placed too far away from human activity

Houses are often placed in open fields, pastures, or next to farm ponds at quite some distance from human housing. These sites are seldom used. Placing martin housing from 40 to 100 feet away from your house is quite acceptable to the martins and tends to offer predators less opportunity. The martins' long association with humans has influenced their selection of nest sites based upon physical distance and the likelihood that humans will repel any predators they see near the colony.

7. Housing opened too early. At unestablished colony
locations this is a key reason for failure

Most potential landlords are eager to get the martin housing up and ready for any passing martins that may be in the area. This would work if fully adult martins were the birds responsible for starting new colonies. But most often it is the younger, subadult birds-those hatched the previous year-that move into new locations, and their arrival is from four to five weeks later than that of the scouts. Opening the housing up this early offers greater opportunity to resident nest-site competitors. Check the usual arrival date for martins in your area and watch for those first arrivals; then plan to open the housing about four weeks after this date. Martin migration takes place over a considerable span of time, and new birds are passing through all of the time. If your house is open and without nest-site competitors, your chances of drawing and holding birds is increased substantially. There is one possible exception to this rule. You have a slight chance of attracting full-adult martins early on if you have an excellent colony site and if you have another active colony within about a mile.

6. Housing kept closed too long

The flip-side of opening housing too early is that often those who are trying to attract martins for the first time keep ALL of the compartments closed up until they see the first martins at the house. At unestablished colony locations it is not possible to hold martins even briefly if they do not see at least one open cavity available for their use. They need to see into a cavity or to see or hear other martins at the location if it is to be attractive to them at all. The solution is to keep at least one entrance open on each side of the house for inspection by the birds when they arrive at the site. This minimizes the number of compartments that would be available to nest site competitors. Veteran landlords with established colonies can leave their compartments completely closed until the martins return. Because of their strong nest-site tenacity the martins will wait a short while until the compartments are opened up for their use by the landlord.

5. Housing not painted white

After so many years of being attracted to white martin houses and white-painted gourds, martins seem especially to favor white housing. White paint (oil-based paint is best) has some practical usefulness as well; it helps reflect heat from the house and serves to protect wooden houses and gourds from the elements, extending their useful lifetime. Trim color can be varied as long as the majority of the house is white. There may also be behavioral reasons why white houses are selected by martins. White offers a strong contrast with the dark opening of the cavity (and by extension, a strong stimulus as a potential nest site), and the male martin's courtship display may be enhanced by being shown off against a light background color.

4. Plantings located at base of martin houses

Martins are sensitive to the possible presence of predators near the colony, and they seem to sense that vegetation can conceal a predator directly below the nest site itself. Don't plant at the base of the pole if you are starting a new colony. Remove such plantings from around unoccupied housing if it appears the site would otherwise attract martins. If this fails, relocate the house to a more suitable location.

3. House design is unsuitable for use

There are a great many places to look for martin house plans: state wildlife agencies, popular bird books, and in martin publications. But published plans are often inaccurate in the dimensions of individual nesting compartments. Some commercially available housing is also not suitable, based upon these criteria. Scientific studies conducted in recent years suggest the following: Floor dimensions should be a minimum of 6" x 6" (6 inches wide by 6 inches deep), though larger is better (7" x 12" is excellent); the entrance hole should be 2" to 21/4" in diameter and placed so that the bottom of the entrance hole is 1 inch above the floor. Martins will use entrance holes down to 13/4" in diameter if the other dimensions are acceptable. If your housing does not meet the minimum requirements it should be modified or replaced by more acceptable housing.

2. Housing too close to or attached to wires

Housing that is placed within leaping distance of utility wires or that has wires attached to it from a house, garage, trees, or other objects is unacceptable to martins. Martins tend to avoid situations that would allow a squirrel or another mammal access to the house by jumping or crawling from an elevated position.

1. Housing that cannot be easily managed by landlords

Often one of the last things a potential landlord learns about is how important it is to be able to get into the martin house to clean or manage the colony. Housing that cannot be erected or taken down easily by lowering it from the pole vertically with a telescoping pole or pulley-and-winch system (as opposed to a swing-down pole), and which fails to offer easy access to individual compartments, soon becomes a burden to the landlord. A direct result of this is a decrease in active colony management. Keeping the house clear of nest site competitors and checking nests are important activities that contribute to raising more young martins each year. Ease of access is one of the most important considerations in selecting an appropriate house design, whether you are building a martin house or are considering the purchase of a commercially built martin house system.

Reprinted with permissions from Bird Watcher's Digest
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