Purple Martin bird houses were first used to attract breeding pairs of Purple Martins by Native Americans. They would hang hollowed out gourds from trees to encourage nesting. No one really knows when this practice began, but it is believed that it was done to aid the Native Americans with pest control.
Mating pairs would protect their Purple Martin bird houses from predators like crows and hawks and in turn protecting the Native Americans' food crops.
Another advantage to having Purple Martins around was that they ate large amounts of flying insects. The Native Americans quickly learned that the more gourds they hung, the fewer flying insects there were.
The Purple Martins began to breed more often in the artificial Purple Martin bird houses and less in the natural cavities they had been using. Today, Purple Martins in the eastern area of North America are totally dependent on martin bird houses for breeding.
Purple Martin bird houses are available in wood, plastic and metal. Natural and plastic gourds are also used as Purple Martin houses. Unfortunately, not all commercially produced martin bird houses are properly designed to protect a colony of Purple Martins.
Since Purple Martins are entirely dependent on nesting sights provided by humans, it is important that the housing used for nesting meet a few minimum requirements.
Martin houses should have easy accessibility for nest checks and general maintenance. Climbing ladders is not safe and tilting houses do not work well. You need to have a system that allows for the house to be lowered and raised vertically.
The size of the nesting compartment is very important. Each compartment should be a minimum of 6" wide x 5 ½" high and 9" deep. Larger is always better, but any thing smaller is inadequate. A nesting compartment at least 9” deep will allow the family of Purple Martins to escape the reach of flying predators like owls.
Martin bird houses should be white (including gourds).Research has shown that white houses remain 10 to 15 degrees cooler than dark colored ones. Houses that are over heated may cause fledglings to leave the nest before they are ready in order to escape the heat.
Nesting compartments should be easily accessible. Hinged or removable panels work the best. As a landlord you will have to clean out old nests, perform nest checks, control insect pests, remove unwanted pest birds and perform general maintenance.
Proper ventilation is a necessity. Several ½" diameter holes near the top of the compartments will provide ample airflow. This feature is especially important in the southern breeding regions. Reducing heat in the nesting compartments will greatly increase the young birds' chances of survival.
Starling Resistant Entrance Holes (SREH's) are very important to the survival of the Purple Martin family. Many martin houses come equipped with SREH's, but if your house does not, there are adapters available. There are several styles of SREH's but the height should be exactly 1 3/16" high. This is critical because any higher and European Starlings will be able to get in and any smaller and Purple Martins won't be able to get in.
Recent studies have provided information showing that porches inside and outside the compartment are very beneficial. The porches should be a minimum of 3" x 3". They should be placed no more than 1/8" below the bottom of the crescent shaped opening. These porches help the Purple Martins negotiate these tighter openings while making it harder for European Starlings to get inside.
Purple Martins have many predators but the European Starlings have done the most damage to their population. European Starlings were introduced into the U.S. in the 1800's. The problem is that the starlings take over the nesting sites of Purple Martins. They are very aggressive nesters to the point that they will kill nesting Purple Martins to take over the nesting spot. Since martins only raise one brood per year this is devastating to population levels. If you have starlings nesting in your martin bird houses they must be removed. House sparrows are another problem bird not native to the U.S. They also have to be removed when found in martin bird houses.
Once you decide you are ready to support a Purple Martin colony you need to determine the best location. Purple Martin bird houses should be placed as far away from trees as possible. A good rule of thumb is your martin bird house should be as far away from a tree as the tree is tall. So if a tree is 50 feet tall then the house should be placed at least 50 feet from that tree. Tall trees provide hiding places for predators that feed on Purple Martins like hawks and owls. Martins are aware of this danger and will not nest in houses where they don’t feel safe. The more open the area is around the martin bird house the better chance you have at attracting a colony of Purple Martins.
Providing housing for a colony of Purple Martins is a big commitment. It requires you, as the landlord, to get involved. You will have to monitor the martin bird house for unwanted nesting competitors, complete regular nest inspections and keep the nesting compartments clean. Putting Purple Martin bird houses in your yard requires some work, but it is very worthwhile. These beautiful birds are fun to watch and are beneficial to our environment, but they do need our help for survival.
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