Once you have established a colony site, Purple Martins will usually return faithfully year after year, as long as they survive and breed successfully. Don’t take them for granted! When people lose all their martins from one year to the next, it’s almost always because of something preventable that happened right in their own backyard, often at night, while the martins were present. Small colony sites (2 or 3 breeding pairs) are especially at risk. Martins will only return if they successfully raise young.
The Six Biggest Reasons People Lose Their Purple Martins:
#1. Owl, Hawk, Raccoon, & Snake Predation. These are the martin’s four major predators. All four are good at locating Purple Martin colony sites. Raccoons and snakes can easily climb both wooden and metal poles to eat eggs, nestlings, and adults. But raccoons and snakes can easily be stopped by putting a climbing animal barrier on your pole. Owls and hawks can land on your housing and extract martins, scare them out, or snatch them right off of the porches. Most owls can be stopped by attaching owl & hawk guards; these barriers allow martins to slip through, while keeping owls and hawks at a safe distance from the entrance hole. Owls and raccoons are very abundant, even in the suburbs, but you won’t see them unless you sneak around your yard in the middle of the night! Don’t assume they’re “not around” because you’ve never seen them. All active martin housing should have climbing animal guards!
#2. Starling & House Sparrow Depredation. These two species are very destructive, aggressive and abundant. Do not allow them to nest in your martin housing! Starlings can actually kill adult Purple Martins. House Sparrows will break martin eggs and peck nestlings to death. Starlings and House Sparrows must be controlled. Luckily, starlings can now be excluded by using Starling Proof Entrance Holes. House Sparrows must, however, be rigorously controlled by trapping or shooting. Allowing these two pest species to nest among your martins will put your colony site at risk. For More about Starlings & House Sparrows, including photos, click HERE.
Extremes. Purple Martins are entirely dependent on flying insects
for food. When weather conditions become very bad, flying insects are not
active, and martins can literally starve to death after 4-5 days. Extended
periods of constant rain and cold temperatures are the most common type of
martin-killing weather. Tropical Storm Agnes killed almost all the Purple
Martins in southwestern PA in June of 1972. Martins
can be saved from starvation by throwing large crickets into the air for the
martins to catch, or by placing them directly onto the martin housing (porches).
For more information, and to view a video clip of this technique in action, go
#4. Nest Parasites. A certain number of mites, fleas, and blowflies in martin nests is normal. But, for a variety of reasons, parasites can sometimes become overly abundant, causing nestlings to die or parents to abandon them. These parasites (all harmless to humans) can be controlled by doing “nest replacements”. When nestlings are about 10 days old, remove the old, parasite-infested nest and replace it with a fresh dry bed of cedar shavings or soft, dried (brown) pine needles (White Pine, for example).
#5. Drastic Changes to Housing. People sometimes think that they're doing their martins a big favor by replacing their old dilapidated house with a brand new one during the off-season. Doing so may cause the martins to abandon the site, because they are very loyal to the housing they bred in the previous season. Never make drastic changes to the style or placement of your martin housing between seasons. Rather, place the new housing next to the old housing, and make sure some martins have bred successfully in the new housing for at least one season before removing the old housing.
#6. Tree Encroachment. Hawks use nearby trees to sneak up on purple martin colony sites and ambush martins. The closer the trees, the less time martins have to react and escape. When trees grow up around martin housing, it puts the martins at high risk by offering hawks a convenient and effective place to mount a successful attack. When trees are cut back or removed, martins usually have enough time to react and escape. Tree-encroached sites seem to be less attractive to martins that are looking for a place to breed. Since colonies maintain their numbers or grow by attracting martins that fledge from other sites, if "new recruits" cannot be attracted, a colony can dwindle away.
The Purple Martin Preservation Alliance (PMPA) is an all-volunteer organization dedicated to the conservation of Purple Martins through education, research, and conservation projects. Our Web Address: http://www.purple-martin.org Our e-mail address: firstname.lastname@example.org