Purple Martin Project
About The Colony
Lying on the gently rolling, grass-covered slope just north of Lake Arnold at Blandy Experimental Farm, Shenandoah Audubon hosts the Purple Martin Colony Project to provide suitable nesting habitat and to educate the public about Purple Martins. This nesting colony site is home to North America’s largest swallow, the Purple Martin (Progne subis), generally referred to by birders as “PUMA” (the Institute for Bird Population's alpha code).
Being neotropical migratory birds, cavity-nesting Martins return each spring to this location around mid-April from South America to build their nests and raise their young. The older Martins are first to return to their previous nesting sites, followed several weeks later by individuals that hatched the year before and are making their first trip back.
Shenandoah Audubon funds and maintains the Purple Martin Colony through gifts from Chapter members and private citizens as well as an annual donation from The National Audubon Society. The colony is currently maintained by PUMA Landlords Ted Saunders and Kaycee Lichliter.
The Purple Martin Colony is located in an open area away from buildings and trees to match the birds' nesting habits. The housing units are mounted on telescoping poles 10 to 20 feet above the ground for once a year cleaning with limited data collection; otherwise, the houses are not monitored during the nesting season.
The colony includes eight (8) Silver Series Deluxe Gourd Rack. Each rack includes 12 units (PUMA Excluder Gourds) with polyester rope and 4-part pulley systems along with stainless steel predator guards, top perch rods and Starling-resistant entrance holes.
When identifying PUMA from a distance, look for the dipping and diving, swiftly flying swallow with the broad chest, a short, forked tail and long tapered wings. What can you notice by taking a closer look?
Males: Adult males are the only Purple Martins to have their entire body covered with iridescent, purple feathers, but this only sets them apart beginning in their third calendar year. The subadult males, males younger than third year, but not those hatched during the current year, are often the hardest to identify. They will have at least one, sometimes many, solid-purple feathers either on their chins, throats, bellies or undertails (the group of feathers under their tails also known as ‘undertail covs”).
Females: The adult females do not have purple feathers on their chest, belly or undertail covs and will have more purple on their heads and backs and their undertail covs will be dark. The subadult females, have lighter purple to brownish colored feathers on their backs with undertail covs that are all white or light colored with brown pinstripes down the center.
Young: A hatchling or juvenile bird, one hatched in the current year, cannot be determined male from female by sight, but they will have short stubby tails with white undertail covs, a dull brownish-gray color on their backs and heads, and the sides of their immature beaks will be bright yellow (referred to by birders as “bird lips”).
Identification can be quite tricky, especially when the Martins keep moving, diving and circling overhead, but do not let that frustrate you; just sit back and enjoy their chattering and acrobatic display.
Nests, Eggs, and Hatchlings
The male Purple Martin chooses the nesting site and the female chooses her mate based on the nest site he occupies. Purple Martin nests are made of twigs, plant stems, mud and grass. They lay 3 to 6 eggs per clutch with one, possibly two, broods per season. The eggs are pure white in color and smooth, measuring roughly 1 inch x 0.8 inch. The pair incubates their eggs for 15 to 18 days. The eggs hatch, producing weak and completely bare pink-skinned hatchlings, which require a 27 to 36-days growth period before they are old enough to maintain flight and leave the nest.
Purple Martins are aerial insectivores, feeding during the daytime while in flight. They consume vast quantities of insects, including but not limited to butterflies, moths, flies, dragonflies, damselflies, leafhoppers, grasshoppers, crickets, wasps and bees. Martins feed high in the sky and can be vulnerable to starvation during prolonged periods of rain and cool weather due to limited access to flying insects during these periods.
Two competitors at Purple Martin Colony nesting sites are European Starlings (Sturnus vulgaris) and House Sparrows (Passer domesticus); both are non native invasive species in North America. Neither species is protected by the Migratory Bird Treaty Act, a United States federal law first enacted in 1916. Both species are known to take over Martin housing, destroy Martin eggs and kill Martin adults and nestlings.
To prevent the invasive species from taking over Colony sites during the winter/early spring months before the PUMA return to the site in the spring, it is recommended that the housing units or gourd entry holes be closed until the first returning PUMA have reentered the area. Housing units at the Shenandoah Audubon/Blandy Experimental Farm Colony site are protected by 8-inch diameter, 24-inch long stainless steel or aluminum stove-pipe baffles or by circular cone guards to prevent access by ground-dwelling predators.