Post by Jen Berlinghof
There’s solace to be found in the fact that the rhythms of nature march on. This spring, the sun still rises. The wild leek (Allium tricoccum) still pulses its verdant green arms through the pulpy leaf litter of the forest floor. The birds still surge through the skies as they migrate to and through the Lake County Forest Preserves in northern Illinois. Like us, some of these birds are inclined to congregate in large communities. Over the years, the colonies of a particular species, the purple martin (Progne subis), have become largely reliant on people to provide shelter for their nesting flocks.
Purple martins are the largest member of the swallow family, a group of birds known for their aerial acrobatics, swooping and swirling to nab flying insects in the open sky. Traveling up to 600 miles a day during migration, purple martins typically arrive in Lake County around April 1 each spring after spending the winter in South America. Older birds called “scouts” appear first, returning to areas where they’ve nested previously. First-time breeders follow a few weeks later.
Historically, purple martins nested in natural cavities, from tree holes to rock crevices. Over time, non-native species such as house sparrows (Passer domesticus) and European starlings (Sturnus vulgaris) have pushed them out of these spaces. These evictions, coupled with the rise in popularity of humans erecting houses for them, has led to a majority of purple martins nesting almost exclusively near cities and towns in these miniature condos throughout the eastern U.S.
Our desire to observe the behaviors of these birds and provide refuge by putting up martin homes near our own is not a new trend. Native peoples hung up hollowed-out gourds to attract colonies. Martin houses became so common in the early 19th century that John James Audubon, the famed ornithologist, used them to help choose his lodgings each night. “Almost every country tavern has a martin box on the upper part of its sign-board, and I have observed that the handsomer the box, the better does the inn generally prove to be,” he wrote in Birds of America, his landmark collection of 435 bird prints.
These abodes are so important that females choose a mate largely based on the nest site he occupies. The nest hole is filled with twigs, plant stems, mud, and grass acquired on the adult birds’ rare encounters with the ground. Each nest supports three to six eggs that hatch about two weeks after being laid. Hatchlings are ready to fly within a month. Purple martins are known for their hallmark quick flaps and long glides, eating all of their insect food in flight. They even drink water on the wing, skimming the surface of a pond and scooping up water with their lower bills.
Purple martins soar to altitudes higher than other swallows, averaging 150 feet off the ground and climbing upwards of 500 feet in pursuit of prey. They’ve been observed turning suddenly sideways or upwards, accelerating and flaring their tail feathers wide to ensnare insects. Their main targets are mostly large: dragonflies, beetles, leafhoppers, crickets, cicadas, moths, and butterflies. While it would be wonderful if this “bird of the people” was a connoisseur of mosquitos, that myth has been dispelled. It seems the only small items this bird ingests are bits of gravel to help aid the digestion of all those exoskeletons.
Toward the tail end of summer, purple martins start to gather in large flocks to roost together in preparation for migration. They form such dense groups to feed, rest, and socialize that they can be seen easily on weather radar. Want to witness the hordes firsthand? Project MartinRoost tracks reports of the gatherings. After migrating to South America for the winter, martins assemble in roosts there, often around manmade structures. This has created issues explored by The Life of Birds documentary series.
Once spring arrives, the birds push north again. As Emily Dickinson famously wrote, “‘Hope’ is the thing with feathers.” May you find comfort in the way nature—and birds—carry on this spring. And may you find hope in the purple martins who arrive home to have and raise their young.