Purple Martin

Progne subis

Many of you may have noticed the strange looking pole full of plastic gourds that went up this last month at both Ridgefield and Steigerwald Lake National Wildlife Refuges. These gourds are specifically for housing Purple Martins.

We are lucky to see them at all on the West Coast, as they are much more common on the East side of the country, especially the Southeast. A majority of them migrate primarily to the Gulf Coast in the late summer through the winter. They travel long distances (up to 5000 miles each way, each year) at a leisurely pace – flying only during the day and foraging as they go. Their wintering grounds are savannas and agricultural fields in Bolivia, Brazil, and elsewhere in South America. At night, wintering martins flock into cities and towns to roost, often in the trees of village plazas.

Purple Martins have a fairly healthy population and are not listed on any watch-lists currently, but they have experienced decline, with a 1% population drop every year between 1966 and 2015, resulting in a total of a 37% decline, according to the North American Breeding Bird Survey. Luckily, in this case, humans have helped forestall that decline a bit by putting up nesting boxes and hanging gourds like the ones on the Refuge. Humans account for almost all of the nest sites for Purple Martins in the East, and here on the West side, they have found more opportunities for natural nesting cavities, but still rely heavily on man-made nest boxes and gourds.

Purple Martins live up to their name, with the males sporting iridescent dark blue-purple plumage and black-brown wings and tail. Female Purple Martins are duller, with more grey on their head and chest, and a grey ring around their neck. In flight, you can identify them along with other swallow species by their tapered wings and forked tail. The adult males will look almost black flying high above the other swallows, catching insects from the air. Martins tend to fly higher up above other swallows during the day, coming down lower in the evening. The Purple Martin gets all its food in flight, and it gets all its water that way too. It skims the surface of a pond and scoops up the water with its lower bill. They almost never land on the ground except to pick up nesting material and small bits of gravel, as grit to help them digest the exoskeletons of the insects they eat. If you know you have purple martins nearby, you can put out crushed egg shells for them, as a source of grit.

They are year-round insectivores, and as such are sensitive to cold snaps, where if it is cold for more than three or four days, the lack of insects could lead them to starve. European Starlings and House Sparrows are their number one enemy, and often raid and destroy martin nests. This can be prevented by hanging the gourds made specifically for them, which have a smaller opening that the larger birds can’t penetrate, or by putting up guards on nest boxes to prevent starlings and sparrows from entering the nest.

Purple Martins lay up to six white eggs, laying a single egg per day until each egg is laid. The eggs are incubated for about 15 days, and the babies fledge for 25-35 days after they hatch. Martins pair up with one male and one female per nest, but sometimes two females may settle into different compartments of one male’s territory. Both sexes frequently mate outside of their pair bond. Adults form flocks as soon as nestlings fledge, and congregate in large roosts throughout the winter.

You may have noticed in our “From the Contact Station” article, Susan mentions that a single test gourd is put up a few weeks before the rest are hung. These are set up for the “scouts” which are the earliest martins to arrive in the season. These scouts are the oldest members of the population, which are returning to where they were hatched. Scouts can be both male and female, and signal the arrival of the rest of the flock, usually about two weeks behind.

Did you know? Putting up martin houses used to be so common that John James Audubon used them to choose where he would stay for the night. In John James Audubon’s Birds of America, plate 22, he notes, “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.”

Native Americans hung up empty gourds for the Purple Martin before Europeans arrived in North America.

-Samantha Zeiner, Friends of Ridgefield National Wildlife Refuge
Photos by: Lane Sample