A colony of white, gourd-like houses hang on a large pole outside of the Dickinson County Nature Center.
Around them flies dozens of gliding, floating, flitting dark birds — purple martins. Local birder and owner of Bird Haven in Spirit Lake Wendell Hansen has cared for the purple martins for many years, and last June he reported that there were about 20 nests with 109 eggs and young.
Purple martins are neat creatures, with their iridescent purple coloring, so let’s take a look at some fun facts about the largest swallows in the U.S.
1. Purple martins like gourds.
The reason purple martin houses still are often shaped like gourds goes back to a time before Europeans inhabited North America. Native Americans hung up empty gourds for the swallows to nest in, and people still hang up hollowed-out gourds for bird houses. Purple martins will also nest in tree cavities, woodpecker holes, on cliffs, in birdhouses or even in saguaro cactus in the southwest.
In the eastern U.S., the subspecies of purple martins completing went through a tradition shift to using exclusively man-made homes. Only three North American birds species have transitioned to only using man-made nesting structures to nest in or on: Eastern purple martins, chimney swifts and barn swallows.
2. They are high-flying feeders.
You’ve probably never seen a purple martin at your bird feeders. That is because they are year-round insectivores, and they catch flying insects at heights of 150-500 feet off of the ground. They will swerve upward or sideways, speed up and flare their tails to trap beetles, flies, dragonflies, damselflies, butterflies, bees, cicadas and more. Like other birds, they also pick up pieces of gravel to help them digest.
3. Purple martins aren’t actually purple.
Adult male purple martins get their iridescent feathers, which can appear blue, purple and even green, when they are about three years old. Before that, males have some solid-purple feathers as well as a mottled white and gray feathers on their bellies, chins and wings. Subadult males can get confused with adult females, who also have some purple on the head and back, but they will not have any purple feathers on their chest, belly or undertail. Subadult females have even fewer purple feathers.
You can identify a hatchling, because it will have a tail that is shorter than its wing feathers.
4. The birds in our nesting colony may be many of the same ones as last year.
The first purple martins that arrive back each spring are called scouts, and they are the oldest birds that return to the nesting site from the previous year. About a month after those adults arrive, the subadults that fledged the previous year return, and nest building begins about a month after that.
Purple martins return to northwest Iowa in mid-April typically.
5. Purple martins have plenty of competitors.
Purple martins have many competitors for nesting, and many of their man-made nesting structures have been designed to keep out some of their competitors. Purple martins compete for space with eastern bluebirds, tree swallows, house wrens, and great-crested flycatchers as well as with non-native European starlings and house sparrows.
6. They are large and in charge.
Purple martins are the largest swallow in the U.S. with a length of 7-8 inches and wingspan of up to 15 inches, and they are also among the world’s largest of approximately 90 swallow and martin species.
7. They are good parents.
Purple martins are very good parents, feeding their chicks up to 60 times per day. Both the male and female will bring the chicks insects that are high in protein.