The following article was written by Raymie Miller, a summer intern at the Woodland Dunes Nature Center.
Nearly every day while working here at Woodland Dunes, I hear a distinctive twittering chatter from high above. This is the sound of the Purple Martin, the largest species of swallow. Purple Martins feed high in the air, higher than other swallow species, so high they are often difficult to spot from the ground. Up there they are feeding on large insects, especially things like butterflies and dragonflies. When they are seen up close they typically appear all-dark. The males, however, shine with a brilliant purple sheen when the light hits them right. It’s one of the only birds in North America that can really be said to be purple and it’s quite striking.
Purple Martins, or at least the eastern subspecies, are very notable for another reason. They have one of the most strange and notable nesting habits of any North American bird – any bird in general, in fact. They nest almost exclusively in man-made bird houses. And, as a colonial species, it is even more specific, as they nest in specially made large bird houses with many cavities.
Purple Martins eat flying insects, especially things such as bees, wasps, and biting flies. They also eat many insect species which are crop pests. Thus, they are generally desirable birds to have around. Indigenous peoples were putting up martin houses long before Europeans even arrived on this continent. European settlers quickly picked up the tradition from them. And, however long Purple Martins have nested this way, it’s very clear it’s been happening for a long time. Currently, there is only one known eastern Purple Martin colony in natural cavities, in a stand of palm snags near Orlando, Florida. All other eastern Purple Martins nest in houses.
This has made this entire species dependent on human management. It’s not just the houses themselves, either. Other birds can easily push out Purple Martins, meaning for a colony to last more than a few years, people must be actively removing other birds from the house. This is especially an issue with the non-native House Sparrow and European Starling, which readily nest in Purple Martin houses. Due to their reliance on flying insects for food, Purple Martins are also very sensitive to cold snaps. In some especially cold years, they may require the people who keep the colonies to actively feed them by throwing food up into the air.
In winter, Purple Martins migrate to Brazil, mostly to the Amazon Rainforest. Despite the wildness of the landscape there, they still prefer to roost on man-made structures such as buildings and cell towers. On their migratory route they also gather to roost. Now that their nesting season is done, I’ve seen large flocks gathered on power lines at Woodland Dunes.
Purple Martins are a great example of how intertwined ecosystems and the humans that inhabit them are. We have this idea in our mind of some primal wilderness that existed once on this continent, and maybe even still does somewhere. But the reality is that the humans who live here and have lived here have always been affecting the landscape. Enough so that an entire bird species became reliant on us.
The birds I see and hear at Woodland Dunes probably come from the colony set up at Veterans Park. They’re probably all or mostly done nesting for the season by now, but their colonies are very busy and fun to watch when they’re active.
