The Grand Prairie Bird Alliance says it needs people who are willing to help address a housing shortage — not of houses for people, though. It's a dearth of purple martin dwelling space.
Purple martins are the largest swallow species in north America. They winter in south America, many in the Amazon basin, and fly north to breed each spring.
Bird surveys show the population of purple martins dropped 23% between 1966 and 2019. Retired Illinois Wesleyan University Biologist Given Harper said the bird alliance is trying to enlist and train volunteers to be purple martin stewards who check bird houses and remove nests of starlings and house sparrows that can out compete purple mountains.
Harper said purple martins are very cool birds.
“They have this beautiful chirping sound. They nest colonially. Multiple martins will nest in a single box and when they are all together and chirping, to me, it sounds like magic,” said Harper.
Purple martins need humans. They nest in tree cavities, either holes that have rotted away or those bored by woodpeckers and other birds. As humans have removed a lot of forested area, their natural nesting places have become scarce.
“Historically they nested in hollowed out gourds put up by indigenous peoples. And today in eastern north America the entire eastern population is almost completely dependent on boxes, structures put up by humans,” said Harper.
He said native Americans probably valued the martins because they feed on flying insects including mosquitos. And hoovering up bugs around indigenous settlements was a good thing.
“When they are feeding young, they catch thousands of insects each day,” said Harper.
The bird alliance has placed seven boxes, or houses, for martins around the community. Three are at Tipton Park with a total of 68 compartments. A box at White Oak Park has 16 units. And there are three sets of plastic gourds at Lake Bloomington. He said the community could support more than a dozen additional boxes.
“Because they are aerial insectivores, they like open areas. In particular we try to place boxes somewhat close to bodies of water because especially in the latter part of the breeding season they catch a lot of aquatic insects,” said Harper.
Martins arrive in Central Illinois in late March or early April. Breeding starts in May. Typically, by the end of July and early August they have begun flying south.
“One of the concerns of climate change is you tend to get extreme weather. So, sometimes in early spring it will be warm later in spring you’ll have cold snaps. That can kill martins. There are no flying insects when it’s really cold and in extended cold periods they would have difficulty surviving,” said Harper.
He said the number of insects around the world is declining, which could also affect purple martins. And gold mining in south America may be a threat. Some studies have detected significant mercury levels in martin feathers. Miners use mercury to separate fold from raw ore and it can enter water sources and travel up the food chain through insects to birds.
He said the bird alliance would like to find volunteers to be stewards of martin houses. That involves a little training, and checking nesting boxes every week in the spring and summer to make sure starlings and house sparrows don’t move in. He said those non-native birds can outcompete or even kill purple martins or remove their eggs from the boxes.
Avian ecology expert Given Harper will give a workshop on purple martins Sunday, Jan. 26, from 1-3 p.m. at Medici restaurant in Normal. It's open to anyone with a $10 ticket and reservation available at the website of the Grand Prairie Bird Alliance.
