Visitors are invited to flock to Cahokia Mounds State Historic Site near Collinsville on Saturday to learn how they can help purple martins.
Volunteer John Miller will present a program on purple martins from 10 to 11 a.m. Saturday. Local members of the St. Louis Audubon Society and the Purple Martin Conservation Association will talk about the natural history of the migratory birds, including their total dependency on human-provided housing, and will provide tips for hosting them.
Meet at the large rack of nesting gourds on the parking lot south of the visitor’s center. The rack of gourds will be lowered briefly to demonstrate a next check of the baby purple martins. Information about purple martins will be handed out. The event is free and open to the public.
The colony of purple martins has been living at the site since 2008.
Purple Martin facts
Size: With a length of 7-8 inches, the purple martin is the largest swallow in North America and one of the largest in the world.
Color: these birds are not actually purple. Their plumage is a dark blue-black with an iridescent sheen. Depending on the light, they can look blue, purple or even green
Diet: Purple martins eat primarily flying insects, and they catch the majority of their prey in midair. They even drink in midair, flying over a pond, lake or stream and scooping water into their bills.
Myth: Mosquitoes make up only a small portion of their diet, despite rumors that the birds can eat up to 2,000 mosquitoes per day.
History: Centuries ago, Native Americans hung gourds for the birds to nest in, hoping to attract them to help keep insects away from crops.
Nesting: Purple martins will return to the same nesting site year after year if it is still suitable. Adding new houses to colony sites can help birders accommodate growing purple martin families.
Speed: The top flight speed of purple martins is greater than 40 mph.
Migration: Purple martins travel from North America in the summer to South America, as far as Brazil and Argentina, in the winter. The full migration can take two to three months to complete.