Purple Martins swarm
The number of Purple Martins leaving the roost at the same time is large enough to be detected on weather radar.

Erie, PA (August 17, 2021)—Purple Martin pre-migratory roosts are forming now.

North America’s largest species of swallow, Purple Martins nest and raise their families in North America and winter in the rainforests of Brazil. East of the Rocky Mountains, Purple Martins nest almost exclusively in human-supplied housing. They are one of America’s most well-loved songbirds, known for their chattering song, aerial acrobatics, insect-eating habits and their tolerance of humans.

In late Summer, after leaving their nesting colonies, Purple Martins gather in huge flocks to feed, socialize, and rest before migrating. This activity, known as pre-migratory roosting, can attract hundreds of thousands of birds to sleep in one small area, arriving at sunset en masse in what Joe Siegrist, President of the Purple Martin Conservation Association (PMCA) calls “an amazing natural spectacle”. “As the sun begins to set, all of a sudden tens…even hundreds of thousands of Purple Martins appear out of nowhere in locations across the country. Their swirling acrobatics and sheer numbers are a phenomenon that everyone needs to witness”, Siegrist adds.

Purple Martins are roosting
Purple Martins are roosting

Purple Martins leave their roost near dawn in a mass exodus. The number of birds leaving the roost at the same time is large enough to be detected on weather radar. It looks like an expanding ring on the radar map. By studying radar data the PMCA is able to locate possible roosts located around North America.

Roost are typically associated with larger bodies of water where reed beds and dry islands with low, thick vegetation provide sanctuary from predators and a micro-climate warmer and less windy than land. They are also found in urban and suburban settings, sometimes formed in trees or on man-made structures such as bridges and pipes. 

Depending on location, roosting can begin in mid-June and run through mid-September, peaking at the end of July to early August. Martins can come from hundreds of miles away to roost. Individual birds may use a roost for several weeks before migrating but the roost itself may last for 8-12 weeks or more.

To follow along with the Purple Martins’ roosts and learn more about how you can help conserve this treasured bird, visit www.purplemartin.org. Roosts are currently occurring all over the United States. To find a roost near you visit the PMCA’s map of roost locations at: roost.purplemartin.org. In addition, people interested in learning more about how to attract and care for Purple Martins can receive a free booklet by contacting the Purple Martin Conservation Association by emailing [email protected] or calling 814-833-7656.

Based in Erie, Pa. the Purple Martin Conservation Association is an international tax exempt, nonprofit organization dedicated to the conservation of the Purple Martin through scientific research, state of the art wildlife management techniques and public education.

The PMCA serves as a centralized data-gathering and information source on the species, serving both the scientist and Purple Martin enthusiast.  The PMCA’s mission is educating martin enthusiasts in the proper techniques for managing this human-dependent species. 

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