Houston Audubon is once again inviting the public to witness the phenomenon during its annual Purple Martin Watch Parties, with the first taking place Saturday. Weather permitting, the watch party begins with a 7:45 p.m. meeting in the Another Broken Egg Cafe parking lot near Interstate 10 and Westgreen Boulevard (20950 Katy Fwy.).
The Katy roost is a new viewing location for Houston Audubon’s watch parties. In recent years, Houston-area roosts have formed in Stafford near the Old Navy Fountains shopping center and around Willowbrook Mall.
The next two watch parties are scheduled for Aug. 1 and Aug. 15. Their locations will be announced the week of each event after volunteers scout known roost sites and track the birds on weather radar. Because purple martins sometimes shift roosts unexpectedly, locations can change at the last minute. Houston Audubon posts updates on its website.
Houston Audubon has hosted the watch parties since 2011. Attendance typically ranges from 100 to 250 people, with last year’s events averaging about 225 attendees.
Houston is a major pre-migratory staging area for purple martins, with some local roosts attracting up to 500,000 birds before the species begins its annual migration to South America, according to Houston Audubon.
Purple martins are the largest swallows in North America. Despite their name, they aren’t actually purple. The dark feathers of adult males reflect sunlight in a way that creates flashes of metallic blue and deep purple.
After raising their young each spring, the highly social birds gather into massive flocks, feeding on insects before making the long journey across the Gulf of Mexico to their wintering grounds in South America.
As dusk approaches, the birds begin circling overhead, creating a massive swirling cloud before dropping into their roosting trees for the night. The aerial display lasts about 45 minutes.
When the birds depart at sunrise, hundreds of thousands take flight at nearly the same time, creating what meteorologists call a “roost ring,” or donut-shaped signature, on Doppler radar.
According to Houston Audubon, the watch parties give visitors a chance to learn about the birds’ migration, how the flocks are tracked on weather radar and ways to help protect the species.