Great-tailed grackles gather for their massive winter roost sites in mid-August and start to disperse in late March, but anyone who has lived long in Austin knows that warm summer nights can be as full of grackles as a night in December.

The huge roosts of grackles you’ll find across the city are great-tailed grackles gathering by the thousands, usually mostly male. They gather in the parking lots of grocery stores and restaurants because they can find excess food easily and because modern developers often add trees to parking lots. Between the trees and the power lines, these parking lots become the perfect places for grackles to congregate.

Residents of Austin have a complex relationship with great-tail grackles, which are known to flock grocery stores, restaurants and parking lots in large numbers.

In 2011, Elanor Dean, a graduate student at the University of Texas, studied 15 roosting sites around Central Texas to try to answer questions about access to food and even how lighting might affect the large grackle roosts. Some grackles change roost sites from night to night, but Dean concluded that the height and width of trees, particularly live oaks, affected the likelihood of grackles more than the prevalence of food or other variables.

When conditions are favorable, grackle roosting hotspots in Austin include nearly every H-E-B and the intersection of Interstate 35 and William Cannon Drive. Other popular roosting sites include Sam’s Club at La Frontera in Round Rock and Costco in Circle C.

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