We're all familiar with the annual migration of spring breakers.

But a lesser known spring migration happens every year in mid-April as migrating birds return from their winter homes in Central and South America to breeding grounds in the United States and Canada. A recent study estimated 2.1 billion birds migrate across the Gulf Coast region each spring, spanning the area from Texas to Florida.

One stop on this migration "flyway" is Fort Morgan State Park, Alabama, located at the tip of Mobile Bay. Birds leaving from the Yucatan peninsula in Mexico make an overnight flight hundreds of miles long over the Gulf of Mexico to land hungry and tired on the shores of Alabama.

Meeting them every spring is a group of volunteer researchers and wildlife experts, who set up series of fine mesh nets among the trees to capture, identify and catalog these birds. Each bird is then fitted with a tiny metal band around its leg that bears a unique identification number.

If the bird is caught again, researchers can tell where that particular bird has been. Researches use the information they gather every year to gain insights on how bird migration is impacted by changes in climate and habitat loss.

The week-long bird-banding event is organized by the Birmingham Audubon Society, the Alabama Department of Conservation & Natural Resources and Mississippi State University, with help from partners Gulf Shores & Orange Beach Tourism, the Edwin L. and Elizabeth L. Skelton Foundation, the Alabama Historical Commission and the Mobile Bay Audubon Society.

The annual event is open to the public and offers an excellent opportunity to see some of these migratory birds up close and watch the collection and banding process. Here are some of the photographs I took from this year's event, which was held April 16-20.