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Texas Communities Relieved as Season Change Triggers Migration for Nuisance Birds

One of the most frequent indicators that a change in seasons is approaching is the migratory patterns of birds.

The destinations to which certain birds will travel and the specific timing of their southward departures may differ, but the migration period has begun.

In several Texas communities, one species, the Cattle egret, has worn out its welcome.

In Houston, the birds annually take over a local park for their spring and summer home, causing one section of it to be closed to the public, ABC 13 in Houston reported. Local residents have complained about an odor in the park as well as health hazards from bird droppings near a community pool.

Cattle egrets can be found in many parts of the country, but they are predominantly found in agricultural, wet habitats in the southeastern and eastern U.S. As the name implies, the birds can tend to be found around grazing cattle.

The trouble with the birds often comes in their rookeries, or breeding colonies, where dozens to thousands of birds can gather. Often times the rookeries are near residential or public areas, with disruptions coming in the form of noises or a pungent odor from abundant bird waste.

"It's not uncommon for them to be in areas that are close to people," said Jeff Kelly, associate professor of biology of the University of Oklahoma Animal Migration Research Group. Kelly cited airports and golf courses as several places where they can congregate and cause issues.

Kelly said that this is the time of year is when the egrets will begin to fly south to Mexico and Central America. He added that sudden changes in weather, such as wind patterns and temperature, can induce birds to migrate.

"This time of year, you might have birds in migratory condition that are ready to go," he said. "But when they decide to leave is often timed with synoptic weather conditions that will give them favorable winds and help them avoid unfavorable temperatures."

The situation in Houston wasn't the only reported instance of the pesky birds raising concerns.

This past April, the city of Wichita Falls, Texas, and Sheppard Air Force Base informed residents to call and report any sightings of the birds. The town is well acquainted with the species because in July 2013, a Cattle egret caused a non-fatal crash of a T-38c Talon training aircraft.

Removing the birds is a tricky matter, as the species, along with all migratory birds, is protected under the Federal Migratory Bird Treaty Act. The act ensures that rookery sites are protected once they are established.

"Usually non-lethal scaring techniques are used to move birds," said Paul Curtis, an associate professor and extension wildlife specialist with a focus on reducing human-wildlife conflicts at Cornell University.

Curtis said it depends on the situation and how urban the environment might be to determine such techniques. For instance, if it's a park area with not many houses nearby, lasers or firecrackers can be used and that will disturb birds from roosting.

In the Houston area, Curtis said there could be egrets that stay year-round, but often numbers pick up this time of year as migrants move through.

These problems aren't just restricted to Cattle egrets, Curtis said. Similar problems can be found with European Starlings, who also migrate south this time of year and can gather in urban areas.

There are two possibilities for the reason these problems arise, according to Kelly. The first is that humans unknowingly develop in areas that were traditionally long-time rookery sites, and birds become displaced.

The second is that humans build habitats that are great rookery sites, such as parks with big ponds or lakes with islands that have lots of shrubbery.

"This can be fine if the developers understand that they are creating great rookery sites, but often that is not the plan and when thousands of egret and other waterbirds show up, they [are] treated as a nuisance," Kelly said.