Eavesdropping on Night Skies

By Sue Schwaller

Millions of spring migrants are hitting the road this spring and all they need to pack is their courage and some tunes. Texas is a major route for migrating birds. Throughout the state and along the Gulf coast, birds are flocking through Texas skies.

Large numbers of these spring migrants travel at night. Nocturnal migration sounds exotic, but our winged travelers aren’t on a pleasure trip. They’re flying as swiftly as possible to reach their northern breeding and nesting habitat. Flying in the dark typically affords them gentler winds and a better chance of not becoming a predator’s meal.

Many of the nocturnal migrants produce flight calls or chip notes along the way. Step outside during a quiet spring night and listen for a twittering above you; it’s their road songs you’ll be hearing. Researchers don’t know exactly what birds’ chip notes are communicating. They’re not like a bird’s typical song and not all species vocalize during flight. But since they are flying through darkened skies, most likely their calls are saying, “follow me” or “watch out, danger ahead” or just plain encouragement, “you can do it”.

In an effort to protect bird populations and explain nighttime migration and flight calls researchers are monitoring nocturnal flight calls. As birds lift off into evening skies, listening devices are eavesdropping. From microphones and digital audio recorders aimed into the night skies, to birders’ trained ears, migrants are being tracked. You can observe how monitoring is accomplished by visiting Old Bird. This nonprofit organization was formed to facilitate acoustic monitoring of flight calls during nocturnal migration. On their website you’ll find resources for setting up your own listening station and step by step detail on gathering and distributing night flight calls.

Bird conservation is at the heart of avian acoustical monitoring. Many bird species are declining and although daylight bird counts and bird banding are being utilized, the more sensitive acoustical monitoring of nocturnal flight calls will be extremely important in conserving populations. Migration at it’s best is difficult. During migration birds are forced to fight not only nature’s forces of fog, rain and northerly winds, but also man made obstacles such as loss of stop over habitat, power lines, communication towers, wind turbines and tall buildings.

For scientists trying to protect bird populations two ill sited wind energy projects planned for Kenedy County, Texas are of grave concern. These wind industrial sites are directly in the most active migratory bird pathway in North American. Not only will these sites destroy wetland habitat, but also the blades of the wind turbines will be a Mixmaster for birds forced down during grounding conditions as well as a hazard for locally occurring species. Researchers have stated that this development could be the cause of the greatest avian mortality in North America.

The next time you find yourself outside on a spring night stop and listen. You might hear a dickcissel, warbler, tanager or bunting. It wasn’t easy for them to arrive safely high above your head. Use your voice to speak up for them. Visit the Coastal Habitat Alliance link, How Can I Help, and let your voice be heard.