Michael McCloy Rio Brazos Audubon Society
Step outside on a clear spring night and listen carefully – you might hear faint, intermittent “tsip”, “zeep”, or “zzt” notes above your head.
Most people are not even aware of the existence of these sounds. These are, in fact, the flight cries of birds migrating above our heads.
Every spring and fall, hundreds of North American bird species make the long and arduous journey between their nesting grounds in the northern United States and Canada and their wintering grounds in Central and South America. .
Many birds migrate at night, including warblers, sparrows, vireos, cuckoos, flycatchers, and even some waterfowl like herons and rails.
Indeed, flying at night has a host of advantages over daytime travel. The stars are thought to aid in navigation, and a generally more stable atmosphere at night reduces additional energy expenditure. It also allows escape from many diurnal predators. There are many theories as to why birds call when migrating at night, including helping flocks stay together and warning of potential dangers ahead.
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These nocturnal flight calls, called “NFC” by ornithologists, are a method to easily study the nocturnal migration of birds by setting up a semi-automated monitoring station.
To the unaided human ear, many of these call notes are indistinguishable. The “zeep” flight call of one species may sound nearly identical to the “tsip” flight call of another. Fortunately, the use of spectrograms and software solves this problem.
Many birds that migrate over or around the Gulf of Mexico eventually cross the coast and eastern Texas on their way north to their breeding grounds in the northern United States and Canada.
As part of a renewed interest in volunteer engagement and science outreach, the Rio Brazos Audubon Society is setting up an NFC monitoring station in College Station this spring and fall.
A remote recording device will be deployed on land owned by Texas A&M University and will be scheduled to record at night. Trained volunteers will then analyze the data using audio processing software and identify any recorded cash calls.
Why is it important to monitor nocturnal migration here at College Station?
Many species that are frequently detected by calling notes at night are reclusive and rarely seen during the day, such as Le Conte’s sparrows. By monitoring nocturnal migration, we can gain a much better understanding of the timing and migratory routes of these species.
This project has the potential to provide additional scientific knowledge on the number and diversity of migratory birds passing over our immediate area on their way to and from their more northerly nesting grounds.
If you would like to learn more about this project and bird migration in the Bryan-College Station area, contact the Rio Brazos Audubon Society at [email protected] or explore their website at riobrazosaudubon.org.
To learn more about the factors that influence bird migration and migratory routes, check out BirdCast, a large-scale project and free resource developed by the Cornell Lab of Ornithology.
Michael McCloy holds a Ph.D. candidate in ecology and evolutionary biology at Texas A&M University, where he studies how songbird communities respond to changes in weather and climate. He has traveled to 49 states and nearly 30 countries with the goal of seeing as many bird species in the world as possible. He leads several projects with the Rio Brazos Audubon Society, including the Night Flight Calls Project and the Audubon Climate Watch Squares program.