Gulf Coast Birders: Get Ready for 2 Billion Birds

By Carley Eschliman and Pat Leonard

March 31, 2019

Graphic by Jillian Ditner. Data from Cornell Lab of Ornithology postdoctoral researcher Kyle Horton. Birds by Tom Auer/ML — Eleven weather radar stations from Brownsville, TX, to Key West, FL, also track where birds migrating from Central and South America make landfall on their northward spring journey across the Gulf of Mexico. *Graphic by Jillian Ditner. Data from Cornell Lab of Ornithology postdoctoral researcher Kyle Horton. Warblers by Tom Auer/Macaulay Library.* See larger image.

From the Spring 2019 issue of Living Bird magazine. Subscribe now.

College kids aren’t the only ones who flock to the Gulf Coast for spring break. Birders know the Gulf is the best place to catch the spring migration wave of Neotropical migratory songbirds when it crashes on shore. Now scientists know how many birds make up that wave.

Using data from 11 weather radar stations along the Gulf Coast from Texas to Florida, the researchers calculated that on average 2.1 billion birds make landfall from March to May during spring migration in the Gulf. The findings—produced by a research team that included scientists from the Cornell Lab of Ornithology; the Universities of Delaware and Oklahoma; Oxford University; and the Smithsonian Migratory Bird Center—were published in the journal Global Change Biology in January.

Most Dangerous Cities for Migrating Birds

New radar ornithology research from Cornell Lab scientist Kyle Horton identified the cities that pose the greatest dangers to migratory birds, due to light pollution that raises the risk of collisions with buildings. The research, published in the journal Frontiers in Ecology and the Environment, ranked these major U.S. metropolitan areas as the most hazardous spring bird migration routes, due to their light pollution and location within major flyways:

Chicago
Houston
Dallas
Los Angeles
St. Louis

Kyle Horton, an Edward W. Rose Postdoctoral Fellow at the Cornell Lab, was lead author on the research. Using advanced algorithms and supercomputing power, Horton and his team analyzed archived radar data containing almost 1 million weather radar scan images from springtime between 1995 to 2015, then cross-referenced the radar data with eBird observations. They found that a 19-day period from April 19 to May 7 was the busiest window for spring passage among a group of Neotropical migratory songbird species including American Redstarts, Canada and Cape May Warblers, and Baltimore and Bullock’s Orioles. Altogether, approximately 1 billion birds pass over the Gulf Coast in just those three weeks.

Horton says the Texas Coast had five times more migrant birds detected than any other area in the Gulf Coast. Radar stations in Corpus Christi and Brownsville had extremely high levels of bird migration, while on the other side of the Gulf, Jacksonville, Florida, also stood out as a spring migration hotspot. Horton thinks northeast Florida could be a major landing point for birds migrating north from the Caribbean and South America.

Horton says knowing where and when peak migration occurs can inform city and regional efforts to turn off lights and power down wind turbines, which are known collision threats to migratory birds.