It’s no secret that the Gulf Coast has a special allure for birders.
But just how many birds migrate every year across the Gulf Coast? With coastlines spanning from Brownsville and South Padre Island along multiple states of coastline to Key West, Florida, anyone wanting to discover the answer to that question would have a lot of territory to cover — and a lot of birds to count.
In fact, it turns out, they’d have billions of birds to count.
A recently published study that includes data from radar and bird watchers has revealed details about spring migrations along the Gulf Coast. The study drew upon the work of citizen scientists and weather radar stations and the conclusions were published this month in the journal Global Change Biology.“We looked at data from thousands of eBird observers and 11 weather radar stations along the Gulf Coast from 1995 to 2015,” says lead author Kyle Horton, an Edward W. Rose Postdoctoral Fellow at the Cornell Lab of Ornithology. “We calculated that an average of 2.1 billion birds crosses the entire length the Gulf Coast each spring as they head north to their breeding grounds. Until now, we could only guess at the overall numbers from surveys done along small portions of the shoreline.”
Researchers wanted to know about more than how many birds were migrating along the coast. They also wanted to examine how these journeys may be affected by climate change. Findings on the timing, location, and intensity of these bird movements were published in the study’s report.Data from citizen scientists came from an app called eBird, which is the Cornell Lab’s worldwide online database for bird observation reports. Sightings from bird watchers helped researchers translate their radar data into estimates of bird numbers. Weather radar detects birds in the atmosphere in a standardized way over time and over a large geographical area.
The radar data reveal when birds migrate and what routes they take. The timing of peak spring migration was consistent over 20 years along the 1,680-mile coastline. But the researchers found that the 18-day period from April 19 to May 7 was the busiest — approximately one billion birds passed over the Gulf Coast in that time span. Not all locations were equally busy, with key hotspots showing significantly higher levels of activity.
And Texas birders could probably guess that the Rio Grande Valley is a reliable hotspot for activity.
“The highest activity, with 26,000 birds per kilometer of airspace each night, was found along the west Texas Gulf Coast,” says Horton. “That region had 5.4 times the number of migrants detected compared with the central and eastern Gulf Coast from Louisiana to Florida.”
The data show Corpus Christi and Brownsville as having the highest level of migration traffic along the western coast of Texas.
Scientists from the Cornell Lab of Ornithology, the University of Oxford, the Smithsonian Migratory Bird Center, the University of Delaware, and the University of Oklahoma conducted this research.
Funding for this project was provided by the Rose Postdoctoral Fellowship, Leon Levy Foundation, National Science Foundation, and Southern Company through their partnership with the National Fish and Wildlife Foundation.