William & Mary

New aerial census logs thousands of waterbirds

Bryan Watts and Bart Paxton of the College of William & Mary’s Center for Conservation Biology have successfully completed an aerial survey of the Pacific Coast of Panama to estimate and map waterbird populations during the peak of fall migration. Flying at an altitude of only 20-30 meters in a Cessna with pilot Carlos Diaz, the survey team flew 1,565 kilometers of shoreline in three days between in late October, 2008.

More than 490,000 shorebirds, seabirds, herons and egrets were counted and mapped. Survey flights were supported by the United States Department of Defense Legacy Program and the Center for Conservation Biology (CCB) with assistance from the Panama Audubon Society and the Smithsonian Tropical Research Institute. The survey identified several key estuaries that supported high densities of waterbirds including the Golfo de San Miguel, Bahia de Panama, Bahia de Parita, Golfo de Montijo and Bahia de Muerta. Watts said that collectively, these productive estuaries were found to support 98 percent of the waterbirds detected. All bird groups reached their highest densities along the shoreline of the Bahia de Panama.

Results of the survey showed that a 30-kilometer segment just east of Panama City accounted for less than 2 percent of the Pacific Coast shoreline surveyed, but supported 72.5 percent of all birds detected. Waterbird densities within this small area averaged 12 birds per meter of shoreline, making it one of the most significant waterbird conservation areas throughout the Americas.

“For many groups of migrant birds, Panama is the most significant continental crossroad in the western hemisphere,” Watts said. “Hundreds of millions of birds pass through this small country each year on their passage between breeding and wintering grounds. The annual cycle of many waterbird species appears to be structured around the resources provided by the Pacific Coast of Panama.”

He explained that the Bahia de Panama, in particular, appears to play a prominent role in the structure of waterbird migration systems throughout the Americas. Watts stressed that protection of habitats and resources within this site is critical to the conservation of waterbirds on a hemispheric scale.