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In total, they looked at over 100 tiger sharks, and a shocking 40 percent of those bellies contained some form of avian remains. “All of the sudden, it’s not just a gee-whiz observation,” Drymon says, “it’s something they do relatively frequently.”
Once again enlisting the help of Feldheim, the team found evidence of 11 different bird species in shark stomachs, including swamp sparrows, yellow-bellied sapsuckers, house wrens, and white-winged doves. Curiously, though, Feldheim wasn’t able to find any marine bird DNA. So Drymon turned to another colleague, bird ecologist Auriel Fournier who’s currently affiliated with the Illinois Natural History Survey, to figure out why tiger sharks were eating so many terrestrial birds.
Bat - Birds - Species - Airspace - Gulf
Right off the bat, they realized the birds were all migratory species, which would put them in the airspace over the Gulf twice a year. In the spring, many birds fly north from the Carribean, Central America, and South America to spend warm summers nesting in North America. Come fall, they make the return trip, often with new offspring in tow. To cross-reference the timing of when birds should be flying over the Gulf with when bird remains ended up in shark stomachs, the team used the citizen science database eBird, where users log birds they encounter from day to day. Lo and behold, tiger sharks ate the most birds in early September, right at the...
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