Mortality mystery: Why all the dead egrets on I-75?

Egrets are the latest casualties in a shocking series of mass wildlife die-offs that have claimed manatees, shorebirds, fish, sea turtles and dolphins

Splayed along Interstate 75, mostly between Corkscrew Road and Golden Gate Parkway, the carcasses were mostly cattle egrets but included at least one snowy egret.

In one 3-mile stretch, more than two dozen birds sprawled on the shoulder, most in awkward postures suggesting they'd been hit.

Sitting in his all-terrain vehicle on the highway's shoulder, Don Blackwood said he's never seen anything like this in the six years he's been working for DBI, the company that maintains I-75. "I'm not a veterinarian so I can't say what's happening, but there are dead ones all over out here," he said.

Gesturing at a tractor in the distance, Blackwood pointed out an egret flock fluttering behind the machine. "But they're not all dead," he said. "They follow behind when we mow, picking up the bugs." 

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The Florida Fish and Wildlife Conservation Commission is aware of the die-off, said spokeswoman Melody Kilborn, but hasn't identified a reason. "We're definitely looking into the circumstances of this," she said.

James Beever, of the Southwest Florida Regional Planning Council, said cattle egrets are known to fly into moving vehicles, though the scientific literature includes other causes as well. "There have been cattle egret mass mortalities from migration exhaustion in the Dry Tortugas, communicable diseases like salmonella, collision with vehicles and poisoning from pesticides for both invertebrates and vertebrates. If the egrets had been foraging on dead sea life they may have picked up red tide toxin."

Brian Bohlman, of Sanibel's Clinic for the Rehabilitation of Wildlife, can't recall anyone recently bringing in injured birds from that region but said the deaths might be from a controlled burn in south Lee County. "The smoke has the potential to cause more birds to move across the highway and lead to more interactions with vehicles," Bohlman said.

The fact that the birds were on both sides of the road may also point to some kind of poisoning, Beever said. "Birds suffering from sublethal toxicity can behave as though they are drunk and fly into or walk into the path of vehicles."

To report bird die-offs, contact the FWC online: http://legacy.myfwc.com/bird/default.asp.

Five things to know about cattle egrets

It's the smallest egret in Florida. The Sunshine State also hosts great egrets, snowy egrets and reddish egrets, but at less than a pound, the cattle egret is the littlest.

It's not native. "The cattle egret is truly an invasive exotic," said retired FGCU professor Jerry Jackson, the region’s pre-eminent ornithologist. "They normally are ... associated with large grazing mammals in Africa."

It's got big-screen experience. Cattle egrets have a cameo in "Wind Across the Everglades," Jackson said, which may be their first-known Hollywood appearance. See for yourself at a Dec. 10 screening of the movie, which will benefit Calusa Waterkeeper.

They're not afraid of giants. In Africa, where they originate, they pick insects off large critters like water buffalo, rhino and elephants. 

They're not picky. In addition to bugs, cattle egrets eat fries and burgers and are often seen hanging out in fast-food parking lots. Just ask Henry the egret.

— Source: Dr. Jerry Jackson, The News-Press archives