Invading, jumbo snails helping endangered Everglades bird

Preliminary estimates show the Everglades snail kite population increasing by 200 heading into this year's nesting system, according to Audubon of Florida. And that's after last year's drought dried up the endangered bird's key feeding grounds rimming Lake Okeechobee.

The snail kite's resurgence is at least partly thanks to South Florida's influx of a larger, exotic version of the native apple snails that are the finicky bird's primary food source, according to Audubon.

These larger snails reproduce year-round in quantities that dwarf their diminutive native counterparts.

A native apple snail, the size of a golf ball, produces about 30 to 50 eggs at a time during the spring. But the super-sized exotic version that can grow as big as a baseball produces 300 to 500 eggs at a time and keeps churning them out year round.

For environmentalists who usually advocate stopping the spread of species not native to Florida, the benefits of this fast-multiplying snail kite snack create quite the environmental conundrum.

"It's baffling," said Audubon scientist Paul Gray, who specializes in Lake Okeechobee environmental conditions. "Here's my endangered species being saved by an exotic species."

Gray estimates there are about 900 Everglades snail kites living in a territory that stretches from the Kissimmee River to Lake Okeechobee and the Everglades.

Heading into last year's drought, populations of the medium-sized bird of prey plummeted from 3,000 a decade ago to about 700.

More trouble was expected last year when Lake Okeechobee dropped to its lowest level since 2008, drying out the marshes around the lake and killing off much of the native apple snail population.

Amid Lake Okeechobee's decline last year, snail kites began abandoning their nests, leaving some of their young to die.

While the birds struggled on Lake Okeechobee, they had more success nesting along the Kissimmee River and the Kissimmee chain of lakes to the north.

Now the larger apple snails, originally from Argentina and Brazil, are providing a more steady food source.

The exotic snails called "island apple snails" are popular features of the aquarium trade. They end up in the wild when people dump them in canals or other waterways, said Mike Bodle, senior scientists for the South Florida Water Management District.

"They've almost overwhelmed Lake Okeechobee," Bodle, who specializes in invasive species, said about the larger snails. "They lay (eggs) year round. ... It's providing this bigger food base."

Welcoming a modest snail kite recovery doesn't mean scientists are ready to completely shed concerns about the larger snails.

Young snail kites might end up wasting too much energy trying to get the larger snail out of its shell, which could be a long-term detriment, Bodle said.

Also, while the smaller, native apple snails eat algae off aquatic plants; the larger snails eat the plants as well, which could create long-term habitat concerns.

"The jury is still out on what the final effects will be," Gray said.

(c)2012 the Sun Sentinel (Fort Lauderdale, Fla.)
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