Snail Count for Snail Kites

The Florida apple snail population declined after two severe droughts in the early 2000s. How did Snail Kites, who rely on the species as their sole food source, survive?

The iconic Everglade Snail Kite, which relies on wetland ecosystems like the Everglades, experienced a major population crash in the early 2000s. After two significant droughts, their numbers plunged from more than 3,000 birds to approximately 700 in just 10 years. The problem? As parts of the Everglades — including Lake Okeechobee and South Florida — went dry, the kites’ only food source, the Florida apple snail, dried out too.

At the same time, exotic apple snails from South America, presumably from the aquarium trade, got loose and established themselves in Florida lakes and wetlands. These snails grow much larger than our native snails, are more resilient to dry conditions, and can spread rapidly. Luckily, the kites learned to feed on these invaders, contributing to an unlikely success story where kites have rebounded to approximately 3,000 birds today. Limpkins, another snail specialist, have rebounded as well.

Kite recovery is good news but appears almost completely based on the occurrence of exotic snails. Native snails have not come back, as many expected. Therefore, in conjunction with the Snail Kite Coordinating Committee, Audubon’s Everglades Science Coordinator, Paul Gray, PhD, developed a community science project to count snail egg clusters at wetlands across South Florida to determine where snails are and — as importantly — where they are not. Brett Fitzgerald of the Angler Action Foundation donated an app that allows scientists and volunteers to quickly report snail egg clusters.

COVID-19 restrictions limited counting opportunities, but to date, more than 450 observations have been reported. So far, volunteers have recorded native snail eggs at about 35% of the survey sites and exotics at 40%. Oddly, both species of snails were seen together only 20% of the time. At the other 80% of the locations, community scientists identified one snail or the other, suggesting that the two species select somewhat different habitats, or that competition between the two species limits habitat use.

At the fall meeting of the Committee, the future of snail egg surveys will be discussed. We are hopeful that this new community science project will scale up with time and will provide an important data set that will inform kite recovery plans and invasive species eradication efforts.

This article was published in the Fall 2022 State of the Everglades report.

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