During beach bird nesting season, it’s all hands on-deck. This is especially true for Audubon staff and volunteers in the Greater Tampa Bay area, who go above and beyond to ensure birds like Least Terns find the habitat they need to raise their young each spring and summer. 

Because beach habitat across the region is busy with human visitors, many beach-nesting birds are instead finding refuge on rooftops. While rooftop nesting colonies can be as productive as beach colonies and provide relief from most forms of disturbance, these chicks face a threat unique to rooftops: falling off. 

Audubon Florida has monitored rooftop nesting in Florida for decades. In the past, volunteers who found chicks fallen from their rooftop colony had two choices: Take the seemingly healthy chick to a rehabilitator where it would stay until fledging without the benefit of learning how to be a tern from its parents; or return the chick to the rooftop. Anecdotal evidence has long suggested these returned chicks fared well, but a new study reveals more about how many survive to adulthood and go on to raise their own families.

From 2011 to 2022, under permits issued by the U.S. Geological Survey and Florida Fish and Wildlife Conservation Commission, past Audubon Florida Director of Bird Conservation Marianne Korosy, PhD, and renowned bird biologist Beth Forys, PhD, (Eckerd College) conducted a study in which biologists placed colored bands on the legs of any Least Tern chicks they returned to a rooftop following a fall. With a squadron of volunteer rooftop monitors, co-author and Audubon Coastal Biologist Jeff Liechty set out to resight the birds they banded in later breeding seasons on beaches, piers, and rooftops throughout Florida. 

Over the course of nine years, biologists banded a total of 168 healthy Least Tern juveniles that had fallen from 16 different nesting rooftops. Fifty of those birds were resighted a total of 347 times, with an overwhelming majority coming from a single, narrow staging beach (not a Least Tern nesting area) along the Gandy Bridge causeway in the middle of Tampa Bay. Seven of the terns were resighted while nesting: three on nearby beaches, three at rooftop colonies in Pinellas County, and one on a Levy County beach. Resighting birds while they are nesting means they have survived to adulthood and are ready to raise the next generation of Least Terns.

A 30% resighting rate is good: It means the birds are successfully fledging after placement back on rooftops. The banding study also confirmed that at least 39% of those birds survived to one year of age. After one year of age, 82% of the terns survived each year thereafter. 

The team published their peer-reviewed paper in Avian Ecology & Conservation earlier this year—the first published estimate of juvenile Least Tern survival rates and scientific evidence that returning fallen chicks to the roof results in their long-terms survival. The data are valuable for understanding population dynamics and show that putting juveniles back on rooftops is a viable management tool for Least Terns and potentially other rooftop-nesting seabirds. 

Although rooftops may offer an alternative nesting habitat for Least Terns, juvenile survival likely depends on habitat quality after they leave the rooftop.

This work would not be possible without dedicated volunteers with St. Pete Audubon Society and Clearwater Audubon Society, who monitored and chick-checked rooftops, rescued chicks, and re-sighted banded birds across the region. Read the published study here: ace-eco.org/vol19/iss1/art7/

This article appeared in the 2023 Coastal Report.