Least Terns are colonial nesters, raising their chicks in large flock groups, and naturally nest on open sandy beaches throughout the coastal United States. Eggs are laid in a shallow scrape in areas with little to no vegetation and no overhanging trees. Nesting together in a large flock provides chicks greater protection from predators since there are more adult eyes on the lookout.
However, due to development, sea level rise and human disturbance, much of the natural beach nesting areas has declined, leading to a decline in Least Terns throughout their range. Least Terns are now on the Federal Endangered Species list in California and along the Mississippi River and are listed as Threatened by the State of Florida.
In the face of beach disturbance from development, vehicles, people and pets, Least Terns have started using an alternative nest site on top of tar and gravel rooftops. The Florida Fish and Wildlife Conservation Commission recently reported that nearly 80% of Florida’s Least Terns are nesting on rooftops! While these rooftops may provide protection from disturbance and predators, there are drawbacks that do not make rooftops an ideal nesting situation.
Least Terns can nest in flocks as large as several hundred birds with on average two eggs per nest. This can result in a great many chicks and adult birds occupying a relatively small area. Adults are very busy flying back and forth from foraging grounds to the nest site and can become noisy and messy around the nest building. Within a few days after hatching, chicks start to walk around and can fall off roofs that do not have a lip of barrier, or become washed down a rainspout after a storm. Once a chick is on the ground it faces numerous hazards such as feral cats and dogs, fire ants, vehicles and foot traffic, and over-heating. Neither the chick nor the adult can get the chick back on top of the roof themselves.
Luckily, Audubon has many concerned volunteer bird stewards who are trained on how to carefully assist the chick back to the rooftop. There is also a newly developed protocol for temporary fencing on those roofs that lack a lip or barrier to help prevent falling chicks. Audubon and the Florida Fish and Wildlife Conservation Commission collaborate with building owners and managers that have nesting Least Terns to try to harmoniously accommodate the terns and store patrons. Even though rooftops may not be the natural or ideal nesting site, they do provide an alternative that could be managed to ensure successfully fledged chicks and the continued survival of Least Terns.
If you are interested in helping Audubon with beach-nesting and rooftop bird surveys and monitoring in the northeast region, please contact Audubon's Stefanie Nagid at firstname.lastname@example.org.