Roof-Nesting Least Terns Travel to Forage in Brackish/Marine Waters

Abstract

Sternula antillarum (Least Tern) are small, migratory seabirds that are listed as threatened or endangered in every state in which they occur. While their natural nesting habitat is open beach, Least Terns have adapted to nest on flat tar and gravel roofs, sometimes many kilometers inland. We used the “fish drop” technique to collect fish that birds dropped around a roof colony in Pinellas County, FL to assess use of fresh and saltwater fish species as prey. We collected 37 fish from 12 different species. The most common (n = 11) was Dorosoma petenense (Threadfin Shad), a species found primarily in marine/brackish waters, but often stocked in man-made freshwater ponds to supplement piscivorous fish prey. Eighteen of the remaining 26 fish, encompassing 7 of the remaining 11 species, are marine/brackish species, 5 individuals are freshwater species, and 3 are freshwater/brackish species. Roof-nesting Least Terns appeared to forage in stormwater ponds and a lake found near the colony, but they also traveled a minimum of 4.8 km to forage in marine/brackish waters. Roof nesters may face greater challenges than beach nesters, because they are potentially exposed to more pollutants in stormwater ponds and expend more energy and time to travel farther to forage at saltwater sites.