Nest taphonomy of Poplar Island common terns and Caribbean flamingos of the Smithsonian National Zoo

Abstract

Theropod nesting localities suggest some dinosaurs incubated eggs in a manner similar to modern birds; however, taphonomic studies of modern nesting localities are limited. Here, I document Common Terns (Sterna hirundo) and Caribbean Flamingos (Phoenicopterus ruber) nesting sites at Poplar Island, Chesapeake Bay, MD, and Smithsonian National Zoological Park, Washington D.C., respectively. Sterna hirundo construct scrape nests with loose vegetation and produce 2-3 eggs; P. ruber build mud mounds containing one egg. Both species exhibit biparental care. Nests were surveyed on multiple occasions. Documentation included nest composition, density, and distribution, as well as eggshell concentration and orientation. Of 80 tern nests with 193 eggs, 12 nests hatched, 7 were predated, 31failed, and 30 were of unknown fates. Thirty-two flamingo nests averaged 32 x 31 cm, with mean nearest neighbor distance of 63.8 cm. Both species displayed abundant eggshell at nest centers. Concave-up eggshell characterized hatched and predated nests, whereas trampled areas favored concave-down. Wind or colony members likely transported random eggshell present on the colony. Eggs buried in nest and soil indicated adult abandonment. The results of this study may help determine nest fate for modern birds and provide paleontologists with physical characteristics to consider when excavating fossil sites.