Habitat Selection and Breeding Success of Black Terns (Chlidonias niger)
in Impounded Wetlands in New Brunswick

Laurel Bernard
M.Sc., 1999

 

ABSTRACT

There are a third as many Black Terns nesting in North America today as there were 30 years ago, most likely due to the loss of wetlands suitable for nesting. The Black Terns along the Saint John River floodplain in New Brunswick prefer to nest in impounded wetlands; however only a few of the impoundments are used even though they all appear to provide suitable nesting habitat.

My objectives were to determine the environmental cues Black Terns (Chlidonias niger) use for habitat selection by relating physical and biological characteristics of impounded wetlands with use by this species. I also determined the quality of the habitat by relating reproductive success to impoundment characteristics. I examined habitat use and quality at two scales: the impoundment level and the nest site level. I also examined habitat selection using social attraction, tested by using decoys and calls, and I measured the degree of site fidelity.

Size of impoundment, vegetation density considered concurrently with water depth, and abundance of odonate prey determined use at the impoundment level. Features important at the nest site level included density of vegetation, amount of open water, and amount of cover. Black Terns have weak social attraction and low site tenacity. One impoundment had higher breeding success, and hence higher quality habitat, than the others but there were no discernable differences in habitat variables at the impoundment level. Successful nests were initiated earlier, were on higher nesting substrate, and had more cover to protect against predators and the elements.

Laurel Bernard is currently working for the Nature Conservancy of Canada.

FUNDING ACKNOWLEDGMENTS

NSERC

Eastern Habitat Joint Venture

NB Fish and Wildlife