Prey capture success and chick diet of Damara terns Sterna balaenarum in Namibia

Abstract

Feeding terns are affected by a variety of environmental conditions. We studied prey capture success of Damara terns Sterna balaenarum in relation to six  variables at two breeding colonies in southern Namibia: tidal phase, wind speed, water clarity, cloud cover, water depth and locality. Damara terns dived most successfully at high tide and least successfully at low tide. Prey capture success improved whereas total dive rate decreased with increasing wind speed. Prey capture success was highest in the least turbid water, but was not significantly affected by cloud cover or water depth, and there was no significant difference  in dive success between localities. The diet of Damara tern chicks were studied throughout Namibia. Of 55 prey items collected, Cape silverside Atherina breviceps, southern mullet Liza richardsonii and Cape anchovy Engraulis encrasicolus were among the most abundant prey species. At least  nine prey species were found in the diet of Damara tern chicks that had not been previously reported from Namibian waters.

Keywords: dive rate, dive success, forage ecology, tide, water clarity, wind speed

African Journal of Marine Science 2011, 33(2): 247–254