Foraging strategy of Black Skimmers during the non-breeding season

MARIANO Y JELICICH, ROCÍO; FAVERO, MARCO

Congreso; 27th Meeting of the Waterbird Society; 2003

Waterbird Society

Skimmers are known because of their characteristic bill and foraging tactic. Although previous works from North America describe aspects about their foraging behavior, little is known about them during the non-breeding season. In this work we present new information on the foraging ecology of Black skimmers (Rynchops niger) in estuarine non-breeding areas in Argentina. Information on the diet was obtained analyzing regurgitated casts. The structure of fish assemblages was estimated at different areas used by skimmers to forage. Behavioral observations were carried out to estimate the use of foraging patches, foraging effort and success. Silverfishes and Anchovies, comprising both marine and estuarine species, mainly constituted the diet of skimmers. Wind direction had no effect on the relative consumption of marine or estuarine prey; however wind intensity was negatively correlated with the importance of marine ones. Non-significant differences between foraging areas were found in the composition of fish assemblages. However, significant differences were found when only fish found in the diet were considered. Significant differences were found in the use of foraging patches by skimmers, but those were not related neither with the abundance nor the diversity of fish assemblages. Foraging effort increased in areas with higher fish-prey abundance. Tide level had a significant effect on success rates and the number of birds foraging in a patch.