MEPS 506:291-302 (2014)  -  DOI: https://doi.org/10.3354/meps10834

ABSTRACT: Analyses of the behavior, distribution, and abundance of seabirds tend to identify the importance of habitat variability and prey availability, yet ignore social facilitation. To quantify such influences on the foraging strategies of common terns Sterna hirundo and roseate terns S. dougallii, I implemented nonlinear density-surface models with distance sampling, using remotely-sensed habitat covariates. I collected tern and prey data aboard trawl surveys off the coast of Massachusetts, USA, selecting the 3 dominant regional prey categories: northern sandlance Ammodytes dubius, herring (Clupea spp., primarily Atlantic herring C. harengus), and anchovies (Anchoa spp.). The best models showed significant positive effects of tern flock size and variable sandlance abundance on common and roseate tern spatial patterns; additional predictors included herring abundance, relatively shallow water, high primary productivity, and intermediate sea surface temperatures. Furthermore, foraging roseate terns were associated with high sandlance abundance. By establishing direct, positive relationships among terns, prey, and habitat, this study demonstrates how common and roseate terns act as community, fisheries, and ecological indicators. These 2 species evidently provide interspecific cues to the presence of prey; therefore, the conservation and management of roseate terns depends not only on the availability of sandlance and suitable habitat, but also on the ecology of common terns.

KEY WORDS: Social facilitation · Foraging strategy · Community ecology · Prey availability · Sand lance · Distance sampling · Distribution patterns · Spatial habitat models