Dynamic oceanography determines fine scale foraging behavior of Masked Boobies in the Gulf of Mexico

PLoS One. 2017 Jun 2;12(6):e0178318. doi: 10.1371/journal.pone.0178318. eCollection 2017.

Abstract

During breeding, foraging marine birds are under biological, geographic, and temporal constraints. These contraints require foraging birds to efficiently process environmental cues derived from physical habitat features that occur at nested spatial scales. Mesoscale oceanography in particular may change rapidly within and between breeding seasons, and findings from well-studied systems that relate oceanography to seabird foraging may transfer poorly to regions with substantially different oceanographic conditions. Our objective was to examine foraging behavior of a pan-tropical seabird, the Masked Booby (Sula dactylatra), in the understudied Caribbean province, a moderately productive region driven by highly dynamic currents and fronts. We tracked 135 individuals with GPS units during May 2013, November 2013, and December 2014 at a regionally important breeding colony in the southern Gulf of Mexico. We measured foraging behavior using characteristics of foraging trips and used area restricted search as a proxy for foraging events. Among individual attributes, nest stage contributed to differences in foraging behavior whereas sex did not. Birds searched for prey at nested hierarchical scales ranging from 200 m-35 km. Large-scale coastal and shelf-slope fronts shifted position between sampling periods and overlapped geographically with overall foraging locations. At small scales (at the prey patch level), the specific relationship between environmental variables and foraging behavior was highly variable among individuals but general patterns emerged. Sea surface height anomaly and velocity of water were the strongest predictors of area restricted search behavior in random forest models, a finding that is consistent with the characterization of the Gulf of Mexico as an energetic system strongly influenced by currents and eddies. Our data may be combined with tracking efforts in the Caribbean province and across tropical regions to advance understanding of seabird sensing of the environment and serve as a baseline for anthropogenic based threats such as development, pollution, and commercial fisheries.

MeSH terms

  • Animals
  • Appetitive Behavior*
  • Birds* / physiology
  • Breeding
  • Caribbean Region
  • Ecosystem
  • Feeding Behavior
  • Female
  • Gulf of Mexico
  • Male
  • Nesting Behavior
  • Oceanography
  • Seasons

Grants and funding

This study was funded by the United States Fish and Wildlife Service, grant #2008691 (www.fws.gov, awarded to PGRJ), the Society for the Conservation and Study of Caribbean Birds (www.scscb.org, awarded to AV), and the Sacramento Zoo Conservation Fund Small Grants Program (www.saczoo.org, awarded to CLP). The South Carolina Cooperative Fish and Wildlife Research Unit is supported by the South Carolina Department of Natural Resources, Clemson University, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.