Spatial distribution and ecological niches of non-breeding planktivorous petrels.

Joan Navarro,Ruth Brown,Laura Cardador,Richard A Phillips

doi:10.1038/srep12164

Abstract

According to niche theory, mechanisms exist that allow co-existence of organisms that would otherwise compete for the same prey and other resources. How seabirds cope with potential competition during the non-breeding period is poorly documented, particularly for small species. Here we investigate for the first time the potential role of spatial, environmental (habitat) and trophic (isotopic) segregation as niche-partitioning mechanisms during the non-breeding season for four species of highly abundant, zooplanktivorous seabird that breed sympatrically in the Southern Ocean. Spatial segregation was found to be the main partitioning mechanism; even for the two sibling species of diving petrel, which spent the non-breeding period in overlapping areas, there was evidence from distribution and stable isotope ratios for differences in habitat use and diving depth.

Highlights

According to niche theory, mechanisms exist that allow co-existence of organisms that would otherwise compete for the same prey and other resources
We investigated for the first time the potential ecological isolating mechanisms that might operate during the non-breeding period of four small (120–200 g), very abundant zooplanktivorous seabirds - blue petrel (Halobaena caerulea), Antarctic prion (Pachyptila desolata), common diving petrel (Pelecanoides urinatrix) and South Georgian diving petrel (P. georgicus) - which breed in sympatry on islands in the Southern Ocean
Antarctic prions were distributed in Atlantic and, to a lesser extent, Pacific waters, but at lower latitudes than blue petrels (Fig. 1)

Summary

Introduction

Mechanisms exist that allow co-existence of organisms that would otherwise compete for the same prey and other resources. We investigate for the first time the potential role of spatial, environmental (habitat) and trophic (isotopic) segregation as niche-partitioning mechanisms during the non-breeding season for four species of highly abundant, zooplanktivorous seabird that breed sympatrically in the Southern Ocean. Spatial segregation was found to be the main partitioning mechanism; even for the two sibling species of diving petrel, which spent the non-breeding period in overlapping areas, there was evidence from distribution and stable isotope ratios for differences in habitat use and diving depth. We investigated for the first time the potential ecological isolating mechanisms that might operate during the non-breeding period of four small (120–200 g), very abundant zooplanktivorous seabirds - blue petrel (Halobaena caerulea), Antarctic prion (Pachyptila desolata), common diving petrel (Pelecanoides urinatrix) and South Georgian diving petrel (P. georgicus) - which breed in sympatry on islands in the Southern Ocean. Environmental (habitat) and trophic niches by analysing tissue stable isotope ratios, and integrating distribution of birds tracked using miniaturized geolocators with remotely-sensed oceanographic variables

Methods

Results

Conclusion