Habitat preferences of Phoebetria albatrosses in sympatry and allopatry

Aim

Competition is often proposed to drive niche segregation along multiple axes in speciose communities. Understanding spatial partitioning of foraging areas is particularly important in species that are constrained to a central place. We present a natural experiment examining variation in habitat preferences of congeneric Southern Ocean predators in sympatry and allopatry. Our aim was to ascertain consistency of habitat preferences within species, and to test whether preferences changed in the presence of the congener.

Location

Southern Hemisphere.

Taxon

Multiple colonies of both species within the genus Phoebetria (sooty albatrosses).

Methods

The two Phoebetria albatrosses breed on islands located from ~37–55°S – sooty albatrosses (P. fusca) in the north and light-mantled albatrosses (P. palpebrata) in the south – with sympatric overlap at locations ~46–49°S. We analysed GPS and PTT tracks from 87 individuals and multiple remotely sensed environmental variables using GAMs, to determine and compare the key factors influencing habitat preference for each species at each breeding colony.

Results

While foraging habitat preferences are consistent in light-mantled albatrosses, there is divergence of preferences in sooty albatrosses depending on whether they are in sympatry with their congener or in allopatry.

Main Conclusions

This study represents the most comprehensive work on this genus to date and highlights how habitat preferences and behavioural plasticity may influence species distributions under different competitive conditions.