|
Vol. 53, 2014
Resource partitioning between incubating and chick-rearing
brown boobies and red-tailed tropicbirds on Christmas Island
Joan
Navarro1*, Rocio Moreno2,3, Lena Braun4,
Carola Sanpera3 and Janos C Hennicke4,5
1Institut
de Cičncies del Mar (ICM-CSIC), P. Marítim de la Barceloneta 37-49,
Barcelona 08003, Spain
2British Antarctic Survey, Natural Environment
Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK
3Departament de Biologia Animal (Vertebrats), Facultat
de Biologia, Universitat de Barcelona, Av. Diagonal 645, Barcelona
08028, Spain
4Department of Ecology and conservation, Biocentre
Grindel, University of Hamburg, Martin-Luther-King-Platz 37, Hamburg
20146, Germany
5Centre d’Études Biologiques de Chizé, UPR 1934 du
CNRS, Villiers-en-Bois 79360, France
Abstract
Background: In oligotrophic
tropical marine environments, the main mechanism explaining the
coexistence of sympatric seabirds is segregation by habitat or
segregation by prey within the same habitat. Both types of segregation
can play a role during the breeding season due to different constraints
associated with different phases of the breeding cycle. By using stable
isotope analyses, we investigated intra- and interspecific foraging
segregation in two tropical seabird species, the red-tailed tropicbird Phaeton rubricauda and the brown booby Sula leucogaster, breeding sympatrically
on Christmas Island, Indian Ocean. We compared isotopic values of δ13C
and δ15N in blood
from incubating and chick-rearing adults of both species.
Results: The results showed small but
significantly interspecific and intraspecific differences in δ13C
and δ15N values. Differences in δ13C values
suggest spatial segregation in the main foraging grounds between the
two species during the breeding season as well as between incubating
and chick-rearing brown boobies. In contrast, red-tailed tropicbirds
probably exploited similar foraging habitats during both breeding
stages. δ15N values did not indicate diet-related
differences, neither within nor between species, suggesting a highly
opportunistic feeding behavior to cope with the limited prey available
in the oligotrophic marine environment.
Conclusions: Competition for prey
in breeding red-tailed tropicbirds and brown boobies seems to be
reduced by spatial segregation enabling both species to successfully
reproduce in sympatry in an oligotrophic tropical marine environment.
Key words: Feeding segregation; Stable
isotope analysis; Tropical ecosystems; Seabirds.
*Correspondence: E-mail: joan@icm.csic.es
|
