Feather isotopes can detect seasonal and individual differences on what and where albatrosses and petrels feed at sea

Audrey Jaeger of the Centre d'Etudes Biologiques de Chizé (CEBC) in France and colleagues have recently published in the journal Marine Ecology Progress Series a study of four ACAP-listed species breeding on the Crozet Islands in the southern Indian Ocean that uses stable isotope of body feathers to assess trophic niche widths.

The paper's abstract follows:

"Niche variation is a widespread phenomenon that has important implications for ecological interactions and conservation biology, but few studies have quantified the trophic niche width (TNW) and its within- and between-individual components.  We used stable isotopes of body feathers to investigate seasonal isotopic niche changes of 4 southern procellariiforms and the level to which individuals are specialised relative to their population within each season.

δ13C and δ15N values of chicks and adults indicated a well-defined trophic segregation within the seabird assemblage during both the breeding and poorly known moulting (inter-nesting) periods, and they underlined marked species-specific seasonal changes.  One species (Light-mantled Sooty Albatross) remained within the Southern Ocean both during breeding and body feather moult, while the 3 others migrated either to oceanic subtropical waters (Wandering and Sooty Albatrosses) or high isotopic marine areas (e.g. productive neritic waters; White-chinned Petrel) during the moulting period.

Isotopic variances and TNW were generally low, indicating that birds belong to isotopic specialist populations within a given period.  Variances and TNW were larger for White-chinned Petrel chicks and Light-mantled Sooty Albatross adults, respectively, indicating isotopic generalist populations and revealing 2 new foraging behaviours.  Individual White-chinned Petrel chicks segregated by their feather isotopic signatures, thus indicating individual/pair specialisation of parent birds during the chick-rearing period.  The Light-mantled Sooty Albatross population included mostly isotopic generalist individuals during the moulting period, with individuals using different habitats and diets.

The study highlights the utility of feather isotopic signature for determining TNW and points out the necessity to develop such new approaches to better depict niche variations at both population and individual levels."

To view a listing of the many CEBC published and in-press scientific publications on ACAP-listed albatrosses and petrels arranged annually since 1964 visit http://www.cebc.cnrs.fr/publications/sous_presse.htm.  Postgraduate theses since 1965 are also listed.  Quite a resource!

Reference:

Jaeger, A., Connan, M., Richard, P. & Cherel, Y. 2010.  Use of stable isotopes to quantify seasonal changes of trophic niche and levels of population and individual specialisation in seabirds.  Marine Ecology Progress Series 401: 269-277. (click here for the PDF).

John Cooper. ACAP Information Officer, 30 October 2010

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