Morphological versus molecular identification of Sooty ( Phoebetria fusca) and Light-mantled ( P. palpebrata) albatross chicks.

The two fuliginous albatross species, Phoebetria fusca (the Sooty albatross, SA) and P. palpebrata (the Light-mantled albatross, LMA), are found breeding close to each other on the Prince Edward Islands (Southern Ocean). Adults of these two species are easy to identify in the field, but the chicks are difficult to distinguish on the basis of external morphology, especially at very young ages. Many ecological studies involve sampling of chicks as well as adults, and accurate field identification of chicks is thus crucial. Traditionally, the extent of the ring of pale feathers around the eye (eye-ring) has been used to identify the fledglings. The aim of our study was to investigate the utility of characters associated with the eye-ring (extent, measured as an angle, and colour) for the identification of Phoebetria chicks. This was achieved by comparison of identifications based on morphology, with positive identifications based on DNA sequence data from the mitochondrial cytochrome b gene. We confirm the value of morphological criteria in distinguishing LMA and SA chicks, and this technique appears to be accurate in the majority of cases (>80%). However, we recommend using molecular identification for borderline cases (angle of the eye-ring measuring between 85 and 95°) if independent confirmation of chick identity cannot be obtained (e.g. via observed feeding interaction with an adult). [ABSTRACT FROM AUTHOR]