Foraging tactics of chick-rearing Crozet shags: individuals display repetitive activity and diving patterns over time

It is in the interest of resident and long-lived benthic foragers to learn to apply efficient foraging tactics throughout their lifetime, thus increasing their individual efficiency. To test whether individuals are capable of applying an individual-specific foraging pattern, we checked for the existence of established foraging routines. Using ventrally attached time-depth recorders, we studied the individual foraging tactics of chick-rearing Crozet shags (Phalacrocorax melanogenis, Blyth 1860), as measured by the consistency in individual daily activity patterns and diving profiles over time. Individuals displayed a fidelity to the time of first daily trip to sea and also a strong fidelity to one, two or three depth ranges day after day. We suggest foraging area fidelity, a behaviour that could help increase foraging efficiency thanks to the memorization of the bottom’s topography and the habits of its fauna, as a hypothesis for explaining some of these patterns. We propose the question of foraging area fidelity should be more specifically addressed in the future.