Abstract
Technical development such as radiotelemetry, data logger and stable isotope analyses have enabled studies of individual variation in foraging ecology of seabirds. Individual variation in dive depth, foraging site, diet and foraging habitat are often observed in Phalacrocoracidae. Individuals feed solitarily but sometimes join large foraging groups. Some birds migrate but others are resident. Individual birds show high flexibility in foraging behaviour according to food availability. Thus foraging site fidelity and flexible foraging behaviour are both important aspects of cormorant foraging ecology. The stable isotope ratio in appropriate tissues gives us useful information on the food cormorants ate during certain time windows. To understand individual-based foraging strategies and population dynamics, and also to provide adequate plans for conservation and management of cormorants, further research is necessary on the factors determining individual variation in foraging ecology.
