abstract
A census of Kerguelen terns Sterna vigata at Marion Island and Prince Edward Islands was conducted during August and September 1984. The population size was estimated at 25-30 breeding pairs, of which 20 pairs were on Prince Edward Island. Kerguelen terns were found mostly on the sheltered southeast coast of Prince Edward Island, whereas on Marion Island they were found only on the exposed west and north coasts. The absence of Kerguelen terns from apparently suitable habitat on Marion Island, coupled with the small number of first-year and immature birds counted, suggests that the population at Marion Island may be decreasing. Foraging occurred primarily by dipping, with occasional surface plunge dives. Most foraging occurred at sea, either over beds of Macrocystis kelp or over the surf zone.