ADDISON, BA*; KITAYSKY, AS; HIPFNER, JM; Simon Fraser University; University of Alaska – Fairbanks; Simon Fraser University and Canadian Wildlife Service: Is parental investment by rhinoceros auklets (Cerorhinca monocerata) fixed or flexible?

Parental investment strategies lie on a continuum between two extreme strategies of fixed versus flexible effort. In a fixed effort strategy, a parent allocates a fixed amount of its time or energy budget to the current reproductive attempt, and so the chick pays the cost when food conditions are poor. In a flexible effort strategy a parent allocates time and energy to the reproductive effort to meet the demands of the chick, so the parent pays the cost of poor food conditions. We studied Rhinoceros Auklets Cerorhinca monocerata breeding on Triangle Island, British Columbia, in 2003, a poor food year, and 2004, a good food year. We measured body condition and physiological condition, indexed by corticosterone stress response of parents, and growth rates and fledging parameters of their chicks, to determine who was paying the cost when food conditions were poor. Body condition index of parent Rhinoceros Auklets was not different in the two study years. Baseline corticosterone was marginally higher and corticosterone response significantly higher in 2003 than 2004. Chick fledge mass was lower in 2003 than in 2004. This indicates that chicks and parents bear some cost of poor food conditions, though parents appear to reserve some investment, as body condition was not compromised. Rhinoceros Auklets are less willing to increase investment in the current reproductive effort, compared to some other seabird species.