Petrels are a group of seabirds that undertake an exodus from their breeding colony just prior to egg-laying, purportedly to allow the female to acquire nutrients for egg synthesis from the local environment. We studied seasonal nutrient dynamics and at-nest behaviour of northern fulmars (Fulmarus glacialis), a petrel found in the Canadian High Arctic, to evaluate the importance of pre-laying nutrient reserves to annual breeding in this species. Females and males carried 35–50% more fat when they first arrived at the colony than when they returned from their pre-laying exodus to lay their egg or initiate incubation. Fulmars spent approximately 70% of their time at the nest engaged in energetically expensive behaviours (pair-bonding, digging out and defending their nest site) during the brief period from colony arrival to departure on their pre-laying exodus. In contrast, 70% of their time at the nest was spent resting during incubation. Both nutrient reserves and behavioural data suggest that High Arctic fulmars require large endogenous reserves prior to egg-laying to fuel their energetically costly activities during the arrival-to-exodus period.

Nomenclature: Hatch & Nettleship, 1998.