ORIGINAL ARTICLE Nest shelter predicts nesting success but not nesting phenology or parental behaviors in high arctic Northern Fulmars Fulmarus glacialis Mark L. Mallory • Mark R. Forbes Received: 17 January 2010 / Revised: 30 April 2010 / Accepted: 15 June 2010 / Published online: 13 July 2010 Ó Her Majesty the Queen in Right of Canada 2010 Abstract The physical characteristics of nest sites are thought to influence both the outcome of breeding attempts and breeding behavior in colonial seabirds. We examined the relationship between nest shelter in breeding Northern Fulmars (Fulmarus glacialis), at the remote Cape Vera colony on Devon Island, Nunavut, Canada, and timing of nesting, reproductive success, and the amounts of time parents spent in different behaviors. Fulmars nesting in sheltered caves experienced lower predation pressure and produced more chicks than Fulmars nesting on exposed ledges. Experimental nests at such cave sites also had lower depredation rates than experimental nests on ledges. There were no differences between Fulmars at different nest types in their laying dates, incubation shifts, incuba- tion period, or the amount of time they allocated to behaviors at the nest. Parents with nests at sheltered cave sites appeared to have higher thermoregulatory costs. We postulate parental experience is more important than costs associated with physical characteristics of nest sites in influencing behavior of incubating Fulmars. Keywords Arctic Á Predation Á Weather Á Incubation Á Fulmarus glacialis Introduction Breeding birds must balance use of their time and energetic stores to successfully reproduce, while maintaining their own body condition in order to evade predators, avoid disease, and survive to reproduce in the following years (Trivers 1972; Montgomerie and Weatherhead 1988). Among colonial seabirds, analyses of time-activity budgets during breeding have focused on sex-specific roles on and off the nest (e.g., Hatch 1990a; Weimerskirch 1995; Stahl and Sagar 2006), but less has been reported on how birds apportion time while at the nest site (but see Grant et al. 1982; Maxson and Bernstein 1984; Verspoor et al. 1987). Clearly behavior and reproductive success can vary with nest location in a seabird colony (e.g., Gaston and Nettleship 1981; Pierotti 1982; Gaston and Elliot 1996), and behavioral factors such as breeding synchronization, incubation scheduling, and predator defense typically cor- relate with reproductive success (Coulson 2002; Hamer et al. 2002). Moreover, the physical characteristics of a nest site can influence nest microclimate (Kim and Monaghan 2005a, b), levels of disturbance from conspecifics (Kim and Monaghan 2005a), and predation risk (Gaston and Elliot 1996; Gilchrist and Gaston 1997), and thereby influence parental behavior at the nest. For example, parents at highly visible sites may spend more time vigilant or defending their nest against conspecific intruders or patrolling predators, potentially reducing both energy stores and the time spent incubating their clutch (Drent 1975; Hatch and Nettleship 1998). We studied the relationship between nest site charac- teristics and time allocated to different behaviors by Northern Fulmars (Fulmarus glacialis) breeding in the Canadian high arctic. Age, breeding experience, and mar- ine productivity are the principal factors influencing annual Communicated by P. H. Becker . M. L. Mallory (&) Canadian Wildlife Service, Box 1714, Iqaluit, NU X0A 0H0, Canada e-mail: mark.mallory@ec.gc.ca M. L. Mallory Á M. R. Forbes Department of Biology, Carleton University, Ottawa, ON K2S 5B6, Canada 123 J Ornithol (2011) 152:119–126 DOI 10.1007/s10336-010-0556-2