Does location really matter? An inter-colony comparison of seabirds breeding at varying distances from productive oceanographic features in the Bering Sea

Abstract

a b s t r a c tCentral place foragers, such as breeding seabirds, need to commute between their nests and foraging grounds, thus close proximity of the breeding colony to productive oceanographic features might be beneficial for seabird reproduction. We tested this hypothesis by investigating the at-sea foraging and breeding behavior of thick-billed murres (Uria lomvia) nesting at three colonies (Bogoslof, St. Paul, and St. George Islands) in the Bering Sea located at different distances from the productive continental shelf-break. We found that distances to feeding areas differed only during night trips among colonies. St. Paul murres foraged entirely on the shelf, whereas St. George murres commuted to the continental shelf-break at night and foraged on the shelf during the day. Bogoslof murres foraged in oceanic waters in close proximity to the colony. Murres breeding at the both Pribilof colonies spent less time attending nests and had higher levels of stress hormone corticosterone compared to murres breeding at Bogoslof, although chick-provisioning rates and fledging success were similar among the three colonies. Lower nest attendance and higher corticosterone suggest lower food availability in the Pribilof domain compared to the Bogoslof region. Murres breeding at the Pribilofs used different foraging strategies to buffer effects of food shortages on their reproduction: flight costs associated with longer distance night trips at St. George were presumably balanced by benefits of higher density and/or more lipid rich prey in the continental shelf-break regions, whereas the additional distance of St. Paul from the continental shelf-break may have outweighed any energetic gain. Murres exhibited a remarkable degree of plasticity of foraging strategies in response to changes in their food availability, but the breeding success of murres did not reflect either food limitations or the colony proximity to productive oceanographic features.

Telomere length is a strong predictor of foraging behavior in a long‐lived seabird

“…We also included sex in our analyses as it is a common driver of foraging behaviors in many taxa (Aho et al 1997, Codding et al 2011) including seabirds (e.g., Weimerskirch et al 1997, Welcker et al 2009). Adult male murres have longer telomeres than females (Young et al 2013), which follows the pattern seen in other bird species (Horn et al 2011). In murres, diving patterns differ by sex (Jones et al 2002), and in the Common Murre (Uria aalge), females provide more food to the chick, perhaps because males invest in themselves during the nestling phase, saving chick investment for the extended weeks of post-fledging care provided only by the male (Thaxter et al 2009).…”

“…Murres, like most long-lived seabirds, show higher TL in chicks than adults (chicks: 3564 6 82 bp; adults: 3441 6 27 bp) and slow variable rates of change in adult birds, where loss rate in a cross-sectional sample of adults was 5.2 6 10 bp per year (Young et al 2013). Longitudinal changes in TL in murres indicate that colony-specific environmental conditions may play a mediating role in whether birds gain, lose, or maintain TL (Young et al 2013;Young et al, unpublished manuscript). Habitat choice (high or low quality) can affect TL losses (Angelier et al 2013), and exposure to stress, simulating the decreased food availability of poor environmental conditions, also exacerbates TL loss (Schultner et al 2014).…”

“…1). This study takes advantage of a gradient of colony-specific environmental conditions and habitat qualities (Byrd et al 2008, Harding et al 2013Young et al, unpublished manuscript). Previous work has characterized the study system during our study years (2008 and 2009) as a ''food-rich colony,'' Bogoslof; a ''food-poor colony,'' St. Paul; and one which presents intermediately, St. George; hereafter ''good,'' ''poor,'' and ''middling'' (Harding et al 2013;Young et al, unpublished manuscript).…”

“…This study takes advantage of a gradient of colony-specific environmental conditions and habitat qualities (Byrd et al 2008, Harding et al 2013Young et al, unpublished manuscript). Previous work has characterized the study system during our study years (2008 and 2009) as a ''food-rich colony,'' Bogoslof; a ''food-poor colony,'' St. Paul; and one which presents intermediately, St. George; hereafter ''good,'' ''poor,'' and ''middling'' (Harding et al 2013;Young et al, unpublished manuscript). These colony differences are also reflected in Thick-billed Murre population trends and stress hormone patterns; Bogoslof is an increasing colony with low stress levels, St. Paul is declining or stabilizing after a crash and has high stress levels, and St. George is stable after recovery from a crash with middling stress levels (Byrd et al 2008, Dragoo et al 2012).…”

“…Adult Thick-billed Murres were sampled in five colony-years (e.g., St. (Harding et al 2013). Year differences were minimal and are not considered here, as more sample years would be needed to detect differences due to interannual trends.…”