Foraging ecology during nesting influences body size in a pursuit-diving seabird

Abstract

Causes and consequences of differences in seabird foraging strategies between breeding colonies are not well understood. We tested whether body size of a pursuit-diving seabird, the thick-billed murre Uria lomvia, differs between breeding colonies and, if so, how size differences can be understood in the context of differences in foraging behavior, habitat use, and breeding performance. We measured adult murres over 3 seasons (2008 to 2010) at 2 of the Pribilof Islands, St. Paul and St. George, located on the continental shelf of the Bering Sea at different distances from the shelf break. Body mass and size were positively associated with deep diving and negatively associated with long flights, suggesting morphology influences foraging and commuting efficiency. Murres from St. Paul (farther from the shelf break) were larger than those from St. George (nearer the shelf break), foraged exclusively in the middle shelf domain, made deep dives during daylight, and fed on larger benthic prey. In contrast, smaller murres from St. George commuted greater distances to beyond the shelf break, made shallow dives at night, and fed on smaller, high-energy, schooling, vertical-migrating prey. Both foraging strategies resulted in similar chick-feeding rates and fledging success. The largest and the smallest murres experienced less stress during breeding compared to intermediate-sized murres, suggesting divergent selection for body size between islands. N esting murres, as central-place foragers, may experience strong selection pressure on body size and other adaptive traits that reflect differences between breeding colonies in foraging ecology and the acquisition of resources for reproduction.

Breeding density, fine‐scale tracking, and large‐scale modeling reveal the regional distribution of four seabird species

“…, Paredes et al. ). Furthermore, tracking data record the presence of animals but not their absence (Aarts et al.…”

“…This is partly because tracking data violate many of the assumptions inherent to conventional parametric models (reviewed by Turchin 1998, Aarts et al 2008, Wakefield et al 2009). Repeat observations on individuals (typically 10 2 -10 4 locations/individual in seabird studies) tend to be spatiotemporally autocorrelated and the movements of individuals drawn from the same colony may be dependent on one another due to public information transfer and cultural and genetic divergence (Wakefield et al 2013, Paredes et al 2015. Furthermore, tracking data record the presence of animals but not their absence (Aarts et al 2012).…”

Resource partitioning between sympatric seabird species increases during chick‐rearing

“…It has been shown that body size may play an important role in shaping the foraging decisions of murres breeding on the same colonies (Paredes et al. ). For instance, large‐bodied individuals (such as daytime diving TBMU; Fig.…”

Foraging segregation of two congeneric diving seabird species breeding on St. George Island, Bering Sea

“…TBMU populations exhibit various behavioral patterns, which may be due to interregional differences in morphology . TBMUs from St. Paul Island with larger body mass and wing loading performed shorter foraging trips and deeper dives, whereas TBMUs from St. George Island with smaller body mass and wing loading performed longer foraging trips and shallower dives Paredes et al, 2015). Thus, segregation patterns between COMUs and TBMUs may differ among regions partly because their morphology differs at a regional scale.…”

“…A few studies have revealed inter-or intraspecific differences in the foraging behavior of COMUs and TBMUs from the aspects of morphology and breeding ecology (Barger et al, 2016). Paredes et al (2015) showed that, within TBMU colonies, smaller individuals tended to fly longer distances and dive shallower, whereas the opposite pattern was observed in larger individuals, likely reflecting their body mass and wing loading. TBMUs have also shown intersexual differences in the diel patterns of diving behavior (Jones et al, 2002;Paredes et al, 2008); however, the presence of such habitat partitioning appears to vary by geographical region (Elliott et al, 2010).…”