Multiple-colony winter habitat use by murres Uria spp. in the Northwest Atlantic Ocean: implications for marine risk assessment

Abstract

Limited knowledge of year-round seabird distributions hinders efforts to assess consequences of anthropogenic threats and climate-induced changes in the marine environment. In particular, there is urgent need to understand how populations from different breeding colonies share and partition ocean habitat. Using geolocators, we identified winter habitat use patterns of 115 adult murres Uria spp. from 7 colonies, spanning the eastern Canadian coast from the high Arctic to Newfoundland, during 2007 to 2010. Thick-billed murres U. lomvia dispersed throughout the region (Davis Strait, Labrador Sea, Orphan Basin, Grand Bank) with 0 to 45% overlap of core wintering areas (50% kernel home range) among breeding populations. Common murres U. aalge concentrated on the Grand Bank and Orphan Basin, with 50 to 67% overlap among breeding populations. For both species, most individuals (up to 70%) wintered offshore, in shelf (≤500 m deep) and oceanic zones (> 500 m); fewer than one-third (30%) of individuals used nearshore zones (≤50 km to shore). Tracked common murres representing > 80% of the eastern Canadian breeding population converged in winter in areas of high risk from hydrocarbon exploration and extraction activity. In contrast, tracked thick-billed murres, representing ~34% of the eastern Canadian population, dispersed over a larger area and displayed more variable wintering strategies. Thus population vulnerability to spatially constrained risks may be greater for common than thick-billed murres. Populations from several colonies of both species converged on the Grand Bank and Orphan Basin, with the implications for each breeding population depending on its particular dispersal pattern. We demonstrate the utility of tracking data for highlighting areas of risk, and improving the targeting of broad-scale marine conservation efforts.

Individual-level Variation and Higher-level Interpretations of Space Use in Wide-ranging Species: An Albatross Case Study of Sampling Effects

“…Commonly in multi-colony tracking studies, the size of the areas used and the degree of at-sea spatial segregation among seabird colonies are delineated by a pooled KDE from a sample of tracked individuals from each group. The size of pooled KDE 50 or 95% contours are quantified and compared, and the degree of overlap between groups is calculated (e.g., Young et al, 2009;Frederiksen et al, 2012;Thiebot et al, 2012;McFarlane Tranquilla et al, 2013;Ratcliffe et al, 2014). However, without consideration of individual variation within an available dataset, these higher-level inferences can be inadvertently misleading.…”

“…For black-legged kittiwakes (Frederiksen et al, 2012) and murres (Uria spp., McFarlane Tranquilla et al, 2013), the overwinter movements of tracked individuals have been taken to represent all of their colony members proportional to the colony's breeding population, thereby "distributing" members among specified regions of interest. Pooled KDE 50% contours generated from 15 or fewer individuals were taken to represent 11 of 16 kittiwake study colonies, and three of those colonies were represented by 5-7 tracked birds (Frederiksen et al, 2012).…”

“…Defining period-specific space use can help to identify the source or severity of common or distinct threats posed at different periods in the annual cycle for a species, and for further sub-groups divided by for example age-class (e.g., Péron and Grémillet, 2013;Riotte-Lambert and Weimerskirch, 2013;Gutowsky et al, 2014a), or sex (e.g., Phillips et al, 2004;Hedd et al, 2014). At the colony level, individual-based tracking data have been used to discern period-and colony-specific space use and potential associated impacts for population dynamics for a variety of seabird species (e.g., Young et al, 2009;Catry et al, 2011;Gaston et al, 2011;Wakefield et al, 2011;Frederiksen et al, 2012;McFarlane Tranquilla et al, 2013).…”

“…from the same colony during breeding), and the practice has since become commonplace. Some recent examples include the use of pooled KDE to compare space use between different annual periods for a species and colony (e.g., Robertson et al, 2014), different species from the same colony (e.g., Linnebjerg et al, 2013), different colonies of the same species (e.g., Young et al, 2009;Thiebot et al, 2011), and different species and colonies (e.g., McFarlane Tranquilla et al, 2013Tranquilla et al, , 2015Ratcliffe et al, 2014). …”

Mortality of Migratory Birds from Marine Commercial Fisheries and Offshore Oil and Gas Production in Canada

“…al 2011, McFarlane Tranquilla et al 2013 and kittiwakes (Frederiksen et al 2012). Oiled murres and Dovekies (Alle alle), the species most susceptible to oil pollution, have been recorded in small numbers at offshore oil platforms .…”