Thermodynamic modelling predicts energetic bottleneck for seabirds wintering in the northwest Atlantic

Abstract

SUMMARYStudying the energetics of marine top predators such as seabirds is essential to understand processes underlying adult winter survival and its impact on population dynamics. Winter survival is believed to be the single most important life-history trait in long-lived species but its determinants are largely unknown. Seabirds are inaccessible during this season, so conventional metabolic studies are extremely challenging and new approaches are needed. This paper describes and uses a state-of-the-art mechanistic model, Niche Mapper TM , to predict energy expenditure and food requirements of the two main seabird species wintering in the northwest Atlantic. We found that energy demand increased throughout the winter phase in both species. Across this period, mean estimated daily energy requirements were 1306 kJ day -1 for Brünnich's guillemots (Uria lomvia) and 430 kJ day -1 for little auks (Alle alle) wintering off Greenland and Newfoundland. Mean estimated daily food requirements were 547 g wet food day -1 for Brünnich's guillemots, and 289 g wet food day -1 for little auks. For both species and both wintering sites, our model predicts a sharp increase in energy expenditure between November and December, primarily driven by climatic factors such as air temperature and wind speed. These findings strongly suggest the existence of an energetic bottleneck for North Atlantic seabirds towards the end of the year, a challenging energetic phase which might explain recurrent events of winter massmortality, so called 'seabird winter wrecks'. Our study therefore emphasizes the relevance of thermodynamics/biophysical modelling for investigating the energy balance of wintering marine top predators and its interplay with survival and population dynamics in the context of global change.

Little auks buffer the impact of current Arctic climate change

“…6). There was nonetheless substantial interannual variability in adult survival especially at KH, strongly suggesting that this variable might also be driven by events occurring outside of the breeding season (Fort et al 2009 …”

Geographic and seasonal variability in the isotopic niche of little auks

“…Williams et al 2008), and modelling has improved our knowledge of seabird winter energetics (e.g. Fort et al 2009). These studies are nonetheless often restricted temporally or spatially, thereby ignoring potential environmental variability, which may affect strategies across individuals and populations (Grémillet & Boulinier 2009).…”

Distinguishing offshore bird hunting from beach scavenging in archaeological contexts: The value of modern beach surveys

“…Various experiments, including tethering tests (Ford et al 1991) and drifter studies (e.g. Camphuysen 1989), have tested the effects of the ocean on carcass sinking times and recovery on beaches; these factors impact the number and preservation of birds that wash up onshore.…”

“…While scavenged carcasses are often assumed to be primarily useful as a source of feathers or bones for tools (Eda et al 2015;Lyman 2003;Schalk 2003), wrecks may have also been valuable sources of meat. Common to all monitored shorelines, wrecks are most predictable during the post-breeding and winter months when relatively poor body condition and degrading environmental conditions push many individuals beyond their capabilities (Fort and Gremillet 2009). Of import to Minard occupants, wrecks typically deliver large numbers of intact, relatively fresh carcasses, occasionally numbering in the tens of thousands (Camphuysen et al 1999;Harris and Wanless 1996;Piatt and VanPelt 1997).…”