Annual cycles in the behaviour and energetics of North Atlantic seabirds

• Main Author: Dunn, Ruth
• Format: Text
• Language: unknown
• Published: University of Liverpool Repository 2022
• Subjects: Alca torda; fratercula; Fratercula arctica; North Atlantic; Uria aalge; uria
• Online Access: https://dx.doi.org/10.17638/03114298; https://livrepository.liverpool.ac.uk/id/eprint/3114298

Energy is the central currency that drives biological processes at every hierarchical level of life and maintaining an energetic balance is therefore integral to an animal’s survival. For iteroparous species, investigating how they manage their energy budgets throughout the annual cycle, in the face of seasonally varying intrinsic and extrinsic drivers, is critical to understanding the viability of populations. Although studying year-round energetics has previously been challenging, advances in biologging technology increasingly help to provide novel insights. Seabirds are a frequently investigated taxon within biologging studies; they are top marine predators that are often wide-ranging and many species are of high conservation concern due to a multitude of anthropogenic threats. However, despite an accumulation of knowledge regarding seabird movement and behaviour during their breeding seasons, our understanding of their year-round energetics remains fragmented. Within this thesis I therefore use a range of biologging and analytical approaches to investigate seabird behaviour and energetics throughout different key phases of the year, as well as across the entire annual cycle. Initially, using a global, multi-species, meta-analytical approach, I identify the large-scale drivers of seabird energetics during the breeding period. I demonstrate that seabird energy expenditure increases across the breeding season and also that it is higher for larger birds living at more extreme latitudes. I then focus on the North Atlantic marine ecosystem and compare the diving behaviour of common guillemots Uria aalge, razorbills Alca torda and Atlantic puffins Fratercula arctica during the period following the breeding season. Using biologging data, I identify interspecific, sex-specific and temporal differences in key dive metrics, driven by differences in body mass, post-breeding strategy and environmental conditions. Next, I combine both biologging data and statistical modelling approaches to focus on temporal changes in the behaviour and energetics of common guillemots. I illustrate that seasonal variation in thermoregulatory costs, diving activity, colony attendance and associated flight all drive guillemot energy expenditure. Finally, I identify temporal and spatial patterns in year-round body mass, subsequent susceptibility to mortality and energy gain. By examining the year-round energetics of seabirds I have therefore been able to develop a more mechanistic understanding of the links between seabird behaviour, energetics and survival in the face of seasonal environmental variability. Due to my focus on energetics, these findings have conservation and management implications; I demonstrate novel approaches to not only increase our understanding of the year-round food requirements of the world’s seabirds, but also the potential to identify times and locations throughout the year where seabirds might be susceptible to threats that may impede their survival.