Spatial variation in vital rates and population growth of thick-billed murres in the Atlantic Arctic

M Frederiksen,Y Kolbeinsson,E Lorentzen,Aj Gaston,Kh Elliott,Tl Thórarinsson,Fr Merkel,Np Huffeldt,Jf Linnebjerg,S Descamps,H Strøm

doi:10.3354/meps13823

Abstract

Understanding spatiotemporal variation in vital rates and population growth rates is a central aim of population ecology, and is critical to conservation of migratory species where different populations may spend the non-breeding season in sometimes widely separated areas. However, estimating those parameters and identifying the underlying drivers of variation for species migrating to remote areas is challenging. The thick-billed murre Uria lomvia is a colonial seabird with a pan-Arctic distribution. Previous studies have documented large-scale spatial variation in population growth in the species’ Atlantic range, with eastern populations declining and western populations being stable, and suggested that this variation was linked to conditions in the wintering areas. We analyse variation in breeding success and adult survival from colonies throughout the Atlantic range, construct region-specific stochastic population models, and compare model predictions to observed colony growth rates. Breeding success was uniformly high in Greenland and Iceland, lower and more variable in Spitsbergen, Bjørnøya and Hudson Bay, and low at Jan Mayen. Adult survival was average or high in all colonies during the 2010s. Observed colony growth rates were lower than modelled growth rates for most populations. This suggests that pre-breeding survival or breeding propensity must have been lower than assumed in many of these populations. Low pre-breeding survival could be linked to poor feeding conditions in fall and winter, possibly influenced by large-scale oceanographic variation. Our results support the idea that seabird populations not subject to breeder mortality due to anthropogenic causes are regulated mainly through variation in pre-breeding survival.

Highlights

Most animal species show extensive spatial variation in vital rates, most importantly survival and reproductive output, and rate of population change or growth (Bjørnstad et al 1999, Frederiksen et al 2005)
We suggest that variation in vital rates and population growth between seabird populations wintering in different areas would support Lack’s view
We have collated and analysed the most extensive data set to date on spatiotemporal variation in demography of thick-billed murres

Summary

Introduction

Most animal species show extensive spatial variation in vital rates, most importantly survival and reproductive output, and rate of population change or growth (Bjørnstad et al 1999, Frederiksen et al 2005). Such variation occurs on scales ranging from very local (Tavecchia et al 2008, Sanz-Aguilar et al 2009) to global (Irons et al 2008, Suryan et al 2009). Interannual variability in vital rates or population growth is synchronised over relatively large spatial scales (Liebhold et al 2004), while others show extensive spatial variation with little or no synchrony (Cayuela et al 2020, Descamps et al 2020). Conditions on the wintering grounds may have a strong impact on survival and lead to differences and similarities (e.g. synchrony) among populations (Gaston 2003, Reneerkens et al 2020)

Methods

Results

Conclusion