A year in the life of a North Atlantic seabird: behavioural and energetic adjustments during the annual cycle

Ruth E Dunn,Michael P Harris,Jonathan A Green,Francis Daunt,Sarah Wanless

doi:10.1038/s41598-020-62842-x

Ruth E Dunn, Michael P Harris + Show 3 more

Open Access

https://doi.org/10.1038/s41598-020-62842-x

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Abstract

During their annual cycles, animals face a series of energetic challenges as they prioritise different life history events by engaging in temporally and potentially spatially segregated reproductive and non-breeding periods. Investigating behaviour and energy use across these periods is fundamental to understanding how animals survive the changing conditions associated with annual cycles. We estimated year-round activity budgets, energy expenditure, location, colony attendance and foraging behaviour for surviving individuals from a population of common guillemots Uria aalge. Despite the potential constraints of reduced day lengths and sea surface temperatures in winter, guillemots managed their energy expenditure throughout the year. Values were high prior to and during the breeding season, driven by a combination of high thermoregulatory costs, diving activity, colony attendance and associated flight. Guillemots also exhibited partial colony attendance outside the breeding season, likely supported by local resources. Additionally, there was a mismatch in the timing of peaks in dive effort and a peak in nocturnal foraging activity, indicating that guillemots adapted their foraging behaviour to the availability of prey rather than daylight. Our study identifies adaptations in foraging behaviour and flexibility in activity budgets as mechanisms that enable guillemots to manage their energy expenditure and survive the annual cycle.

Highlights

During their annual cycles, animals face a series of energetic challenges as they prioritise different life history events by engaging in temporally and potentially spatially segregated reproductive and non-breeding periods
We present the first estimates of year-round daily energy expenditure (DEE) for surviving individuals in a population of free-ranging common guillemots Uria aalge and seek to understand the behavioural and energetic adaptations that they utilised in order to survive the annual cycle
Inspection of time-lapse camera data revealed that guillemots first returned to the colony after the breeding season on the 15th October but colony attendance remained low until early January (Fig. 3)

Summary

Introduction

Animals face a series of energetic challenges as they prioritise different life history events by engaging in temporally and potentially spatially segregated reproductive and non-breeding periods. Guillemots have the highest wing loading (mass per unit area of the wing) of any flying bird[14] and are central place foragers during their summer breeding seasons[15] They incur high energetic costs during the breeding period[16], these costs must remain below an optimal sustainable threshold (4 to 5 times their basal metabolic rate (BMR)6,17) to ensure reproductive success and survival. Previous studies have shown that guillemots exhibit behavioural plasticity in response to variation in the environmental conditions they encounter during the non-breeding period, with consequences for their energetic budgets and mortality Those that wintered in the Norwegian, Barents and White Seas increased their foraging effort ahead of several weeks of polar night, potentially maximising prey intake prior to this period of intense environmental constraint[20]. As with other seasonally breeding diving birds, make good models to investigate behavioural and energetic responses to seasonally varying ecological drivers

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