Seasonal variations in migration strategy of a longdistance Arctic-breeding seabird

Y Seyer,Jf Therrien,N Lecomte,G Gauthier,J Bêty

doi:10.3354/meps13905

Abstract

Long-distance migratory seabirds need to adjust their migration strategy according to internal (breeding, molting) and external factors (seasonality, resource availability). Time-minimizing strategies are common during spring migration to arrive at the optimal time to breed. We studied the annual movements and migration strategy of the long-tailed jaegerStercorarius longicaudus, a small arctic-nesting seabird. First, we documented year-round movements (routes, wintering sites) of male and female jaegers breeding in the Canadian Arctic. We then compared their migration strategies between seasons (phenology, stopover use, travel distance, speed) to determine whether they adopt a time-minimizing strategy in spring. Over 6 yr, we collected 43 tracks from geolocators deployed on Bylot and Igloolik Islands. Jaegers departed the breeding site over a 5 wk period and traveled on average 32375 km (round trip) before returning to breed, one of the longest documented migrations on Earth. Birds used a major stopover area east of the Grand Banks of Newfoundland in spring and fall, and wintered in high marine productivity areas of the South Atlantic. Unexpectedly, the spring migration was 40% longer and 32% slower than in fall, and birds increased their time spent on water (foraging and/or resting) by 61%. A time-minimizing strategy in fall may help to reach the wintering site rapidly and start molting early. In spring, a fly-and-forage strategy seems to be adopted to increase foraging effort, probably for the accumulation of body reserves before breeding and in anticipation of unfavorable conditions that may prevail at arrival on their arctic breeding site.

Highlights

Migratory seabirds can travel long distances across the planet, connecting distant ecosystems and exposing themselves to a diversity of environmental conditions and resources along the way
Individuals are expected to complete their spring migration as fast as possible, given constraints on flying speed and energy acquisition rate. Such a time-minimization strategy is commonly thought to play a major role during the pre-breeding migration (Hedenström & Alerstam 1997, Zhao et al 2017) and may explain why spring migration is faster than fall migration in many long-distance migrants (Nilsson et al 2013, Schmaljohann 2018)
Long-tailed jaegers departing the eastern Canadian Arctic traveled through Baffin Bay and Davis Strait to the North Atlantic and crossed the ocean to the western African coast (Fig. 1; Animation S1 at www.int-res.com/articles/suppl/m677p001 _supp/)

Summary

Introduction

Migratory seabirds can travel long distances across the planet, connecting distant ecosystems and exposing themselves to a diversity of environmental conditions and resources along the way. Competition for breeding territories and high reproductive success in early breeders can favor birds arriving early and in good body condition on their breeding grounds (Rowe et al 1994, Kokko 1999, Verhulst & Nilsson 2008) Under these conditions, individuals are expected to complete their spring migration as fast as possible, given constraints on flying speed and energy acquisition rate. Individuals are expected to complete their spring migration as fast as possible, given constraints on flying speed and energy acquisition rate Such a time-minimization strategy is commonly thought to play a major role during the pre-breeding migration (Hedenström & Alerstam 1997, Zhao et al 2017) and may explain why spring migration is faster than fall migration in many long-distance migrants (Nilsson et al 2013, Schmaljohann 2018). This may be especially important in species breeding at high latitudes where the summer is brief (Reséndiz-Infante & Gauthier 2020)

Methods

Results

Discussion

Conclusion