Short distance migrants travel as far as long distance migrants in lesser black‐backed gulls Larus fuscus

Abstract

Migration strategies differ greatly among and within avian populations. The associated trade‐offs and fitness consequences of diverse strategies and how they persist are pertinent questions in migration research. Migration is a costly endeavour, presumably compensated for by better survival conditions in the non‐breeding area. One way to assess the cost of alternative strategies is to investigate the investment in movement across the entire annual cycle, an assessment made increasingly feasible with improvements in tracking technology. Our study focuses on lesser black‐backed gulls, generalist seabirds that exploit a broad range of resources, exhibit diverse migration strategies and have potentially altered migration strategies in response to human activities and climate change. We used GPS tracking to quantify lesser black‐backed gulls’ movement throughout their annual cycle and compare trade‐offs among four migration strategies. The annual cumulative distance travelled by long distance migrants wintering in west Africa, over 4000 km from their breeding colony, did not differ significantly from individuals of the same breeding colony wintering only a few hundred kilometres away in Great Britain. Short distance migrants returned to the colony first, and long distance migrants returned last. Sex and wing length were not correlated with maximum range, cumulative distance travelled or timing. Individuals spent only a small proportion of their time in flight and spent on average 17% of their time at sea throughout an annual cycle, suggesting a reliance on inland resources for many individuals. Analysing movement throughout the annual cycle can change our perspective and understanding of consequences of different migration strategies. Our study shows that a range of migration strategies coexists and we propose that the long term costs and benefits of these strategies balance out. Diversity in migration strategies may contribute to the resilience of this species in the face of ongoing anthropogenic impact on the environment.

Crayfish invasion facilitates dispersal of plants and invertebrates by gulls

“…Larus fuscus has an increasing population of around 600,000 birds in western Europe and west Africa (Wetlands International, ). Therefore, given their regular movements within and beyond southern Spain (Bouten et al., ; Shamoun‐Baranes, Burant, Loon, Bouten, & Camphuysen, ), L. fuscus may facilitate LDD of plants and invertebrates, enabling their rapid spread over broad areas. Tracking of individual gulls shows they move between Doñana ricefields and other Andalusian wetlands including Doñana fish ponds and natural closed‐basin lakes such as Fuente de Piedra in Malaga (see Bouten et al., ).…”

“…Other waterbirds feeding on crayfish in ricefields (Tablado et al., ) are likely to disperse these plant species, and a recent review of dabbling duck diet recorded four of the 11 species (Soons et al., ). Moreover, the migration routes of L. fuscus and other waterbirds feeding on crayfish in Spain (e.g., white stork Ciconia ciconia ) extend into Africa (Rotics et al., ; Shamoun‐Baranes et al., ). Accordingly, there is a potential for LDD of plants and invertebrates between continents.…”

Early arrival at breeding grounds: Causes, costs and a trade‐off with overwintering latitude

“…More broadly, bird migration is a flexible phenomenon (Alerstam, Hedenström, & Åkesson, ; Newton, ), and many species display significant variation in migration flyways between and within populations (e.g. Barbraud, Barbraud, & Barbraud, ; Shamoun‐Baranes, Burant, Loon, Bouten, & Camphuysen, ; Weimerskirch et al., ). Further research on the differences and trade‐offs between migration strategies would advance our knowledge on the evolution and conservation of bird migration.…”

Sample size required to characterize area use of tracked seabirds

“…All handling of birds was in accordance with ethical protocols set out by the British Trust for Ornithology (BTO; Redfern and Clark ), responsible for licensing of bird ringing activities in the United Kingdom. Further licensing endorsements under individual ringing permits were approved by the Special Methods Technical Panel, an independent body reporting to the BTO Ringing Committee, and followed strict guidelines in compliance with the panel and established procedures previously used on this species (Shamoun‐Baranes et al , ). Of the 25 tags deployed, 24 produced data; 1 bird lost its tag immediately after deployment (Thaxter et al ).…”