Land or sea? Foraging area choice during breeding by an omnivorous gull
Research output: Contribution to journal › Article
Generalist predators may vary their diet and use of habitat according to both internal state (e.g. breeding stage) and external (e.g. weather) factors. Lesser black-backed gulls Larus fuscus (Linnaeus 1758) are dietary generalists, foraging in both terrestrial and marine habitats during breeding. We investigate what affects the gulls’ propensity to forage at sea or on land. We assess the importance of terrestrial foraging to gulls in the Baltic Sea (sub. sp. L. f. fuscus), looking especially at their use of agricultural fields.
Through the GPS tracking of 19 individuals across 3 years we tracked 1038 foraging trips and found that 21.2 % of foraging trips were predominantly terrestrial, 9.0 % were a mix of terrestrial and marine, and 68.5 % were exclusively marine. Terrestrial trips were (1) more frequent when departing around sunrise, whereas marine trips occurred throughout the day. Additionally, trips with mostly land-based foraging decreased as the breeding season progressed, suggesting dietary switching coincident with the onset of chick provisioning. (2) During cloudy and cold conditions terrestrial foraging trips were more likely. (3) We found no differences between sexes in their land-based foraging strategy. (4) Gull individuals showed great variation in foraging strategy. Using observations of agricultural fields, carried out for one year, we found that (5) gulls preferentially foraged on fields with short vegetation, and there was a positive association with occurrence of waders and other species of gulls. (6) The availability and use of these preferred fields decreased through the breeding period.
This study found high prevalence of terrestrial foraging during early breeding as well as support for dietary switching early in the breeding season. The overall tendency for marine or terrestrial foraging was consistent within individuals, with gull identity accounting for much of the variation observed in foraging trips. Our results suggest that anthropogenic terrestrial food sources may play a role in the low breeding success of these gulls through either variation in quantity and/or quality. Finally, our study demonstrates the potential of combining data from GPS-tracking of individual animals with the ‘ground-truthing’ of habitat visited to elucidate the otherwise nebulous behavior of a generalist predator.
|Research areas and keywords||
Subject classification (UKÄ) – MANDATORY
|Number of pages||14|
|Publication status||Published - 2016 May 15|
Related research output
Research output: Thesis › Doctoral Thesis (compilation)
Niklas Larsson, Atticus Pinzon-Rodriguez, Arne Hegemann, Brianne Addison, Charlie Cornwallis, Giuseppe Bianco, INGRID SASSENHAGEN, Jerker Vinterstare, Julian Melgar, Júlio Manuel Neto, Lasse Jakobsen, Mikael Ekvall, Mihaela Ilieva, Natalia Annenkova, Pallavi Chauhan, Sylvie Tesson, Yannis Vardanis, Catherine Tayleur, Emily Baird, Olle Lind, Jakob Löndahl, Tina Santl-Temkiv, Anders Hedenström, Åke Lindström, Anders Nilsson, Bengt Hansson, Dennis Hasselquist, Erik Svensson, Henrik Smith, Helena Westerdahl, Jan-Åke Nilsson, Johan Bäckman, Katarina Hedlund, Lars Råberg, Maria Ingimarsdottir, Martin Green, Maria Sandell, Martin Stjernman, Nils Kjellén, Ola Olsson, Rachel Muheim, Richard Ottvall, Staffan Bensch, Xiuhong Yang, Sara Snogerup-Linse, Heiner Linke, Mikkel Brydegaard Sorensen, Patrik Lundin, Sune Svanberg, Zuguang Guan, Ann-Sofie Albrekt, Anders Hargeby, Anders Persson, Christer Brönmark, Emma Kritzberg, Karin Rengefors, Lars-Anders Hansson, Olof Berglund, Wilhelm Granéli, Alice Nicolle, Ben Chapman, Christian Skov, Johan Ahlgren, Jakob Brodersen, Jessica von Einem, Kaj Hulthén, Kelly Gutseit, Karen Lebret, Lynn Ranåker, MATTIAS EKVALL, Mercy Lard, MIKAEL JÖNSSON, PER HALLGREN, Peter Ljungberg, Samuel Hylander, Tony Fagerberg, Therese Jephson, Tomas Johansson, Bjorn Canback, Bengt Danielsson, Christoffer Johansson, Emma Ådahl, Florian Muijres, Jörgen Ripa, Melissa Bowlin, Niclas Jonzén, Per Henningsson, Roger Härdling, Andreas Nord, Arzu Gursoy, Asghar Muhammad, Anna Nilsson, Anna Runemark, Barbara Tschirren, Cecilia Nilsson, Håkan Karlsson, Irene Pala, Juliana Dänhardt, Johan Nilsson, Jens Rydell, Jonas Waldenström, Keith Larson, Kristina Karlsson, Kristin Scherman, Mikael Åkesson, Martin Andersson, Maja Tarka, Maren Wellenreuther, Max Lundberg, Miriam Liedvogel, Maj Rundlöf, Martin Wintersparv Stervander, Machteld Verzijden, Olof Hellgren, Raymond Klaassen, Roine Strandberg, Susanne Åkesson, SANDRA SKÖLD CHIRIAC, Sophia Engel, Sissel Sjöberg, Sara Naurin, Thomas Alerstam, Tom J Evans, Torbjörn von Schantz, Ulf Ottosson, Marie Dacke & Helena Osvath
2008/06/01 → 2018/12/31
Project: Research › Interdisciplinary research