Does intraspecific competition facilitate age separation in timing of southward migration in waders? |
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| Institution: | 1. Department of Teacher Training and Biodiversity Studies, University of Łódź, Banacha 1/3, 90-237 Łódź, Poland;2. Medical University of Łódź, Sterlinga 1/3, 91-425 Łódź, Poland;1. Departamento de Biología Vegetal y Ecología, Facultad de Biología, Universidad de Sevilla, Apartado 1095, E-41080 Sevilla, Spain;2. Laboratorio de Ecología de Pastizales, Av Angel Gallardo 470, 2° piso Área de Botánica, Buenos Aires, Argentina;3. Department of Plant Ecology, University of Bayreuth, Universitätsstrasse 30, 95440 Bayreuth, Germany;1. Department of Botany and Zoology, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic;2. Institute of Botany, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 23 Bratislava, Slovakia;3. Department of Plant Ecology and Environmental Conservation, Faculty of Biology, Biological and Chemical Research Centre, University of Warsaw, ul. Żwirki i Wigury 101, PL-02-096 Warsaw, Poland;1. Naiman Desertification Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China;2. Extreme Stress Resistance and Biotechnology Laboratory, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu 730000, China;1. Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa;2. Invasive Species Programme, South African National Biodiversity Institute, Kirstenbosch Research Centre, Claremont 7735, South Africa |
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| Abstract: | In many Palaearctic wader species there is a clear separation in the timing of adult and juvenile southward migration. This phenomenon is traditionally explained by the selection on adults to depart early from breeding grounds and necessity of juveniles to prepare longer for migration. In this study we hypothesize that late departure from natal grounds may also be adaptive for juveniles, as it allows them to avoid intensified interference competition at stopover sites with adult, usually more dominant conspecifics. To test this hypothesis we analysed long-term data on stopover behaviour of juvenile wood sandpipers (Tringa glareola) staying at a central Polish stopover site under varying levels of competition from adult birds. The results clearly indicated that juveniles were highly disadvantaged by the simultaneous presence of adults at the same staging site, as under intense competition from older conspecifics they refuelled more slowly and attained lower fat reserves. It was also found that juveniles which were forced to compete with adults left the site quickly and possibly searched for more favourable staging places. All these imply that delayed departure from natal grounds may be adaptive for juvenile waders, allowing them to mismatch the timing of their first migration with the peak of adult passage and, thus, reduce the negative consequences of intraspecific competition during migration. |
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| Keywords: | Competition Timing of migration Waders Wood sandpiper |
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