title: Modelling terrestrial and marine foraging habitats in breeding Audouin's gulls Larus audouinii: timing matters.
abstract: Although the breeding ecology of Audouin's gull has been widely studied, its spatial distribution patterns have received little attention. We assessed the foraging movements of 36 GPS-tracked adult Audouin's gulls breeding at the Ebro Delta (NW Mediterranean), coinciding with the incubation period (May 2011). This also coincided with a trawling moratorium northwards from the colony. We modelled the distribution of the gulls by combining these tracking data with environmental variables (including fishing activities from Vessel Monitoring System, VMS), using Maxent. The modelling range included both marine and terrestrial areas. Models were produced separately for every 2h time interval across the day, and for 2 fishing activity scenarios (workdays vs. weekends), allowing to assess the spatio-temporal distribution patterns of the gulls and the degree of association with fisheries. During workdays, gull distribution at sea fully matched with fishing activities, both trawling (daylight) and purse-seining (nightime). Gulls tended to avoid the area under trawling moratorium, confirming the high influence of fisheries on the distribution patterns of this species. On weekends, gulls made lesser use of the sea and tended to increase the use of rice fields. Overall, Audouin's gull activity was more intense during dailight hours, although birds also showed nocturnal activity, on both workdays and weekends. Nocturnal patterns at sea were more disperse during the latter, probably because these gulls are able to capture small pelagic fish at night in natural conditions, but tend to congregate around purse-seiners (which would enhance their foraging efficiency) in workdays. These results provide important insight for the management of this species. This is of particular relevance under the current scenario of European fisheries policies, since new regulations are aimed at eliminating discards, and this would likely influence Audouin's gull populations.
authors: Programa marino, Delegació de Catalunya, SEO/BirdLife, Barcelona, Spain.
authors: Juan
authors: J
authors: Bécares
authors: Departament de Biologia Animal, Universitat de Barcelona, Barcelona, Spain.
authors: Manuel
authors: M
authors: García-Tarrasón
authors: Grup d'Ecologia del Paisatge, Àrea de Biodiversitat, Centre Tecnològic Forestal de Catalunya, Solsona, Spain.
authors: Dani
authors: D
authors: Villero
authors: Departament de Biologia Animal, Universitat de Barcelona, Barcelona, Spain.
authors: Santiago
authors: S
authors: Bateman
authors: Departament de Salut Pública, Facultat de Medicina, Universitat de Barcelona, Barcelona, Spain; IRBio-Research Institute of Biodiversity, University of Barcelona, Barcelona, Spain.
authors: Lluís
authors: L
authors: Jover
authors: Dirección General del Medio Natural y Política Forestal, MAGRAMA, Madrid, Spain.
authors: Víctor
authors: V
authors: García-Matarranz
authors: Departament de Biologia Animal, Universitat de Barcelona, Barcelona, Spain; IRBio-Research Institute of Biodiversity, University of Barcelona, Barcelona, Spain.
authors: Carolina
authors: C
authors: Sanpera
authors: Programa marino, Delegació de Catalunya, SEO/BirdLife, Barcelona, Spain.
authors: José Manuel
authors: JM
authors: Arcos
mesh_terms: D000818:Animals; D046091:Charadriiformes / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D005398:Fisheries; D005399:Fishes; D005523:Food Supply; D040362:Geographic Information Systems / Q000295:instrumentation; D006802:Human Activities; D008297:Male; D008522:Mediterranean Sea; D008954:Models, Biological; D011235:Predatory Behavior / Q000502:physiology*; D057233:Radio Frequency Identification Device; D012621:Seasons; D012726:Sexual Behavior, Animal; D013030:Spain; D013997:Time Factors; D014866:Waste Products
chemical_list: D014866:Waste Products