Trophic ecology, habitat use and ecophysiology of Audouin’s Gull (Larus audouinii) in the Ebro Delta

• Autores: Manuel García Tarrasón
• Directores de la Tesis: Carola Sanpera Trigueros (dir. tes.), Lluis Jover Armengol (dir. tes.)
• Lectura: En la Universitat de Barcelona ( España ) en 2014
• Idioma: inglés
• Tribunal Calificador de la Tesis: Javier María Ferrer Parareda (presid.), Daniel Oro de Ribas (secret.), Mauro Fasola (voc.)
• Materias:
  • Ciencias de la vida
    • Biología animal (zoología)
      • Ecología animal
      • Fisiología animal
      • Ornitología
      • Vertebrados
• Enlaces
  • Tesis en acceso abierto en:  TDX  Dipòsit Digital de la UB 
• Resumen

  • The results presented in this thesis have shown the strong dependence of Audouin’s gull from the Ebro Delta on fisheries. Foraging movements of breeding birds showed a great association with fishing activities (specially trawling), determining the most of its at-sea distribution on work days. An increase in the use of rice field habitats was also detected in absence of fishing activities (during weekends) due to the opportunistic feeding on the American crayfish. However, a key aspect presented in this thesis was the significant sex-differences in their foraging behaviour in relation to fisheries. Female Audouin’s gull tended to perform longer at-sea foraging trips on weekends compared to males, probably due to the need of feeding on high quality resources after laying instead of the easily available but lower quality American crayfish. This great dependence on fishing activities was also reflected in the resource allocation into the clutch. An isotopic ?15N enrichment in the albumen of eggs synthesized during the weekends was observed, which is attributed to an increase in the consumption of rice field resources as well as to the mobilization of female reserves. However, rice field diets were associated to lower antioxidant capacity in the eggs. Also, rice field diets were related to smaller egg size. Finally, the limiting nature of calcium (in constraining egg synthesis) and antioxidant molecules (decreasing their concentration especially in the latter eggs of the clutch) were also revealed for females.