20th century Animals Anthropocene Anthropogenics Conservation Dietary assessments Ecology Food supply Human activities Invertebrata Isotopes Land fill Lari michahellis Larus michahellis Longitudinal studies Longitudinal study Marine biology Natural resources Stable isotope analysis Stable-isotope analysis Terrestrial invertebrate Trophic plasticity Yellow-legged gull Yellow-legged gulls central place foraging conservation management conservation status feeding behavior food supply foraging behavior