Abstract
Research focused on evaluating how human food subsidies influence the foraging ecology of scavenger species is scarce but essential for elucidating their role in shaping behavioral patterns, population dynamics, and potential impacts on ecosystems. We evaluate the potential role of humans in shaping the year‐round distribution and habitat use of individuals from a typical scavenger species, the yellow‐legged gull (Larus michahellis), breeding at southwestern Spain. To do this, we combined long‐term, nearly continuous GPS‐tracking data with spatially explicit information on habitat types and distribution of human facilities, as proxied by satellite imagery of artificial night lights. Overall, individuals were mainly associated with freshwater habitats (mean proportion, 95% CI: 40.6%, 36.9%–44.4%) followed by the marine‐related systems (40.3, 37.7%–42.8%), human‐related habitats (13.5%, 13.2%–13.8%), and terrestrial systems (5.5%, 4.6%–6.5%). However, these relative contributions to the overall habitat usage largely changed throughout the annual cycle as a likely response to ecological/physiological constraints imposed by varying energy budgets and environmental constraints resulting from fluctuations in the availability of food resources. Moreover, the tight overlap between the year‐round spatial distribution of gulls and that of human facilities suggested that the different resources individuals relied on were likely of anthropogenic origin. We therefore provide evidence supporting the high dependence of this species on human‐related food resources throughout the annual cycle. Owing to the ability of individuals to disperse and reach transboundary areas of Spain, Portugal, or Morocco, international joint efforts aimed at restricting the availability of human food resources would be required to manage this overabundant species and the associated consequences for biodiversity conservation (e.g., competitive exclusion of co‐occurring species) and human interests (e.g., airports or disease transmission).
Highlights
Over millennia, humans have altered ecosystems through habitat destruction, pollution, species extinctions, and biological invasions, these impacts have been exacerbated recently during the Anthropocene (McCauley et al, 2015; Rockström et al, 2009; Steffen et al, 2011)
The efficient exploitation of anthropogenic food subsides has directly contributed to the expansive dynamics of scavenger populations all over the globe (Newsome et al, 2015)
Our understanding on the behavioral patterns of scavenger species, their population dynamics and their potential impacts on highly anthropogenic landscapes necessarily pass through a proper comprehension on their degree of dependence on human food subsides (Oro et al, 2013)
Summary
Humans have altered ecosystems through habitat destruction, pollution, species extinctions, and biological invasions, these impacts have been exacerbated recently during the Anthropocene (McCauley et al, 2015; Rockström et al, 2009; Steffen et al, 2011). We evaluated how human activities in a widely transformed and heterogeneous landscape can shape the foraging ecology of a typical scavenger species in both space and time Besides their ecological interest within the current context of human impacts on ecosystems' structure and functioning (Oro et al, 2013), these results may have important management implications, such as providing information about those habitats, and food subsidies, that may contribute the most to the expansive dynamics of this species (Martínez-Abraín & Jiménez, 2016; Payo-Payo et al, 2015; Vidal, Medail, & Tatoni, 1998)
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