Browsing by Author "Bocelli, Giulia"
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- Anthropogenic disturbance effects on two sympatric species of gulls, Larus michahellis & Ichthyaetus audouinii, during the breeding season in Deserta island (Portugal)Publication . Bocelli, Giulia; Norte, Ana Cláudia; Serrão, EsterThe presence of humans and their activities are intensifying in coastal ecosystems leading to disturbance of wildlife and strong habitat modifications. Colonial seabirds that breed in coastal areas are an example of a particularly susceptible group to such pressures. Among the methods to assess the anthropogenic impact, physiological records can account for stress responses behind possible behavioral adaptations. We investigated if and how the anthropogenic presence in the reproductive colonies of the two sympatric species of seagulls, impact on their physiology and behavioral response. We selected the Yellow-legged gull (Larus michahellis) and the Audouin’s gull (Ichthyaetus audouinii), due to their differential habits of interaction with humans. We recorded their heart rate during a designed walking-operator’s disturbance experiment for a total of 6 days during incubation. With this aim we deployed artificial egg devices equipped with a microphone and a thermometer in 24 nests of each species, in two selected areas of each reproducing colony. We characterized each experimental nest by deploying a thermohygrometer to track the microhabitat temperature, recording vegetation maximum high and percentage cover, and using the dummy egg thermometer for nest chamber temperatures evaluation. Both species suffered an increase in heart rate just before leaving the nest unattended when disturbed by the operator. Contrary to expectation, the variation in heart rate response from undisturbed to disturbed conditions was similar between species. External factors such as the environmental temperature and the vegetation coverage proved to be related for both species, with the heart rate response, time necessary to resume incubation, and the hatching success. This study represents a first insight into the stress physiology of Yellow-legged and the Audouin’s gulls and confirms the utility of the artificial egg as a minimal-invasive biologging tool for physiological research in incubating birds. These results lead us to hypothesize that global warming, extension of the human niche, and landscape modification, may threaten the reproductive success and fitness of colonial seabirds.