A gull that scarcely ventures on the ocean: Yellow-legged Gulls Larus michahellis atlantis on the oceanic island of Madeira

Doi: https://doi.org/10.13157/arla.66.1.2019.sc4

Authors: Joana ROMERO, Paulo CATRY, Dília MENEZES, Nádia COELHO, João PAULO SILVA, José Pedro GRANADEIRO

E-mail: j-romero@live.com

Published: Volume 66.1, January 2019. Pages 101-112.

Language: English

Keywords: fishing activity, GPS tracking, habitat-use, human waste and stable isotopes

Summary:

The Yellow-legged Gull Larus michahellis atlantis (YLG) is a generalist and opportunistic species that explores different habitats and resources and easily adapts to humanised environments, sometimes posing problems related to aircraft security, public health or predation on other species, for example. We examined the distribution and foraging behaviour of YLGs on the oceanic island of Madeira. GPS-GSM devices were deployed on ten breeding individuals and samples of blood (adults) and feathers (chicks) were collected to examine their stable isotope signatures in relation to those of their prey. Tracked YLGs did not migrate. Birds remained mostly inland during the day (up to 60% of fixes) and barely 5% of the fixes were at sea. Eighty-eight out of 192 gull trips to the sea were in interaction with local fishing vessels, 91% of which involving purse seiners that were active at night. The diet of the adult YLGs consisted of refuse, fish and small petrels, whereas the chick diet included mainly fish. YLGs on this oceanic island are strongly dependent on anthropogenic resources, scarcely relying on natural marine prey. The desired control of this gull population could perhaps be achieved by the reduction of accessibility to organic waste.

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