Resumen de Influencia de las temperaturas mínimas en un grupo invernante de Gaviota Sombría Larus fuscus y Gaviota Reidora Larus ridibundus en el río Guadiana (sudoeste de España)
The influence of minimum temperatures on a wintering group of Lesser Black-backed Gulls Larus fuscus and Black-headed Gulls Larus ridibundus on the River Guadiana (south-west Spain) Analysis is presented of the influence of minimum temperatures on the number of wintering Lesser Black-backed Gulls Larus fuscus and Black-headed Gulls Larus ridibundus and on the proportion of adults in the groups observed at a resting area located on the River Guadiana (south-west Spain). A significant negative correlation was found between the minimum temperatures and the number of individuals of the two species, as well as between the minimum temperatures and both age classes (adult and subadults) of Blackheaded Gulls; in contrast, only subadult, not adult, Lesser Blackbacked Gulls were affected by this variable. The increase in the number of gulls in the resting area could be related to the increase in the physiological cost of keeping warm and to the decrease of resources when the temperatures drop.
