Habitat use of urban nesting yellow-legged gulls in Croatia during the breeding season

Abstract

Because of increasing urbanization, some opportunistic birds such as gulls, started to exploit various artificial marine and terrestrial food sources. To better understand urban gull ecology and habitat use, a study was done on a yellow-legged gull (Larus michahellis) during the breeding season in Zadar, a coastal city on the Adriatic Sea. Ten adult breeding yellow-legged gulls (five females and five males) were caught on building rooftops during the late incubation period and were fitted with GPS-GSM solar power transmitters. In total, 2377 trip segments (no. GPS points = 19906) were analyzed, with most of them being classified as nest attendance (56.32 %) and foraging movements (37.10 %). Tracking data showed that the gulls mostly use marine and urban areas, agricultural lands, a dump site, and grasslands. Females were more active while foraging, with a longer duration and trip segment length, travelling further away from the breeding colony, while males tended to rest more than females. Both males and females exploit various habitats for foraging and resting, however females used agricultural lands significantly more than males. Even though gulls are generalists, some individuals showed a preference for certain habitats. After calculating the proportional similarity index, individuals showed high specialization for a certain habitat.