engleski

WHAT IS BOTHERING AUDOUIN'S GULL IN CROATIA – PRELIMINARY RESULTS OF BREEDING COLONIES SURVEILLANCE WITH CAMERA TRAPS

The Audouin’s Gull Larus audouinii (AG) breeds on small, uninhabited off-shore islands in Croatian part of the Adriatic Sea. Croatian breeding population is estimated at 60-70 pairs. Black Rat Rattus rattus and Yellow-legged Gull Larus michahellis (YLG) are known predators on AG eggs, chicks and adults and can affect its breeding success. Livestock can cause trampling and disturbance. Eight camera traps were set up in AG colonies on two uninhabited islands of Lastovo archipelago in the southern Adriatic Sea in order to examine the impact of predation and disturbance on AG. Camera traps were mounted in front of the nest containing eggs during the incubation period. Due to several malfunctions, period when camera traps were active vary between 17 and 44 days. YLG was the predator with the highest sighting rate. Egg predation by rats and chick predation by YLG were recorded. Goats commonly caused ground intrusions, but with no evident damage. Due to high mobility of AG chicks and difference among shooting angles of camera traps, breeding success was not recorded. Chicks ringing resulted with only 0.13 and 0.69 fledged chicks per nest in colonies 1 and 2 respectively. While colony 2 breeding success (9 chicks from 13 breeding pairs) was in accordance with the literature, on colony 1 it was much lower (4 chicks from 29 breeding pairs). Only 5 nests at the colony 2 were monitored and it was not possible to identify the reason for such low breeding success. Presence and evident predating behaviour of both rats and YLG affected breeding success of AG. We recommend the maintenance of deploying camera traps in AG colony surveillance as a good tool for monitoring of predation pressure, urge on projects for finding solutions for mitigation of YLG pressures on AG population and starting rat eradication program on islets that hold AG breeding colonies.

Lariidae, Adriatic Sea, invasive species

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