Distribution of Olrog’s Gull Larus atlanticus from Bahía San Blas during the non-breeding period: signals of partial migration

COPELLO, SOFÍA; SUÁREZ, NICOLÁS; YORIO, PABLO; RAVASI, MARÍA T.; PAZ, JESICA A.; BORBOROGLU, PABLO GARCÍA; GRILLI, MARICEL GRAÑA; FAVERO, MARCO; SECO PON, JUAN P.

BIRD CONSERVATION INTERNATIONAL

CAMBRIDGE UNIV PRESS

Año: 2020 p. 1 - 10

0959-2709

The Olrog?s GullLarus atlanticus is an endemic and threatened species of the south-western Atlantic.Little is known about its movements during the non-breeding period. Theobjective of this study was to analyse the migration of the species by trackingadults from Bahıa San Blas (Buenos Aires province, Argentina) with geolocatorsand using information of sightings of ringed gulls. Differences between malesand females were evaluated using tracking data and ringed data were used todetermine age differences. A single core area (kernel 50%) from 21 trackedbirds was identified. This area included the study colony and also otherbreeding colonies located up to 300 km to the north. The range area (kernel95%) included coastal areas up to 1,000 km from the colony. All sightings ofringed gulls (n = 41) occurred north of the breeding colony, however 12 adultindividuals were sighted during the winter in its breeding grounds. Our resultssuggest the occurrence of partial migration behavior in Olrog?s Gull. Themigration pattern reported here implies than during the non-breeding season,breeding and wintering areas away from the nesting grounds should be consideredas one system in the design of conservation strategies for this regionallythreatened gull.