Colonia reproductiva de la gaviota cáhuil (Chroicocephalus maculippenis) y de capucho gris (C. cirrocephalus) en una laguna urbano-costera con alto impacto antrópico en Mar del Plata, Argentina

Abstract

We report findings regarding nesting, nestlings and fledglings of a breeding colony of Brown-hooded gulls (Chroicocephalus maculipennis) and of Gray-hooded gulls (C. cirrocephalus) in an urban-coastal lagoon with high human impact in Mar del Plata, Argentina. We observed periodically both colonies from September 2022 to January 2023. In September, individuals of both species flew and perched on vegetation islets in a lagoon of Punta Mogotes, initiating colony formation. In the middle of October, each species had initiated nesting on separate islets. In early December, we recorded 37 nests of Brown-hooded gulls and five of Gray-hooded gulls. In the third week of December, six nests with nestlings and eight fledglings were within the Brown-hooded Gull colony. We did not record nestlings and fledglings in the Gray-hooded Gull colony. In late December, no gull pair was nesting. During the fourth week of December, a White-faced Ibis (Plegadis chihi) flock was nesting on the islets, where Brown-hooded gulls nested. We observed 16 breeding individuals and 26 occupied nests. In early January, it had only nine adult White-faced Ibis and six occupied nests. Future studies should evaluate how the diverse local human perturbations affect the breeding success of these small urban gull colonies.