Coastal bird community change following an increase of pinnipeds at a site in northern Argentina: A 14-year study

Abstract

We report here changes in bird assemblages over a 14-year interval at the Port of Mar del Plata, Argentina, and the adjacent beach before (PRE) and after (POST) South American Sea Lions Otaria flavescens increased at a local haul-out. Abundance and number of bird species were compared between periods, between sites (beach, sea lion rookery, and port sheds), and between breeding and non-breeding seasons of the birds’ annual cycle. A total of 13 116 birds belonging to 15 species were recorded. Total bird abundance was higher during the POST period compared to the PRE period, regardless of the season. Larids occurred in all sampled areas but with higher abundance at Punta Mogotes beach. The Kelp Gull Larus dominicanus, Brown-hooded and Grey-headed gulls Chroicocephalus spp., and the Snowy Sheathbill Chionis albus dominated assemblages during the PRE sea lion increase period, while Kelp Gulls, Brown-hooded Gulls, and the South American Tern Sterna hirundinacea dominated the POST period. Variation in the numbers of birds may be related to changes in feeding opportunity related to increased human activity (e.g., fishery wastes) as well as expansion of the local rookery of South American Sea Lions, another food source.