Population trends of Imperial Cormorants (Leucocarbo atriceps) in northern coastal Argentine Patagonia over 26 years

Monitoring programmes are essential for detecting population changes, but data series are difficult to sustain over time. Additionally, wide-scale monitoring is needed to adequately interpret demographic behaviour given the metapopulation dynamics characteristics ofmost seabird species and to understand the underlying factors, such as anthropogenic pressures and climate change. Many cormorant species are largely dependent on coastal marine environments, which are subject to increasing pressures from human activities. Here, we update information on the distribution and size of Imperial Cormorant (Leucocarbo atriceps) colonies along 1,000 km of coastline in Argentina, and review published information to assess population trends at different spatial scales over 26 years (1990-2016). During 2016, the number of nests per colony ranged between 2 and 5,617 (median: 441 nests; n = 26). Total number of breeding pairs was estimated at 21,482. During the study period, two new locations were colonised, whilst another two were abandoned. Significant growth rates ranged from 1.022 to 1.117 (median: 1.036; n = 6) for increasing colonies and from 0.580 to 0.977 (median: 0.962; n = 8) for declining colonies, but the overall breeding population remained stable between 1990 and 2016 (λ = 1.000, C.I. 95% = 0.991-1.008). Our study provides one of the longest time series on seabird breeding numbers along a wide coastal sector in South America. Given the high yearly variability in nest numbers at individual Imperial Cormorant colonies, as well as the observed establishment and extinction of colonies, large scale and long term monitoring is necessary for a comprehensive understanding of overall changes in the population distribution patterns.

Fil: Yorio, Pablo Martin. Wildlife Conservation Society Argentina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina

Fil: Pozzi, Luciana Melina. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina

Fil: Herrera, Gonzalo. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina

Fil: Punta, Gabriel. Universidad Nacional de la Patagonia "San Juan Bosco"; Argentina. Secretaría de Pesca de la Provincia del Chubut; Argentina

Fil: Svagelj, Walter Sergio. Universidad Nacional de Mar del Plata; Argentina

Fil: Quintana, Flavio Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Biología de Organismos Marinos; Argentina