The status of the European Shag Phalacrocorax aristotelis population on the Atlantic coast of the Iberian peninsula

Velando, A., Docampo, F. & Alvarez, D. The status of the European Shag Phalacrocorax aristotelis population on the Atlantic coast of the Iberian peninsula. Atlantic Seabirds (1999).


A regional analysis of the status of the European Shag Phalacrocorax aristotelis population on the Atlantic coasts of the Iberian Peninsula is presented. This is the first census to be made of this population. The total population was estimated to be approximately 2239 pairs in 1990-94. The first counts from Euskadi and Cantabria are presented, indicating a population of 57-67 pairs in Euskadi in 1994 and 36-41 pairs in Cantabria in 1992. The first census in Asturias dates from 1986 with 98-124 pairs, and the population has increased at an annual rate of 6%, reaching 199-250 pairs in 1997. There are records of partial counts made in Galicia since 1976. The population appears to have stabilised on the Cíes and Ons Islands (Rías Baixas, Pontevedra), where it was increasing at 8-9% annually. The total count of 1462 breeding pairs on Cíes and Ons accounts for 66% of the Atlantic Iberian population. As far as is known, the population in Portugal has stabilised, but there has been no census of the southern colonies since 1983. On the island of Berlenga there were 60 pairs in 1990-94, the number of pairs having changed very little since the first count in 1939.

Climate Influences Fledgling Sex Ratio and Sex-Specific Dispersal in a Seabird

Barros, Á., Álvarez, D. & Velando, A. Climate Influences Fledgling Sex Ratio and Sex-Specific Dispersal in a Seabird. PLoS ONE 8, e71358 (2013).8): e71358. doi:10.1371/journal.pone.0071358

Climate influences the dynamics of natural populations by direct effects over habitat quality but also modulating the phenotypic responses of organisms’ life-history traits. These responses may be different in males and females, particularly in dimorphic species, due to sex-specific requirements or constraints. Here, in a coastal seabird, the European shag (Phalacrocorax aristotelis), we studied the influence of climate (North Atlantic Oscillation, NAO; Sea Surface Temperature, SST) on two sex-related population parameters: fledgling sex ratio and sex-specific dispersal. We found that fledgling sex ratio was female skewed in NAO-positive years and male skewed in NAO-negative years. Accordingly, females dispersed a longer distance in NAO-positive years when females were overproduced, and on the contrary, males dispersed more in NAO-negative years. Overall, our findings provide rare evidence on vertebrates with genetic sex determination that climate conditions may govern population dynamics by affecting sex-specific density and dispersal.