Species-specific population trends detected for penguins, gulls and cormorants over 20 years in sub-Antarctic Fuegian Archipelago

RAYA REY A; N ROSCIANO; M LILJESTHRÖM; R SAENZ SAMANIEGO; A SCHIAVINI

POLAR BIOLOGY

SPRINGER

Lugar: Berlin; Año: 2014 vol. 37 p. 1343 - 1360

0722-4060

Understanding the dynamics and causes ofpopulation trends are essential for seabird conservation.Long-term studies of seabirds at high-latitude (Antarctic,sub-Antarctic and Arctic) regions have shown contrastingspecies-specific trends in population size in response toclimate change and anthropogenic pressures. We havestudied for the last 20 years (1992?2012) the populationtrends of seven seabird species that breed in the BeagleChannel, south-eastern Tierra del Fuego and at StatenIsland, a sub-Antarctic region in southern Argentina. Thenumbers of Magellanic and Gentoo Penguins increasedsignificantly since 1992 (by[15 % year-1). In comparison,the populations of Imperial Cormorants, Dolphin Gulls andKelp Gulls increased at slower rates ( % year-1), whilethe Rock Cormorant population even decreased by 1.3 %year-1. At Staten Island, the numbers of RockhopperPenguins decreased by 24 % between the censuses of 1998and 2010, whereas the population of Magellanic Penguinsincreased by 227 % during the same period. Over the studyperiod, air and sea-surface temperatures remained stable inour study area, suggesting that the detected populationchanges are not driven by the climate. This finding contrastswith the detected links between increasing temperaturetrends and seabird population changes reported fromAntarctic and Arctic regions. The level of tourism and sizeof the permanent human population has increased in theBeagle Channel area during the last 20 years and could beresponsible for the increase of gull populations. The seabirdspecies that received the highest number of visitors(Imperial Cormorants and penguin species) seem to beadapted or at least indifferent to pressures exerted bytourism, as their populations increased during the studyperiod. In addition, increasing numbers of seabirds in thearea may generally be leading to higher abundances ofscavenging species (e.g. gulls).