Population trends and reproductive success at a frequently visited penguin colony on the western Antarctic Peninsula

Petermann Island (65A degrees 10'S, 64A degrees 10'W), one of the Antarctic Peninsula's most frequently visited locations, is at the epicenter of a rapid shift in which an Ad,lie penguin dominated fauna is becoming gentoo penguin dominated. Over the course of five seasons, the breeding productivity of Ad,lie and gentoo penguins breeding at Petermann Island were monitored to identify drivers of this rapid community change. The impact of tourist visitation on breeding success was also investigated. Consistent with larger trends in this region, the Ad,lie penguin population decreased by 29% and the gentoo penguin population increased by 27% between the 2003/2004 and 2007/2008 seasons. Reproductive success among Ad,lie penguins ranged from 1.09 to 1.32 crSched chicks/nest, which was higher than or comparable to other sites and is an unlikely explanation for the precipitous decline of Ad,lie penguins at Petermann Island. Whereas gentoo penguin reproductive success was lowest in colonies frequently visited by tourists, Ad,lie penguin colonies frequently visited by tourists had higher reproductive success than those visited only occasionally. These results are placed in the context of other studies on reproductive success and the impact of tourist visitation on breeding colonies of Ad,lie and gentoo penguins.