PARENT SESSION
Monday, August 7, 8:00-11:30 am
COS 13 - Avian ecology
Heritage Ballroom I, Marriott
Presiders: J Martin and B Reynolds

The influence of climate variation on Magellanic penguins.

Boersma, Dee^*,1, Rebstock, Ginger¹, ¹ University of Washington, Seattle, WA

ABSTRACT- Punta Tombo, Argentina has the largest colony of Magellanic penguins in the world. For the last 22 years we have followed the breeding cycle of these birds, weighing adults, measuring eggs, and determining their reproductive success. The nesting density has declined by an order of magnitude in some areas of the colony since the early 1980s. Census data of the same points from 1987 to 2005 showed active nests declined rapidly reaching a low in 1991 after an oil spill and is now stabilized at about a 20% decline. The changes in the population are in part due to reduced survival and recruitment of juveniles since the mid 1980s. Changes in reproductive success of the colony may have little impact on the breeding population as survival and recruitment of fledglings appears to be highly variable among years. In general, when breeding penguins arrived later they were in poorer body condition, eggs were smaller, and reproductive success lower. Yearly satellite-tracking data of breeding penguins over the last decade showed that male penguins were swimming on average about 110 km farther on their first incubation trip, although variation among years was high. Late arrival and longer foraging trips may be a result of penguins having to go farther north early in the season to find food. Climate variation appears to be causing a decline of the largest colony and establishment and growth of new colonies farther north. Changes in the distribution and abundance of Magellanic penguins make their conservation both dynamic and problematic.

Key words: climate variation, penguins, population change