Borg, John J.
To predict the impact of climate change over the whole species distribution range,
comparison of adult survival variations over large spatial scale is of primary concern for
long-lived species populations that are particularly susceptible to decline if adult survival is
reduced. In this study, we estimated and compared adult survival rates between 1989 and
1997 of six populations of Cory’s shearwater (Calonectris diomedea) spread across 4600 km
using capture-recapture models.
We showed that mean annual adult survival rates are different among populations
along a longitudinal gradient and between sexes. Variation in adult survival is synchronized
among populations, with three distinct groups: (1) both females and males of Corsica, Tremiti
and Selvagem (annual survival range 0.88-0.96); (2) both females and males of Frioul and
females from Crete (0.82-0.92); and (3) both females and males of Malta and males from
Crete (0.74-0.88). The total variation accounted for by the common pattern of variation is on
average 71%, suggesting strong environmental forcing. At least 61% of the variation in
survival is explained by the Southern Oscillation Index fluctuations. We suggested that
Atlantic hurricanes and storms during La Niña years may increase adult mortality for Cory’s
shearwater during winter months. For long-lived seabird species, variation in adult survival is
buffered against environmental variability, although extreme climate conditions such as
storms significantly affect adult survival. The effect of climate at large spatial scales on adult
survival during the non-breeding period may lead to synchronization of variation in adult
survival over the species’ range and have large effects on the meta-population trends. One
can thus worry about the future of such long-lived seabirds species under the predictions of
higher frequency of extreme large scale climatic events.