Ecologists
from Woods Hole Oceanographic Institution in the US and the French National
Center for Scientific Research (CNRS) studied a population of black-browed
albatross at Kerguelen Island, part of the French Southern and Antarctic Lands,
where 200 breeding pairs have been monitored annually since 1979.
Reaching
a wingspan of 2.5 metres, Black-browed Albatrosses breed on these sub-Antarctic
islands during the austral summer, laying a single egg in October that will
hatch in December. The chicks fledge in late March at a size similar to that of
an adult.
Climate
affects this seabird species in complex ways. In this study, the researchers
developed a matrix population model that takes account of the combined effects
of climate variables and functional traits in order to understand the entire
life cycle and how population growth may be affected in light of a changing
climate. Functional traits such as body size, timing of breeding, and foraging
behaviour all have an impact on demographic traits such as survival and
reproduction.
They
found that changes in sea surface temperature during late winter cause the
biggest variations in the population growth rate, through their impact on
juvenile survival during their first year at sea. The effects of climatic
conditions on seabirds generally occur indirectly.
"Sea
surface temperature is widely used as an indicator of food availability for
marine predators because warmer temperatures usually result in lower primary
productivity in marine ecosystems, ultimately reducing the availability of
prey", said Dr Stéphanie Jenouvrier, a seabird ecologist at Woods Hole
Oceanographic Institution.
