| Summary: | Large scale climatic fluctuations, such as the El Niño-Southern
Oscillation (ENSO), can have dramatic effects on ocean ecosystem
productivity. Many mobile species breeding in temperate or higher
latitudes escape the extremes of seasonal climate variation through longdistance, even trans-global migration, but how they deal with, or are
affected by, such longer-phased climate fluctuations is less understood.
To investigate how a long-lived migratory species might respond to such
periodic environmental change we collected and analysed a 13-year
biologging dataset for a trans-equatorial migrant, the Manx shearwater
(Puffinus puffinus). Our primary finding was that in El Niño years, nonbreeding birds were at more northerly (lower) latitudes than in La Niña
years, a response attributable to individual flexibility in migratory
destination. Daily time spent foraging varied in concert with this
latitudinal shift, with birds foraging less in El Niño years. Secondarily, we
found that in subsequent breeding, a hemisphere away, El Niño years
saw a reduction in foraging time and chick provisioning rates: effects
that could not be attributed to conditions at their breeding grounds in
the North Atlantic. Thus, in a highly migratory animal, individuals may
adjust to fluctuating non-breeding conditions, but still experience
cascading carry over effects on subsequent behaviour.
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