Petrels feeding on Antarctic Krill Euphausia superba use two basic strategi
es to locate prey patches. One strategy is area-restricted search, in which
individuals interrupt straight-line motion on detecting prey, and then cir
cle about. This increased rate of turning near prey increases the likelihoo
d of detecting additional patches, since patches tend to be clumped in spac
e. A second strategy is local enhancement, in which individuals monitor the
behaviour of others, and converge on those individuals that display behavi
our indicative of feeding. In this paper, attention is focused on the first
strategy, area restricted search, and evidence of increased turning rates
in the vicinity of krill patches is sought. The hypotheses tested were firs
t, that six species of krill-feeding petrels engage in area restricted sear
ch; and then that the tendency for seabirds to either sit on the water, pat
ter with their feet, or seize prey was correlated with the distance to the
nearest krill patch. Seabird abundance and behaviour was paired with krill
abundance east of South Georgia (55 degrees S, 35 degrees W) in June 1993.
Three species, Cape Petrel Daption capense, Northern Giant Petrel Macronect
es halli and Southern Giant Petrel M. giganteus, changed their direction of
Eight significantly more often when near krill swarms than when in krill-f
ree areas, indicating that they used area restricted search. Cape Petrels w
ere also significantly more likely to sit on the water and to patter along
the surface when close to krill swarms.