SONG AS A PURSUIT-DETERRENT SIGNAL, AND ITS OCCURRENCE RELATIVE TO OTHER ANTI-PREDATION BEHAVIORS OF SKYLARK (ALAUDA-ARVENSIS) ON ATTACK BYMERLINS (FALCO-COLUMBARIUS)
W. Cresswell, SONG AS A PURSUIT-DETERRENT SIGNAL, AND ITS OCCURRENCE RELATIVE TO OTHER ANTI-PREDATION BEHAVIORS OF SKYLARK (ALAUDA-ARVENSIS) ON ATTACK BYMERLINS (FALCO-COLUMBARIUS), Behavioral ecology and sociobiology, 34(3), 1994, pp. 217-223
Skylarks show a range of anti-predation behaviours including flocking,
refuge-seeking and song. Responses by skylarks to merlin attack were
recorded over three winters on a Scottish estuary to determine the eff
ectiveness of song as a pursuit-deterrent signal, and its use with res
pect to other anti-predation options such as flocking. Mortality due t
o merlin predation was high. Skylarks used song as a pursuit-deterrent
signal. Merlins chased non- or poorly singing skylarks for longer per
iods compared to skylarks that sang well. A merlin was more likely to
catch a non-singing than a poorly singing than a full-singing skylark.
Temperature did not affect chase lengths, song types or success rates
of attacks. Larger flocks of skylarks were preferentially attacked so
that the individual probability of being attacked within some larger
flock sizes was greater than in a smaller flock. Success rate did not
vary with flock size. Merlins chose skylarks before any song was heard
, so there was no cost for non-singing skylarks in joining flocks. The
frequency of capture on merlin attack depended on the escape response
used by the skylark. Non-singing skylarks were probably more likely t
o escape by seeking a refuge or staying on the ground on attack, while
singing skylarks were more likely to escape if they flew. The optimal
escape option available to a skylark on meflin attack was probably de
pendent on its condition, as indicated by its ability to sing on attac
k.