We are currently working on the
echolocation of a bird- AND insect-eating bat, Nyctalus lasiopterus. That
bat emits shallow FM calls over a wider range than other Nyctalus
species. Frequency of max energy varies from 12 to 17 kHz. Although many
things remain unclear, the lowest frequency (12 to 13 kHz) calls are
emitted in circumstances where we believe that bats are foraging for
birds rather than for insects. Conversely, higher frequency (15 to 17
kHz) search sequences were recorded in areas and seasons where
potential insect prey was abundant. From a physical point of view, the
lowest frequency calls should be more efficient in detecting large and
distant objects. However, they could be much more conspicuous to birds.
I have been unable to find clear and general data about bird auditory
sensitivity. Species of interest belong mainly to the genera Erithacus,
Phylloscopus, Sylvia etc. Does somebody here know if the auditory
sensitivity of those species drops significantly more between 12 and 15
kHz than between, e.g., 10 and 12 kHz?
Thanks a lot for your answer(s),
Jean-Francois Julien
Centre de Genetique Moleculaire
C.N.R.S.
1, avenue de la Terrasse
F-91190 Gif sur Yvette
phone: 33 1 69823226
fax: 33 1 69823160
cel.phone: 33 6 68049987
|