Erin H. Gillam, Gary F. McCracken, John K. Westbrook, Ya-Fu Lee,
Michael L. Jensen & Ben B. Balsley (2009): Bats aloft: variability in
echolocation call structure at high altitudes. Behav. Ecol. Sociobiol. 64
(1), 69-79.
Abstract: Bats alter their echolocation in response to changes in ecological
and behavioral conditions, but little is known about how they adjust call
structure in response to changes in altitude. We examined altitudinal
variation in the echolocation of Brazilian free-tailed bats, Tadarida
brasiliensis, a species known to fly to altitudes of 3,000 m above the
ground. From 50.2 h of recordings, we analyzed 113 high-quality echolocation
call sequences recorded from 0 to 862 m above ground level. Bats flying near
the ground used shorter, higher-frequency, broader-bandwidth calls compared
to bats at higher altitudes, an effect likely due to the greater levels of
echo-producing clutter (i.e., vegetation, buildings) found near the ground.
When ground-level recordings are excluded, bats continue to shift towards
the use of longer-duration, lower-frequency, narrower-bandwidth calls with
increasing altitude. We propose that the observed high-altitude changes in
call structure are a response to changing acoustic attenuation rates and/or
decreasing insect densities at higher altitudes.
URL: http://www.springerlink.com/content/y628310364m41348/abstract/
For reprints please contact E. H. Gillam (email:
Holly L. Hennin, Nicole K. S. Barker, David W. Bradley & Daniel J. Mennill
(2009): Bachelor and paired male rufous-and-white wrens use different
singing strategies. Behav. Ecol. Sociobiol. 64 (2), 151-159.
Abstract: To attract a breeding partner, males may behave differently when
they are bachelors compared to when they are paired. Comparisons between
groups of paired males versus groups of unpaired males in temperate-breeding
animals have revealed such differences in signalling behaviour. Few studies,
however, have explored how individual males alter their signalling behaviour
with changes in pairing status, and very few investigations have explored
paired versus unpaired male behaviour in tropical animals. During a 5-year
study in Costa Rica, we analysed changes in the singing behaviour of male
rufous-and-white wrens (Thryothorus rufalbus) when they were paired and when
they were bachelors. We compared three aspects of male vocal behaviour:
gross differences in song output, variation in repertoire use and
differences in song structure. Males as bachelors had significantly higher
song output and switched song types less frequently. Contrary to our
expectation, bachelors sang significantly fewer song types from their
repertoire compared to when those same males had a breeding partner. Songs
sung by bachelor males were higher in syllabic diversity and had
broader-bandwidth terminal syllables than the songs those males sang only
when paired. Within song types, the fine structure of songs remained
consistent across pairing status. Our results demonstrate that males change
their singing behaviour with pairing status, delivering songs at a higher
rate but with less variety when they are bachelors. Rufous-and-white wrens
are renowned for their vocal duets, and we discuss the pattern of repertoire
use in light of their duetting behaviour. These results enhance our
understanding of how male behaviour varies with pairing status and the
importance of vocal signalling behaviour in socially monogamous tropical
animals.
URL: http://www.springerlink.com/content/bh4162211890032p/
For reprints please contact H. L. Hennin (email:
Nicole Geberzahn, Wolfgang Goymann, Christina Muck & Carel ten Cate (2009):
Females alter their song when challenged in a sex-role reversed bird
species. Behav. Ecol. Sociobiol. 64 (2), 193-204.
Abstract: Birdsong serves to attract mates and to deter territorial rivals.
Even though song is not restricted to males, this dual function has almost
exclusively been demonstrated for male song. To test the generality of
hypotheses on birdsong, we investigated female song in the sex-role
reversed, classically polyandrous African black coucal (Centropus grillii)
in the context of female?female competition. We compared spontaneously
vocalizing females with females vocally responding to a playback simulating
a conspecific intruder. Females changed vocal parameters in response to
playbacks: They lowered the pitch of their vocalizations and enhanced the
duration of song elements when being challenged. Also, the composition of
the vocalizations was altered. There was no significant correlation between
pitch and body size parameters in spontaneous song, but there was for
response songs, with larger females having a lower pitch. These changes in
vocal properties suggest that the vocalizations are important for mutual
assessment of competitive abilities in females. Our findings confirm the
general role of intrasexual competition in vocal communication of birds.
URL: http://www.springerlink.com/content/976470p7v2386n43/
For reprints please contact N. Geberzahn (email:
Rindy C. Anderson (2009): Operant conditioning and copulation solicitation
display assays reveal a stable preference for local song by female swamp
sparrows Melospiza Georgiana. Behav. Ecol. Sociobiol. 64 (2), 215-223.
Abstract: Operant conditioning assays are increasingly being used to test
mating signal preferences in female birds. Operant behavior may be seen as
farther removed from mate choice behavior as compared to other methods for
measuring mating signal preferences, which could limit the evolutionary
interpretation of operant results. I compared the song preferences of female
swamp sparrows (Melospiza georgiana) as measured both by a copulation
solicitation display assay and by an operant preference test. Both methods
revealed a strong preference for songs from the females' Conneaut Marsh
breeding population over songs from a Millbrook population over 500 km
distant, which remained stable after extensive exposure to Millbrook songs.
Further, there was a striking congruence in results on an individual level
from the two assays. These findings support the conclusion that operant
methods reveal evolutionarily significant mate choice preferences, providing
the opportunity to study such preferences under circumstances when the
copulation solicitation assay is less practical.
URL: http://www.springerlink.com/content/h106241266084434/
For reprints please contact R. C. Anderson (email:
Kind regards
Sonja Amoser
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Dr. Sonja Amoser
Steinrieglstraße 286
3400 Weidlingbach
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