Elisabeth Bolund, Holger Schielzeth & Wolfgang Forstmeier (2012): Singing
activity stimulates partner reproductive investment rather than increasing
paternity success in zebra finches. Behav. Ecol. Sociobiol. 66(6), 975-984.
Abstract: Song is used as a signal in sexual selection in a wide range of
taxa. In birds, males of many species continue to sing after pair formation.
It has been suggested that a high song output after pair formation might
serve to attract extra-pair females and to minimise their own partner?s
interest in extra-pair copulations. A non-exclusive alternative function
that has received only scant attention is that the amount of song might
stimulate the own female?s investment into eggs in a quantitative way. We
address these hypotheses in a captive population of zebra finches,
Taeniopygia guttata, by relating male undirected song output (i.e.
non-courtship song) to male egg siring success and female reproductive
investment in two different set-ups. When allowed to breed in aviaries,
males with the highest song output were no more attractive than others to
females in an analysis of 4,294 extra-pair courtships involving 164
different males, and they also did not sire more offspring (both trends were
against the expectation). When breeding in cages with two different partners
subsequently, females produced larger eggs with more orange yolks when
paired to a male with a high song output. These findings suggest that
singing activity in paired zebra finch males might primarily function to
stimulate the partner and not to attract extra-pair females
URL: http://link.springer.com/article/10.1007%2Fs00265-012-1346-z
For reprints please contact Elisabeth Bolund (email:
Lasse Jakobsen, Elisabeth K. V. Kalko & Annemarie Surlykke (2012):
Echolocation beam shape in emballonurid bats, Saccopteryx bilineata and
Cormura brevirostris. Behav. Ecol. Sociobiol. 66(11), 1493-1502.
Abstract: The shape of the sonar beam plays a crucial role in how
echolocating bats perceive their surroundings. Signal design may thus be
adapted to optimize beam shape to a given context. Studies suggest that this
is indeed true for vespertilionid bats, but little is known from the
remaining 16 families of echolocating bats. We investigated the echolocation
beam shape of two species of emballonurid bats, Cormura brevirostris and
Saccopteryx bilineata, while they navigated a large outdoor flight cage on
Barro Colorado Island, Panama. C. brevirostris emitted more directional
signals than did S. bilineata. The difference in directionality was due to a
markedly different energy distribution in the calls. C. brevirostris emitted
two call types, a multiharmonic shallowly frequency-modulated call and a
multiharmonic sweep, both with most energy in the fifth harmonic around 68
kHz. S. bilineata emitted only one call type, multiharmonic shallowly
frequency-modulated calls with most energy in the second harmonic (~46 kHz).
When comparing same harmonic number, the directionality of the calls of the
two bat species was nearly identical. However, the difference in energy
distribution in the calls made the signals emitted by C. brevirostris more
directional overall than those emitted by S. bilineata. We hypothesize that
the upward shift in frequency exhibited by C. brevirostris serves to
increase directionality, in order to generate a less cluttered auditory
scene. The study indicates that emballonurid bats are forced to adjust their
relative harmonic energy instead of adjusting the fundamental frequency, as
the vespertilionids do, presumably due to a less flexible sound production.
URL: http://link.springer.com/article/10.1007%2Fs00265-012-1404-6
For reprints please contact Lasse Jakobson (email:
Christopher N. Templeton, Çaglar Akçay, S. Elizabeth Campbell & Michael D.
Beecher (2012): Soft song is a reliable signal of aggressive intent in song
sparrows. Behav. Ecol. Sociobiol. 66(11), 1503-1509.
Abstract: Animals frequently use signals to modulate aggressive
interactions. Establishing that a signal is aggressive or threatening
requires demonstrating that it is more commonly used in agonistic contexts,
that it predicts subsequent aggressive behaviors by the sender, and that
receivers respond differently to this signal. Like many birds, song sparrows
(Melospiza melodia) produce a low-amplitude ?soft song? vocalization that
has been hypothesized to be an aggressive signal. Soft song meets the first
two criteria, but previous research has failed to demonstrate that soft song
provokes aggression or that receivers even perceive soft song differently
from normal loud song. We used a playback experiment with taxidermic mount
presentation to test whether territorial male song sparrows respond
differently to loud and soft song playbacks. Subjects reacted more strongly
to the soft song playback by approaching the mount more closely, increasing
wing wave displays, and increasing the proportion of their own songs that
were soft songs, with further trends toward increasing the number of flights
and attacks. These results confirm that soft song is a conventional signal
of aggression in song sparrows and that increased receiver retaliation
maintains its reliability.
URL: http://link.springer.com/article/10.1007%2Fs00265-012-1405-5
For reprints please contact Christopher N. Templeton (email:
Katrina M. Schrode, Jessica L. Ward, Alejandro Vélez & Mark A. Bee (2012):
Female preferences for spectral call properties in the western genetic
lineage of Cope's gray treefrog (Hyla chrysoscelis). Behav. Ecol. Sociobiol.
66(12), 1595-1606.
Abstract: Female frogs discriminate among potential mates based on
individual variation in male advertisement calls. While considerable data
have accumulated allowing comparisons of female preference functions among
species, we still lack fundamental knowledge about how and why the shapes of
preference functions for particular call properties vary among populations
within all but a few species. Here, we report results from a study aimed at
describing female preference functions for spectral call properties in
Cope's gray treefrog (Hyla chrysoscelis). Widespread throughout the eastern
half of North America, Cope's gray treefrog is the diploid member of the
cryptic diploid?tetraploid Hyla versicolor species complex, and its
populations are divided into two distinct genetic lineages (eastern and
western). In this study of a western lineage population, we recorded and
analyzed the spectral properties of 1,000 advertisement calls from 50 males
and conducted two-stimulus phonotaxis experiments to estimate a
population-level preference function. Females preferred calls with average
frequencies over calls with frequencies that were 2 or 3 semitones (1.4 or
2.1 standard deviations, respectively) lower than the population mean. We
observed no behavioral discrimination between calls with average and
higher-than-average frequencies. Preferences discriminating against
low-frequency calls were weak and were abolished by attenuating the
preferred average call by 3 dB. We discuss these results in light of
previous studies of eastern lineage populations, geographic variation in
female preference functions, and the potential adaptive value of
discriminating against calls with low frequencies.
URL: http://link.springer.com/article/10.1007/s00265-012-1413-5
For reprints please contact Mark A. Bee (email:
Kind regards
Sonja
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Dr. Sonja Amoser
Steinrieglstraße 286
3400 Weidlingbach
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