Erwin A. P. Ripmeester, Jet S. Kok, Jacco C. van Rijssel & Hans Slabbekoorn
(2009): Habitat-related birdsong divergence: a multi-level study on the
influence of territory density and ambient noise in European blackbirds.
Behav. Ecol. Sociobiol. 64 (3), 409-418.
Abstract: Song plays an important role in avian communication and acoustic
variation is important at both the individual and population level.
Habitat-related variation between populations in particular can reflect
adaptations to the environment accumulated over generations, but this may
not always be the case. In this study, we test whether variation between
individuals matches local conditions with respect to noise level and
territory density to examine whether short-term flexibility could contribute
to song divergence at the population level. We conducted a case study on an
urban and forest population of the European blackbird and show divergence at
the population level (i.e. across habitats) in blackbird song, anthropogenic
noise level and territory density. Unlike in several other species, we found
a lack of any correlation at the individual level (i.e. across individuals)
between song features and ambient noise. This suggests species-specific
causal explanations for noise-dependent song differentiation which are
likely associated with variation in song-copying behaviour or feedback
constraints related to variable singing styles. On the other hand, we found
that at the level of individual territories, temporal features, but not
spectral ones, are correlated to territory density and seasonality. This
suggests that short-term individual variation can indeed contribute to
habitat-dependent divergence at the population level. As this may undermine
the potential role for song as a population marker, we conclude that more
investigations on individual song flexibility are required for a better
understanding of the impact of population-level song divergence on
hybridisation and speciation.
URL: http://www.springerlink.com/content/w3k0vl1r38304706/
For reprints please contact E. A. P. Ripmeester (email:
Michael S. Reichert (2009): Aggressive thresholds in Dendropsophus
ebraccatus: habituation and sensitization to different call types. Behav.
Ecol. Sociobiol. 64 (4), 529-539.
Abstract: Males in many chorusing anuran species use aggressive calls during
defense of calling spaces from other males. The minimal intensity of another
male?s vocalizations that elicits an aggressive call response has been
termed the aggressive threshold. Previous studies of aggressive thresholds
have shown that they are plastic: males habituated (increased their
aggressive thresholds) in response to repeated presentation of stimuli above
initial threshold levels. Habituation likely contributes to the stable
chorus structure of these species, in which aggressive calling is rare
compared to advertisement calls. I have observed high levels of aggressive
calling in the treefrog Dendropsophus ebraccatus, suggesting that males of
this species do not habituate. In this study, I investigated the plasticity
of aggressive thresholds in D. ebraccatus. I measured the aggressive
thresholds of males before and after suprathreshold stimulation by both
advertisement and aggressive calls. I found that the different call types
had different effects: males habituated to advertisement calls but lowered
their aggressive thresholds in response to aggressive calls. I consider the
latter response to be an example of sensitization, a behavior that has been
documented infrequently in vocalizing anurans. Sensitization is a plausible
mechanism responsible for the high levels of aggressive calling observed in
this species. Given the high costs of aggressive calling, however, it is
unclear why a mechanism that increases aggressive call output would be
maintained.
URL: http://www.springerlink.com/content/32756335282370w0/
For reprints please contact M. S. Reichert (email:
Brandon C. Wheeler (2009): Production and perception of situationally
variable alarm calls in wild tufted capuchin monkeys (Cebus apella
nigritus). Behav. Ecol. Sociobiol. 64 (6), 989-1000.
Abstract: Many mammalian and avian species produce conspicuous vocalizations
upon encountering a predator, but vary their calling based on risk urgency
and/or predator type. Calls falling into the latter category are termed
?functionally referential? if they also elicit predator-appropriate
reactions in listeners. Functionally referential alarm calling has been well
documented in a number of Old World monkeys and lemurs, but evidence among
Neotropical primates is limited. This study investigates the alarm call
system of tufted capuchin monkeys (Cebus apella nigritus) by examining
responses to predator and snake decoys encountered at various distances
(reflecting differences in risk urgency). Observations in natural situations
were conducted to determine if predator-associated calls were given in
additional contexts. Results indicate the use of three call types. ?Barks?
are elicited exclusively by aerial threats, but the call most commonly given
to terrestrial threats (the ?hiccup?) is given in nonpredatory contexts. The
rate in which this latter call is produced reflects risk urgency. Playbacks
of these two call types indicate that each elicits appropriate antipredator
behaviors. The third call type, the ?peep,? seems to be specific to
terrestrial threats, but it is unknown if the call elicits predator-specific
responses. ?Barks? are thus functionally referential aerial predator calls,
while ?hiccups? are better seen as generalized disturbance calls which
reflect risk urgency. Further evidence is needed to draw conclusions
regarding the ?peep.? These results add to the evidence that functionally
referential aerial predator alarm calls are ubiquitous in primates, but that
noncatarrhine primates use generalized disturbance calls in response to
terrestrial threats.
URL: http://www.springerlink.com/content/3620710458728425/
For reprints please contact B. C. Wheeler (email:
Julia Bartmess-LeVasseur, Carrie L. Branch, Sheri A. Browning, Jessica L.
Owens & Todd M. Freeberg (2009): Predator stimuli and calling behavior of
Carolina chickadees (Poecile carolinensis), tufted titmice (Baeolophus
bicolor), and white-breasted nuthatches (Sitta carolinensis). Behav. Ecol.
Sociobiol. 64 (7), 1187-1198.
Abstract: Evidence from different chickadee species (Poecile genus)
indicates that birds can modify the note composition of their ?chick-a-dee?
calls in the presence of predator stimuli. Here, we tested the effects of
predator models and the distance of those models on calls of three species
foraging together at feeding stations: Carolina chickadees (Poecile
carolinensis) and tufted titmice (Baeolophus bicolor), both members of the
Paridae family, and white-breasted nuthatches (Sitta carolinensis), a member
of the Sittidae family. Model and distance affected seed-taking rates in all
three species. ?Chick-a-dee? calling rates were higher in the predator
context for both chickadees and titmice, but we detected no predator context
effects on ?quank? call rates for nuthatches. Predator and distance contexts
affected acoustic parameters of notes of the ?chick-a-dee? calls of
chickadees and titmice; no such effects were detected for nuthatch ?quank?
calls. These results suggest species differences in encoding of information
in the primary social calls of these three species that commonly occur in
multi-species flocks. Chickadees and titmice are ?nuclear? species and
nuthatches are ?satellite? species, and these different roles might be
related to the differences in vocal signaling that we detected.
URL: http://www.springerlink.com/content/w796vq7jmq3p8127/
For reprints please contact T. M. Freeberg (email:
Kind regards
Sonja Amoser
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Dr. Sonja Amoser
Steinrieglstraße 286
3400 Weidlingbach
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