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Fig. 1.14
Relationship
between mean individual
song diversity and male
population size of Dupont's
lark (
Chersophilus duponti
)
(Reproduced with
permission from Laiolo
et al.
2008
)
There is growing evidence that fragmentation affects not only the distribution
and abundance of species but also their canorous repertoire.
In oscine birds, the cultural transmission of the acoustic repertoire seems a very
efficient tool to reinforce individual and population fitness. The complexity of the
acoustic cues in these animals is manifested across several life traits such as song
rate and spectro-temporal performance.
Dialects represent variation on the geographically spaced theme and are impor-
tant to balance local adaptation in the face of barriers (Laiolo
2008
). Finally, birds
emit with their song honest signals of well-being for local variability.
For instance, Dupont's lark (
Chersophilus duponti
), a threatened lark in South-
ern Europe, is a lark with a patchy distribution in Peninsula Iberica in residual
steppeland. This species persists in open habitats although such are deeply
fragmented by urbanization, road infrastructures, and intensive agriculture. In this
species, studied by Laiolo et al. (
2008
), a significant relationship between the
structure of a landscape and the complexity of its song repertoire has been found.
The overall song diversity results from the variation among populations (beta-
cultural diversity). Song dissimilarity and distance between subpopulations evi-
dently agreed, and the same result was found between individual song diversity and
patch area. A distance of only 5 km was found sufficient to characterize a specific
cultural tradition in song repertoire. The smaller patches had the poorer song
repertoire.
These authors have found that the acoustic repertoire of populations of small size
was related to the dimension of the male population size (Fig.
1.14
). For the first
time, how culture in nonhuman organisms is strictly connected with the structure of
a landscape has been demonstrated. The bioacoustics method utilized is extremely
efficient to detect subtle changes in song repertoire and allows monitoring a
population using a rigorous approach. The dimension of the male population is an
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