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Fig. 2.1 ( a ) Song post
position of different bird
species in 2010 in
relationship to position in
1986-1989. The line is
y ΒΌ x .( b ) Regression line
and increase in song post
position between
1986-1989 and 2010 in
relationship to population
trend of different species of
birds (Reproduced with
permission from Moller
2010 )
temperature and precipitations have increased by 20 and 30 %, respectively. The
average song post was 18 % higher (1.2 m on average), and this change has been
observed more clearly in species singing in trees when compared with species
living in shrub vegetation. Sexually dichromatic species were found to vary more in
height than monochromatic species, and finally species more susceptible to
sparrowhawk ( Accipiter nisus ) predation were moving less in height than species
that were less susceptible. Also, populations with high density have been found to
move higher in the song posts. In conclusion, species with higher intraspecific
competition, such as dichromatic species and species with populations with higher
density, are more sensitive to the height of the song post: the first type because they
perform a more intense sexual display and the second from the need to reduce
population competition (Fig. 2.1 ). These results suggest that the singing sites of
birds change rapidly, and this variation affects sonic ambience, and consequently
the design of songs, mating success, and prey-predator interactions.
In several insects temperature has a great influence on the biological activity. In
the cicada Diceroprocta olympus (Homoptera: Cicadidae), the hypothesis of ther-
moregulation seems proved by the regression of the T b (body temperature), ambient
temperature ( T a ), and perch temperature ( T p ), but in contrast with other acoustic
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