Biology Reference
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2.5
r
= 0.488,
P
< 0.001
1.5
0.5
−0.5
−1.5
−2.5
−2
−1.5
−1 −0.5 0
Relative flight feather length
0.5
1
1.5
2
2.5
Fig. 7.5
Song rate compared against flight feather length in the eastern kingbird (
Tyrannus
tyrannus
) (Reproduced with permission from Murphy et al.
2008
)
Moller (
1991
) in which this behavior is interpreted as a paternity guard to reduce the
risk of cuckoldry. During the fertile period the volume of song at dawn
remained low.
The chiffchaff seems to not use the song as a paternity-guard mechanism, but
singing activity has an intersexual function during the fertile period. In fact, the
chiffchaff has a higher song rate at dawn; this song rate decreases after establish-
ment of the pair, and song volume is low during the fertile period. The male uses
several song spots after the fertile period to attract more females. The function of
song activity after the fertile period could be as an intrasexual signal to inform other
males about the territory. This song activity can also be used to have easier access to
re-mating after nest predation or female desertion, reducing simultaneously the
effort of territory patrolling.
Summary
Choruses are one of the most mysterious and spectacular acoustic phenomena
common to terrestrial and aquatic biomes. Choruses are the result of contemporary
vocalization of several individuals and species at a precise time of the day (dawn or
dusk). Most of the vocal animals have choruses. Choruses are an involuntary source
of orientation for pelagic larvae during their definitive settlement along coasts and
coral reefs.
Several hypotheses have been presented in recent years. First, the beginning of
chorus activity is species specific and can be explained with body size and eye size.
The species able to capture more light at dawn (such as the blackbird) are the first
singers.
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