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Song following male movement
Direction of male movement after song, relative to border
Direction of male movement before song, relative to border
Direction of male movement after song, relative to female
Direction of male movement before song, relative to female
Song before female movement
Song after female movement
Direction of female movement after song, relative to male
Direction of female movement before song, relative to male
Direction of female movement after song, relative to border
Direction of female movement before song, relative to border
Direction of female movement before song, relative to nest
Song, before interaction
Song, after interaction
Type of interaction
Neighbor's song category.
For each category a specific code was coupled, for instance, at the category
“Song before female movement” the possible codes are 1
¼
last song before
female movement, 2
¼
second to last, 3
¼
third to last, 0
¼
not within three
songs of female movement.
Accented-ending songs were heard in connection with unmated status, and
unaccented-ending songs were associated with singing near territorial borders,
but this author stated that “the predictive power of song category was not absolute,”
but each song category is associated with a set of behavioral possibilities. Further
specific messages are included in the acoustic signal but encoded in a finer level of
signal variation. This work demonstrates how it is possible to explore the complex-
ity of the song repertoire when each type of song produces observable changes in
the behavior of neighbors.
Song categories represent a type of language and can be considered at the top of
a hierarchy of signal organization.
Other playback experiments conducted by Mathevon and Aubin ( 2001 ) have
demonstrated how the blackcap ( Sylvia atricapilla ) is able to decode the sound
signals from conspecifics as an adaptation to the degradation of signals in dense
vegetation.
Manipulated songs to mimic the effect of song degradation by vegetation in a
dense layer of undergrowth were used to examine the responses of blackcap males.
Territory holders replied even to crudely manipulated artificial sound. Only when
the frequency modulation was suppressed or the number of syllables strongly
reduced there was a cessation of male reply to the playback. This species seems
highly tolerant of song structure modification as an adaptation to the propagation of
song in a dense forest environment.
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