Gammon, DE, MC Hendrick & MC (2008) Vocal communication in a songbird with a
novel song repertoire. Behaviour 145: 1003-1026.
Why do individuals in many songbird species sing multiple song types?
Previous studies have often described the current utility of possessing a
vocal signal repertoire, but this may not explain why repertoires evolve. We
looked for repertoire function in black-capped chickadee (Poecile
atricapillus) populations with a song type repertoire that is probably
derived from the single song type found in most populations across the
species' geographic range. Through observations of dawn singing, and natural
and simulated territorial countersinging interactions, we tested several
hypotheses on how a repertoire might facilitate improved vocal
communication. We failed to find significant evidence supporting an adaptive
origin for song type repertoires. Although we found that naturally
countersinging males matched song type approximately twice as often as
expected by chance, matching was not associated with conflict escalation in
either natural or simulated contests and, therefore, the exact function of
song type matching in these birds remains unclear. In addition, we found
that novel song types frequently appear in small isolated populations, which
suggests that a repertoire might evolve simply as the nonadaptive result of
imperfect song-learning combined with geographic isolation.
Amorim, MCP & ASM Neves (2008) Male painted gobies (Pomatoschistus pictus)
vocalise to defend territories. Behaviour 145: 1065-1083.
Many fish species emit sounds in agonistic contexts. During direct
confrontations sounds are typically produced during the display phase in
conjunction with visual exhibitions. Here we studied sound production during
territorial defence in captive painted gobies, Pomatoschistus pictus, and
related acoustic parameters with male traits and the date of recording
(Julian day, i.e., with the approach of the peak of the breeding season).
Territorial males emitted drumming sounds during displays that involved
darkening the chin and fins, spreading fins and quivering the body. Drums
were trains of low frequency pulses (?23 pulses) repeated every 27 ms and
usually lasting under a second. Drums were produced in short sequences of
sounds (bursts). All acoustic parameters differed significantly among males.
Drum and burst duration, and drum number of pulses increased significantly
with male size. Calling duration (including drum, burst duration and drum
number of pulses) also increased significantly with Julian date and
presented a high intra-male variability, suggesting that these parameters
may also depend on the individual's motivation. We provide the first report
for agonistic sound production in sand gobies and give evidence that sound
parameters contain information that can be used during mutual assessment in
contests over territories.
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