J. Podos, A PERFORMANCE CONSTRAINT ON THE EVOLUTION OF TRILLED VOCALIZATIONS INA SONGBIRD FAMILY (PASSERIFORMES, EMBERIZIDAE), Evolution, 51(2), 1997, pp. 537-551
Behavioral evolution can be influenced by constraints, for example, of
phylogeny and performance. In this paper I describe a pattern in the
evolution of birdsongs that may reflect a constraint on vocal performa
nce. Trilled vocalizations from 34 species of songbirds (Passeriformes
: Emberizidae) were analyzed. Two acoustic variables, trill rate and f
requency bandwidth, were measured for different trill types. In most s
pecies, maximal values of frequency bandwidth were found to decrease w
ith increasing trill rates. Further, trills with low trill rates exhib
ited wide variance in frequency bandwidth, and trills with high trill
rates exhibited only narrow frequency bandwidths. The bounded nature o
f this pattern suggests that performance constraints have limited the
evolutionary diversification of trills. In particular, I explore the r
ole of constraints associated with vocal tract modulations during song
production and evolution. Identification of this constraint may enhan
ce our ability to explain particular patterns of trill evolution.