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Series of calls of the White-tipped Dove. The signal was bandpass-filtered (250 Hz, 800 Hz) and amplified with Raven Pro, Version 1.2.1. DFT size was increased from the standard 512 samples to 2048 samples, to improve frequency resolution.
In most of Brasil, L. rufaxilla has a monosyllabic call, and L. verreauxi has a bisyllabic call (u - uuuuuu) (Sick 1997). Only in the Northeast, it appears that the call of L. verrreauxi is monosyllabic as well (but see below).
According to a recent article by Figueiredo 2008, the length of the interval between consecutive calls is a reliable criterion to tell the two Leptotila species apart, even if both have monosyllabic calls. Intervals of 7 seconds or more would be typical for L. verreauxi, while intervals of 3-6 seconds have been found for L. rufaxilla. See also Gibbs et al. 2001, p. 357.
The series of calls presented here (fig. 1, above) exhibits intercall intervals of about 8 seconds, which suggests L. verreauxi.
This call is not purely monosyllabic. Immediately before each main call (labels "m" in the waveform plot), there is a faint introductory note (labels "s"; see fig. 2 for a more detailed plot). Actually, this introductory note sounds like a remnant of the first note of the bisyllabic call recorded elsewhere in Brasil. This further supports identification as L. verreauxi.
However, purely monosyllabic call series, with intervals of more than 7 seconds, have also been recorded in the study areas. It seems that the "remnant bisyllabic" variant, and the monosyllabic form, are both common.
Labels "o" in the waveform plot designate calls from another individual, possibly responding to the first one. Veja fig. 2 para detalhes da seção marcada "A".Início da página
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Detalhes da seção "A" da fig. 1. Note the introductory faint sound "s". In a given call series, the envelope of the main sound "m" exhibits little variability between successive calls, but it may differ from the envelope seen in other call series (presumably from different individuals). Possibly, interindividual differences in envelope shape serve to identify the caller.
It is unlikely that the faint introductory note can be heard over a long distance.
See also fig. 3.Início da página