In the following we briefly analyze and compare voice (including mechanical sound of wings) of two closely related Pitta species, African Pitta (Pitta angolensis) and Green-breasted Pitta (Pitta reichenowi). We also try to quantify the extent of vocal differences using the criteria proposed by Tobias et al. (2010), as a support for any taxonomic review.
We have made use of sound recordings available on-line from Xeno Canto (XC), the Macaulay Library (ML), Avian Vocalizations Center (AVoCet) and The Internet Bird Collection (IBC).
African Pitta: Song during display is a combination of a wing noise (two low-pitched 'notes') and a whistle, uttered simultaneously with exactly the same start time.
Figure 1: Wing noise and whistle of African Pitta (Pitta angolensis)
Green-breasted Pitta: Song is a periodic whistle "o-whuu" or "o-whu-o", there is clearly no synchronization with the periodic wing-noise.
Figure 2 and 3: Whistle resp. wing noise of Green-breasted Pitta (Pitta reichenowi)
In the following we summarize some measurements of basic parameters:
|African Pitta (n=4)||Green-breasted Pitta (n=4)|
|amplitude ratio||50-90% (2nd 'note' weaker)||80- 90% (2nd 'note' weaker)|
|length first 'note'||0.040-0.048s||0.040-0.048s|
|length 2nd note||0.03-0.04s||0.030-0.037s|
|shape||curly rising with hook at end||S-shape or hat-shape|
From the above measurements, it appears that the main vocal differences of Green-breasted Pitta (vs. African Pitta) are:
the single whistle is longer in duration (score 2-3) and has a lower maximum frequency and overall frequency range (score 2-3), and the note shape is different (score 1). Wing-noise apparently is performed at lower frequency (score 2). There is apparently no synchronization between wing-noise and whistle.
This results in a total score for vocal difference of about 5.
This note was finalized on 28th June 2015, using sound recordings available on-line at that moment. We would like to thank in particular the sound recordists who placed their material on XC, ML and AVOcet, Jesse Fagan, Kemigisha Harriet, Linda Macaulay, Niall Perrins, Mark Robbins and Derek Solomon.
Tobias, J.A., Seddon, N., Spottiswoode, C.N., Pilgrim, J.D., Fishpool, L.D.C. & Collar, N.J. (2010). Quantitative criteria for species delimitation. Ibis 152(4): 724–746.