Table 1.

Vocal changes during crowing development. (Comparison between the first crows produced by the quails (column ‘beginning’) and the last crows produced at the end of the experiment (column ‘end’). Component PCA: component matrix of the principal component analysis calculated using spectral features only. Last column: percentage of syllables that do exhibit an increase for each spectral feature.)

			component PCA
acoustic feature	beginning (mean±s.e.)	end (mean±s.e.)	1	2	3	%
T13 (ms)	289.87±16.13	342.68±12.75
S3 (ms)	364.18±27.07	444.3±20.44
TD (ms)	655.05±30.59	786.98±26.42
mean FM	39.85±1.68	46.70±1.81	0.88	0.29	−0.24	95
mean AM	0.03±0.001	0.04±0.001	0.75	0.63	−0.09	80
mean entropy	−4.17±0.32	−3.79±0.38	0.7	−0.61	0.01	85
mean frequency (Hz)	2592.21±116.91	3141.76±331.35	0.83	−0.39	0.28	85
variance FM	573.11±24.05	569.44±18.43	−0.16	0.46	0.81	40
variance AM	0.03±0.001	0.04±0.001	0.75	0.61	−0.11	75
variance entropy	0.66±0.10	0.70±0.09	0.02	0.75	0.25	65
variance mean frequency (kHz)	339.76±23.16	573.48±120.68	0.62	−0.61	0.41	80