Variable loadings of male cuckoo calls for four principal components.

The percentages of variation explained by each principal component are given in parenthesis and the component that was loaded most highly for each parameter is in bold. T1 = duration of syllable 1; pause = temporal gap between syllables 1 and 2; T2 = duration of syllable 2; PF1 = peak frequency of syllable 1; PF2 = peak frequency of syllable2; F1H = highest frequency of syllable 1; F2H = highest frequency of syllable 2; F1L = lowest frequency of syllable 1; F2L = lowest frequency of syllable 2. ΔF1 = the difference between the highest and the lowest frequencies of syllable 1; ΔF2 = the difference between the highest and the lowest frequencies of syllable 2; ΔPF = the difference between the peak frequencies of syllables 1 and 2.