Results of statistical tests on difference between sessions in the morning and afternoon.

The mean proportion of each behavioral index and standard deviation were calculated for sessions in the morning (am) and afternoon (pm). The number of individuals used to calculate mean proportion is shown in the columns ‘n (am/pm)’ (at each age, birds who did not respond to either song were excluded). U and p indicate the statistical value and p-value of Mann-Whitney U tests. (XLSX)