Singing rate in relation to breeding stage
Discrete song rate varied significantly among the six breeding stages (Analysis of Deviance: χ2 = 19.65, df = 5, P = 0.0015; Figure 4). Post-hoc linear contrasts showed that discrete song rate did not differ between the breeding and non-breeding seasons (estimate ± SE (log scale): -0.39 ± 1.21; Z = -0.32, P = 0.7489). Within the breeding season, however, discrete song rate was higher for males with no nesting duties than for males with nesting duties (mean of nest building, egg stage, nestling care, and fledgling care; estimate ± SE (log scale): 2.78 ± 0.81; Z = 3.46, P = 0.0005). Discrete song rate also was lower during nestling care than during other nesting stages (mean of nest building, incubation, and fledgling care; estimate ± SE (log scale): -2.87 ± 0.99; Z = 2.89, P = 0.0039).