Factors associated with song perch height
We estimated song perch heights for 6,793 of the 17,682 (34%) songs recorded. Males sang from a wide range of perch heights (5 ± 3 m; 1–17 m; Table 1, Figure S1), but rarely sang from the tallest available perches (15 ± 4 m; 9–22 m; Table 1). Song perch height varied significantly among the six breeding stages (Analysis of Deviance: χ2 = 25.05, df = 5, P = 0.0001) and between the two song types (χ2 = 8.01, df = 1, P = 0.0047). Post-hoc linear contrasts showed that song perches were significantly higher during the breeding season than during the non-breeding season (estimate ± SE (log scale): 1.12 ± 0.50; Z = 2.27, P = 0.0235; Figure 5A), and significantly higher for breeding males with no nesting duties than for breeding males with nesting duties (estimate ± SE (log scale): 0.88 ± 0.27; Z = 3.25, P = 0.0012; Figure 5B). Song perch height also differed significantly between rambling and discrete songs (χ2 = 8.01, df = 1, P = 0.0047), with males singing rambling songs from significantly lower perches (estimate ± SE (log scale): -0.11 ± 0.04; Z = -2.83, P = 0.0047; Figure 5C.).