Table 1.

Individual pairwise t-tests for four measurements

	ML area	LL area	ML length	MTM length
WCS
9	T = −6.5	T = −3.6	T = −2.7	T = −2.3
	P < 0.001	P < 0.01	P< 0.05	P < 0.05
15	T = −3.1	T = −1.4	T = −0.03	T = −0.21
	P < 0.05	P = 0.19	P = 0.97	P = 0.83
16	T = −2.6	T = 0.38	T = −0.15	T = −2.6
	P < 0.05	P = 0.7	P = 0.88	P < 0.05
11	T = 2.5	T = −0.74	T = 1.39	T = −0.73
	P< 0.05	P = 0.47	P = 0.19	P = 0.47
12	T = 1.9	T = −4.9	T = −1.04	T = 1.03
	P = 0.08	P < 0.001	P = 0.32	P = 0.32
ZF
5	T = −3.54	T = −3.4	T = −2.83	T = −1.5
	P< 0.01	P < 0.01	P < 0.05	P = 0.16
18	T = 1.48	T = −4.2	T = 2.16	T = −1.82
	P = 0.17	P < 0.01	P = 0.058	P = 0.10
20	T = 1.23	T = −4.96	T = 0.29	T = 5.39
	P = 0.24	P< 0.001	P = 0.77	P < 0.001
23	T = −3.59	T = −0.77	T = 0.64	T = −0.06
	P< 0.01	P = 0.46	P = 0.53	P = 0.95
31	T = −0.32	T = 0.70	T = 2.57	T = −0.38
	P = 0.75	P = 0.49	P ≤ 0.05	P = 0.71
21	T = 0.87	T = 4.18	T = 5.95	T = −0.18
	P = 0.4	P < 0.01	P < 0.001	P = 0.86

The measurements of five WCSs and six ZFs were taken at 10 points along the dorso-ventral axis. The 10 measurements from each side of the syrinx were paired and tested for similarity. Negative T values indicate that the measurement on the left side was larger. Significant results (significance level P = 0.05) are indicated in boldface. Numbers in the left column indicate bird identification.