Table 1.

Comparison of the concentration of chemical volatiles in the secretions of antibiotic-treated (AB), saline water-treated (SA) and uninjected (NAT) nestlings of the same brood. (The paired comparisons for phenol (in parentheses) were analysed with the sign test owing to the high rate of zeros in the two groups. Compounds are numbered in elution order from descriptive analyses (appendix S1, electronic supplementary material).)

	Friedman ANOVA n = 6, d.f. = 2		Wilcoxon matched pairs test
	χ2	p-value	AB-SA, p-value (n = 7)	AB-NAT, p-value (n = 6)	SA-NAT, p-value (n = 6)
(1) butanoic acid	9.33	0.009	0.018	0.028	0.345
(2) 2-methyl butanoic acid	7.91	0.019	0.018	0.043	0.753
(4) benzaldehyde	4.33	0.115	0.310	0.345	0.345
(5) phenol	3.00	0.223	(0.480)	(0.480)	(0.480)
(6) 4-methyl pentanoic acid	8.44	0.015	0.028	0.028	0.345
(7) phenyl acetaldehyde	2.33	0.311	0.128	0.116	0.916
(8) unidentified	7.64	0.022	0.018	0.046	0.144
(9) indole	9.00	0.011	0.018	0.028	0.600
(10) 3-phenyl propanoic acid	8.09	0.018	0.018	0.043	0.917
(11) 4-chloro indole	7.91	0.019	0.028	0.028	0.917