Fig 1.
Representative chromatogram of volatile compounds emitted by the eggs.
Numbers above peaks indicate volatile compounds significantly different between sexes before false discovery rate adjustment (1: pentadecane; 2: tetradecane; 3: (1R,3R,4S)-2,2,4-trimethyl bicyclo[2.2.1]heptan-3-ol; 4: formamide; 5: 5-methyl-3-hexanol; 6: decanal; 7: formic acid; 8: 2-methylpropanoic acid; 9: 5-(dithiolan-3-yl)pentanoic acid; 10: 2-ethylhexanoic acid). Asterisk above peak indicates the volatile compound significantly different between sexes after false discovery rate adjustment.
Fig 2.
Mean (± SE) percentage on total volatile organic compounds (% on total VOCs) in the two sexes (male: dark grey; female: light grey).
Volatile compounds are grouped according to their classes (a. ketones; b. hydrocarbons; c. terpenes; d. ammides; e. alcohols; f. aldehydes; g. free fatty acids). Asterisks indicate significant differences in the concentration of the volatile compounds between sexes. Double asterisks indicate that the volatile compound significantly differed between sexes after false discovery rate adjustment.
Table 1.
Linear mixed models of variation in the concentration of volatile compounds between barn swallow eggs containing embryos of either sex.
Table 2.
Paired t-test of the difference in the concentration of volatile compounds between eggshell halves placed in nests in the cowshed and eggshells kept in the lab.