Volatile and semivolatile compounds in gray catbird uropygial secretions vary with age and between breeding and wintering grounds

The uropygial secretions of some bird species contain volatile and semivolatile compounds that are hypothesized to serve as chemical signals. The abundance of secretion components varies with age and season, although these effects have not been investigated in many species. We used solid-phase microextraction headspace sampling and solvent extraction coupled with gas chromatography-mass spectrometry to detect and identify volatile and semivolatile chemical compounds in uropygial secretions of gray catbirds (Dumetella carolinensis). We identified linear and branched saturated carboxylic acids from acetic (C2) through hexacosanoic (C26); linear alcohols from decanol (C10) through docosanol (C22); one aromatic aldehyde; one monounsaturated carboxylic acid; two methyl ketones; and a C28 ester. We tested for the effect of age on signal strength and found that juvenile birds produced greater amounts of volatile C4 through C7 acids and semivolatile C20 through C26 acids, although the variation among individuals was large. Adult birds displayed small concentrations and minimal individual variation among volatile compounds, but produced significantly higher levels of long-chain linear alcohols than juvenile birds. We tested for the effects of season/location by sampling adult catbirds at their Ohio breeding grounds and at their Florida wintering grounds and found that the heaviest carboxylic acids are significantly more abundant in secretions from birds sampled during winter at the Florida site, whereas methyl ketones are more abundant in birds sampled during summer on the Ohio breeding grounds. We observed no effect of sex on semivolatile compounds, but we found a significant effect of sex on levels of carboxylic acids (C4 through C7) for juvenile birds only.