Wax esters of uropygial gland secretion as biomarkers of endocrine disruption in birds exposed to treated sewage water.

The chemical composition of the uropygial gland secretion of birds shows seasonal, sex and age-related variations following sex hormones fluctuations. We explore the use of the composition of the uropygial gland secretion as a non-invasive biomarker of endocrine disruption in 137 common moorhens (Gallinula chloropus) from Navaseca Pond, which receives the effluent of a wastewater treatment plant, and from the more pristine Tablas de Daimiel National Park in Spain. Wax ester and fatty acid compositions were measured by means gas chromatography - mass spectrometry (GC-MS) in the uropygial gland secretion of moorhens from both wetlands. Organochlorine compounds (p,p'-DDE and PCBs) were measured in blood and uropygial gland secretion of moorhens as indicators of anthropogenic pollutants, and this information was interpreted together with previous results of the accumulation of metals and metalloids in blood and feathers of these moorhens and a wide range of endocrine disrupting chemicals (EDCs) measured in water from both study sites. PCBs and p,p'-DDE were found in 32% of the blood and 51% of uropygial gland secretion samples, being at highest levels in Navaseca. Wax composition was dominated by monoesters of 35-38 carbons and displayed a clear seasonal variation, in which long-chain wax esters were more abundant in spring-summer than in autumn-winter. This seasonal change was less evident in birds from Navaseca, where the presence of shorter wax esters was associated with the higher concentration of PCBs in uropygial gland secretion. The observed effect may not be associated with this specific type of pollutants because moorhens in Navaseca are also exposed to a wide diversity endocrine disruptors as shown in a previous study. Uropygial gland secretion can be a useful non-invasive sample for integrating chemical monitoring of pollutants and their effects as endocrine disruptors in birds.