SUGHRUE, K.M.*; FRENCH, J.B.; BRITTINGHAM, M.C.; Pennsylvania State University, School of Forest Resources, University Park; USGS – Patuxent Wildlife Research Center, Laurel, MD; Pennsylvania State University, School of Forest Resources, University Park: Morphological and Physiological Effects of the Endocrine-disrupting Contaminant Linuron on the American Goldfinch (Carduelis tristis)

Recent investigations have shown that many commercial insecticides and herbicides have endocrine-disrupting properties. Linuron, a broadleaf herbicide, has been shown to produce anti-androgenic effects and alter thyroid function in mammals. The present study was undertaken to examine the potential effects of linuron on a common passerine, the American goldfinch (Carduelis tristis). Based on its food habits, there is moderate potential for dietary exposure to linuron in this non-target species. Captive goldfinches were fed a seed diet coated with linuron for 14 weeks during the pre-alternate molt. Birds received approximately 0, 1, 4 or 16 µg linuron/g body weight/day as calculated by food consumption rates. At 3-week intervals, weight, bill color change, and molt progression were measured, and blood samples were collected. The highest dose of this herbicide caused a transient increase (p<0.05) in body weight at 3 weeks, and both the intermediate and high dose delayed molt (days and intensity to peak molt). Testosterone concentrations of male birds did not differ among groups, however the seasonal testosterone peak level was lowest for the 16 µg linuron/g bw/d group. In addition, the hematocrit of male birds exposed to 4 or 16 µg linuron/g bw/d was less (p<0.05) than controls at the seasonal peak. These morphological and physiological changes indicate that linuron is affecting endocrine-related endpoints at relatively low exposure levels. Whether such changes would impact life-history aspects, such as mating behavior and reproduction, remains unclear.