No effect of heavy metal content on the external morphology of first-year wintering Willow Tits Poecile montanus

Abstract

Previous studies have shown that elevated levels of heavy metals may give reduced growth and shorter wings, whereas other studies gave no detectable effects. I examined the possible effects of exposure to the heavy metals, cadmium (Cd), copper (Cu) and zinc (Zn), on the morphology (lengths of wing, tail and tarsus, and body mass) of first-year wintering sedentary Willow Tits Poecile montanus near a refuse power plant in Trondheim, central Norway, in 1993-2000. The concentrations of Cd and Zn in the liver of the birds varied insignificantly from one year to another, whereas Cu varied significantly, suggesting that the Willow Tits were exposed to metal pollution. No significant correlations were found between the concentration of the metals and the lengths of the wing, tail and tarsus, or the body mass of the birds. Morphological measurements of the Willow Tits living near the power plant were compared with those of Willow Tits wintering at two other sites 3 and 90 km, respectively, from the power plant. Wing length, tail length, tarsus length and body mass did not differ significantly in the study sites, indicating that pollution by the heavy metals investigated did not affect the morphology of the Willow Tits.