The Occurrence and Effects of Cadmium Uptake in American Woodcock, Scolopax minor

Date of Completion

January 2011


Agriculture, Wildlife Management|Environmental Health




American woodcock (Scolopax minor) have been experiencing a long-term population decline throughout their range. While habitat loss and human hunter harvest have been investigated as contributing factors in this decline, the potential role of contaminant exposure has not been adequately examined. Cadmium (Cd) is a non-essential metal with a variety of known and suspected effects including alteration/suppression of immune functions and interference with normal testicular function. The woodcock's dietary preference for earthworms which tolerate Cd accumulation, provide woodcock with a potential source for exposure to harmful chemicals. The current literature lacks information on the presence and distribution of Cd in woodcock tissues and its potential effects on immune response and/or male reproductive indices. ^ In order to determine the presence and distribution of Cd in woodcock tissues I solicited carcass donations from volunteer hunters in Connecticut, from which I removed and analyzed liver, kidney, pectoral muscle, and spleen tissues for Cd concentrations. Using cells isolated from fresh-collected spleens from wild woodcock, I conducted bioassays to determine the effects of Cd exposure on immune response as measured by splenocyte proliferation, viability, and progress through the cell cycle. Male reproductive capacity was measured by examining and categorizing, by light microscopy, sections of testes from male woodcock collected during active courtship display. These categories were then tested against the concentration of Cd in liver and kidney and the concentration of testosterone in blood from the same individual. ^ Cadmium concentrations in 99% of livers and kidneys analyzed were above background levels. Thirty percent of kidneys exceeded 100 μ/g Cd dry weight (DW), reported to cause tissue damage in other bird species. Cadmium exposure reduced woodcock splenocyte proliferation at concentrations above 2.5 ppm, reduced splenocyte viability at concentrations above 8 ppm, and altered cell cycle progress at 10 and 15 ppm, when compared to unexposed controls. Cadmium concentrations in liver and kidney from natural exposure were not correlated with reproductive indices such as blood testosterone concentration or testicular histopathology. ^ Woodcock are being exposed to elevated environmental Cd, which could be impairing immune functions, but does not appear to affect reproductive capacity in males. ^