Lead Shot and Ducks on Lake Cowal.

Abstract

We determined the amount of lead shot left after shooting, in the sediment and also the occurrence of lead shot in the gizzards of waterfowl shot at Lake Cowal. We also investigated levels of lead in livers. Livers and gizzards of 342 ducks, Pacific black duck (96), grey teal (122), maned duck (102), pink-eared duck (15) and Australasian shoveler (7), were collected during the 1987 duck shooting season. Few birds had ingested shot (1.5%). Black ducks had more grit, the size of shot, in their gizzards than did grey teal or maned duck. Total grit contents in the gizzards were of a similar weight for black duck and maned ducks but less for grey teal. Two ducks had lead levels in the liver indicative of lead poisoning (>6 ppm) wet weight. Lead levels in the liver were generally low, 0.32 � 0.76 ppm (mean + s.d.). There were no differences between species or sexes in levels of lead in livers. There was also no difference between lead levels of ducks shot on opening day compared to those shot 4 weeks later. Crude density estimates, extrapolated from 77 samples of sediment (800 cm2), averaged 16 000 shot per hectare for areas close to where hunters camped. Crude density, extrapolated from 100 samples, was 3400 shot per hectare for areas of low hunter density.