Environmental pollutants in the eggs of Welsh Dipper; Cinclus cinclus: a potential monitor of organochlorine and mercury contamination in upland rivers

Deserted or addled eggs (n = 63) were collected from 34 nests of the Dipper Cinclus cinclus in Wales during 1988, while 14 eggs were collected from 8 nests of the Grey Wagtail Motacilla cinerea. A minority of eggs contained HCH and HCB, and only one Dipper egg contained mercury, but all or most contained HEOD, DDE and PCBs. Geometric mean concentrations in Dipper eggs were 3.26 p.p.m. lipid for HEOD, 4.51 p.p.m . for DDE, and 17.78 p.p.m. for PCBs. Concentrations in Grey Wagtail eggs were only slightly higher. In 7 clutches of 3 or more Dipper eggs, within clutch variation was greater than between clutch variation. For clutches of 2 eggs or more, there was significant variation between clutches for HEOD and DDE, but not PCBs. Most variation in DDE levels was due to low values at high altitude sites in upland sheepwalk, whilst high PCB values were found in 2 afforested catchments. Concentrations of DDE in Dipper eggs were generally lower than those in raptors, but HEOD and PCB levels were similar to or slightly higher than in some raptors in Britain, and insectivorous waterbirds elsewhere. The potentail value of Dippers as indicators of organochlorine contamination in upland rivers is discussed.