Methylmercury accumulates in food chains of birds and is deposited in eggs. Results from captive breeding studies with Mallards (Anas platyrhynchos) have been used to establish a threshold of mercury in bird eggs that causes harm. Unfortunately, very little is known about the reproductive effects of mercury on wild birds, largely because of the great difficulty and expense of breeding them in captivity. As a practical substitute for captive breeding studies, we developed a technique for injecting the eggs of wild birds with methylmercury and measuring the effects on embryo survival. The eggs of many wild birds were collected in the field, and various doses of methylmercury were injected into the eggs. With game farm Mallard eggs hatching success was 76% for controls, and 56, 62, 53, 44, and 29% for eggs injected with 0.1, 0.2, 0.4, 0.8, and 1.6 ppm mercury, respectively. However, with White Ibis (Eudocimus albus) eggs, hatching success was 62% for controls and 10,25, and 20% for eggs injected with 0.2, 0.4, and 0.8 ppm mercury, respectively. Eggs of some wild birds such as the Ibis proved to be more sensitive to methylmercury than were the eggs of Mallards. Estimates of harmful levels of mercury in eggs, which have been based on reproductive trials with Mallards in the lab, may have to be re-evaluated using techniques such as egg injections.
Additional Publication Details
The use of wild bird eggs to measure the sensitivity of avian embryos to methylmercury
Wilson Ornithological Society and Association of Field Ornithologists Joint Meeting, April 21-24, Beltsville, Maryland. Abstracts