In 1978, we initiated a study of the effects of heptachlor-treated cereal grains on wildlife—particularly the Canada Goose (Branta canadensis)—in the Columbia Basin (Blus et al. in Jarvis and Bartonek, Management and Biology of Pacific Flyway Geese, OSU Book Stores, Corvallis, OR, 1979: 105–116).
To assess the impact of heptachlor and other pollutants on the reproductive success of Great Basin Canada Geese (B. c. moffitti), we collected a sample egg for pesticide analysis from each of 41 marked nests on the Umatilla National Wildlife Refuge in Oregon and Washington, and another series about 65 km upstream from Umatilla on the McNary Recreation Area, Washington. In these two arid areas, geese nest on islands in the Columbia River.
Sample eggs collected from three active nests in mid-March were addled, and the contents were gray. We judged that these three eggs were laid during a previous year, since geese in this area initiate laying in early March, and two of the three nests contained unincubated, incomplete clutches that were ultimately completed and incubated.