Response of woodcocks (Philohela minor) to heptachlor dosage was closely related to the physical condition of the birds, as reflected by body weight and by body weight in relation to capture weight: in a series of tests with underweight birds, nearly all woodcocks died at dosage levels well below those at which nearly all the birds in a normal-weight series lived. Heptachlor residues in tissues were determined and their loss with time was estimated. Dieldrin proved more toxic than heptachlor to birds of similar weight. Birds in good weight survived massive doses of DDT; some succumbed to smaller spaced serial doses, but only when these were accompanied by starvation rations. When birds were placed in foil-lined boxes after doses of heptachlor added to butter oil or corn oil, it became evident that they passed quantities of oil in about 3 hours, thus very likely ridding themselves of a large part of the heptachlor dose. It was concluded that other methods than dosage with encapsulated chemicals would be needed for appraisal of field effects of toxicants on woodcocks.
