An Emetic Technique to Investigate Food Preferences

An emetic technique to investigate food preferences.--Studies of food preferences of bird species are generally based on contents of preserved stomachs and direct observation in the field.A thorough study often requires sacrificing a number of birds of a population.If other aspects of the species are being investigated simultaneously, if the population under observation is small, and banding or color marking for individual identification is used, then the loss of any individuals may be undesirable.Although the use of emetics on birds is not a widespread technique, this method can provide data on food habits without sacrificing birds.Previous studies involving techniques that do not require sacrificing birds are summarized here, followed by data obtained from the technique that appears most valuable.A technique was developed by Moody (1970, Auk 87: 579) for obtaining stomach contents from insectivorous birds by forcing saline solution through the digestive tract and flushing food material out the cloaca.The application of this technique to granivorous birds by Moody (op.cit.) proved unsuccessful because of impediment of the saline flow by the gizzard.Chaney and Kare (1966, J. Amer.Vet.Med.Assoc.149:938) determined the effects of several emetic substances orally introduced--copper sulfate--or intravenously introduced--copper sulfate, apomorphine, hydergine, and lanatoside C. The results for each of the experimental species--Herring Gull (Larus argentatus), Rock Dove (Columba