Effectiveness, Biases and Mortality in the Use of Apomorphine for Determining the Diet of Granivorous Passerines

• Published in: The Condor (Los Angeles, Calif.) Vol. 99; no. 3; pp. 765 - 772
• Main Authors: Valera, Francisco, Gutiérrez, Jose E., Barrios, Rafael
• Format: Journal Article
• Language: English
• Published: Santa Clara, CA Cooper Ornithological Society 01-08-1997; Cooper Ornithological Club; American Ornithological Society
• Subjects: Animal and plant ecology; Animal behavior; Animal, plant and microbial ecology; Animals; Autoecology; Aves; Biological and medical sciences; Bird nesting; Birds; Chicks; Dental calculus; Diet; Emetics; Food; Fringillidae; Fundamental and applied biological sciences. Psychology; General aspects. Techniques; Hardness; Methods and techniques (sampling, tagging, trapping, modelling...); Mortality; Ornithology; Vertebrata; Wild birds; Evaluation; Vertebrata; Diet; Interspecific comparison; Bias; Mortality; Regurgitation; Granivorous; Method; Aves; Feeding; Emetic
• ISSN: 0010-5422; 1938-5129; 2732-4621
• DOI: 10.2307/1370487

We analyze the effectiveness, biases and limitations of a poorly-known emetic, apomorphine, for studying the diet of granivorous birds. Apomorphine was tested on three Fringillids yielding an effectiveness of 43-78%, comparable to that reported for the most common emetic, tartar. The effectiveness of the emetic varied significantly among species, probably due to different physiological tolerances. Older chicks and adults were equally sensitive to apomorphine, but it was ineffective in young chicks. The action of the chemical was not independent of food type, and certain food items were underrepresented with this method. However, the importance of most food categories closely resembled the one found through dissection. Mortality caused by exposure to apomorphine was low (< 3%) and successive applications of apomorphine proved to be innocuous, thus allowing for long term studies. Yet, the effectiveness of apomorphine decreased when administered repeatedly within a short time. Apomorphine is an advisable tool for laboratory and field work on granivorous passerines because it is effective, practically harmless, provides reliable results, and can be used repeatedly and easily both with nestlings and adults.