cl - Clumsy

The visual-defect caused by this mutant was reported by Hollander (1938), who found disturbed arrangement of the retinal oil droplets. Hollander studied the mutant and produced fair amount of breeding data when he was a college student. According to Hollander the squabs couldn’t learn to pick up a grain on the floor, and they were always bumbling around. Clumsy pigeons may see close objects fairly well but do not have clear distance vision and they often looked as if the eye is a bit too large. However, an external examination of the eyes of a live bird, even with a magnifying lens, fails to show any apparent defects. Feed is best provided in a bowl or cup. Hollander’s breeding data showed that the inheritance is simple recessive, non-sex-linked; gene symbol cl was proposed. Hollander also reports that pairs of clumsy birds have produced a squab with normal vision – a very unexpected result for a simple recessive gene, which he had no explanation. In his book, Origins and Excursions in Pigeon Genetics, Hollander also reports that although food-blind (also known as feed-blind – simple non-sex-linked gene) showed similar appearance of clumsy, they proved to be caused by two different genes; a cross of a feed-blind cock with a clumsy hen produced only normal progeny. (Hollander, Origins and Excursions in Pigeon Genetics, P.107-108).

According to Levi, the abnormal (clumsy) birds resemble a blind pigeon in their actions. Walking, they grope their way; flying, they crash into objects (when they are forced to fly); eating, they fumble their food. It seemed they could see a little bit but their vision was exceedingly limited (Levi, The pigeon P. 336).

In an article written by Hollander and Miller in 1981, Hereditary variants of behavior and vision in the pigeon, they suggested that investigations of structure and function (by psychologists, neurologists, and others), especially of those dealing with the eye and the brain, should recognize the basic role of heredity and take advantage of revelations afforded by genetic variance. “In pigeon studies to date, this aspect has received almost no attention, probably because of tradition but also because information has been scattered and not conveniently accessible. It is to be hoped that this survey will aid researches in exploiting hereditary variants. The clumsy mutant, for example, may provide novel insight into the organization of the retina. In psychopharmacology, limitation of tests to a single breed can possibly yield very atypical data, or at least will afford no concept of the range of response in the species” (Hollander, W. F. and Miller, Hereditary variants of behavior and vision in the pigeon).

Copyright January, 2013 by Arif Mümtaz.

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