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This paper describes the influence of diet on intestinal length of the bulbul Pycnonotus leucogenys. Monthly samples of birds were collected and intestinal length and main food items recorded. The diet varied seasonally with plant material (mainly fruit) dominating in winter and insects in summer. In winter birds had longer intestines than in summer. Since changes in intestine length did not correlate with changes in body weight it seems that birds with a high content of plant material in their diet had longer intestines, and this result is discussed in relation to a theory of optimal digestion.
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Al-Dabbagh et al. (1987) studied this question.
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