Relationships of avian cecal lengths to food habits, taxonomic position, and intestinal lengths

Body mass, intestinal lengths, and the occurrence and relative size of ceca from 154 species of birds representing 21 orders and a diversity of food h abits; were compared. Well-developed ceca occur in the Anseriformes, Gallif ormes, Gruiformes, Cuculiformes, Strigiformes, Caprimulgiformes, and Trogon iformes. The presence of well-developed ceca is less consistent in other or ders and appears to be related to diet; herbivorous species whose diets con tain large amounts of cellulose have well-developed ceca, whereas species h aving diets rich in soluble sugars and proteins tend to have poorly-develop ed or no ceca. We postulate that the relatively well-developed ceca in some non-herbivorous birds are associated with conservation of critical resourc es such as water and nitrogen.