NUTRIENT PHYSIOLOGY OF THE BLUE-NAPED MOU SEBIRD (UROCOLIUS-MACROURUSPULCHER)

Blue-naped Mousebirds were fed with four different diets: I. mixed foo d (bananas, salad, boiled eggs, boiled rice, apples); II. bananas only ; III. soft fruits (pears and peaches); and IV. food enriched with pro tein (curd cheese and egg white). The minimal times for food passage t hrough the digestive tract were 6-18 min altogether. This is similar t o the data known from nectarivorous birds (< 15 min). The intestines a re extremely short (19,0 +/- 2,4 cm; n = 16) and simple-structured, Wi thout specialization and without any caeca. The overall efficiency for the diets with 71,0 %, ranging between 65,9 % (bananas) and 74,0 % (m ixed food), is relatively low However, for frugivorous birds in genera l, far lower efficiencies are recorded (30-70 %). The assimilation eff iciencies of nutrients depend on their amount in food and the physiolo gical and seasonal requirements. The composition of the assimilated fo od shows that carbohydrates, having the largest part with 89,0-91,1 %, are most important for energy supply. Presumably, the birds utilize o nly sugars being easy to digest, because cellulose is removed. Fat and protein are playing a subordinate role in metabolism. The metabolic t urnover differs with the diet and ranges between 62,5 J/g.h (bananas), 69,2 J/g.h (fruits), 87,3 J/g.h (protein food) and 99,6 J/g.h (mixed food).