THE EFFECT OF PREBREEDING DIET ON REPRODUCTIVE OUTPUT IN ZEBRA FINCHES

Environmental conditions at the time of laying can influence clutch si ze in birds. Here we show that the quality of diet a female bird recei ves before the start of the breeding season also has a profound effect on reproductive output and on body condition after laying the clutch. Female zebra finches Taeniopygia guttata given a brief exposure to a high quality diet before pairing produced larger eggs, larger clutches , had higher hatching success and fledged more young, yet did not lose as much muscle condition as control birds. The emphasis on energetic limitations in avian life history studies may have disguised the impor tance of nutritional factors in clutch determination and female fitnes s.