FEEDING INTERRUPTIONS, DIURNAL MASS CHANGES AND DAILY ROUTINES OF BEHAVIOR IN THE ZEBRA FINCH

We investigated daily changes in body mass, fat reserves and crop cont ents, and diurnal organization of behaviour, in the zebra finch, Taeni opygia guttata, in relation to experimental manipulations of food avai lability. Diurnal mass change and the organization of foraging behavio ur during the day were in general agreement with recent theoretical pr edictions. Foraging intensity, and hence rate of mass gain, was most r apid immediately after dawn and before dusk. The experimental birds di d not alter either mean body mass or their diurnal mass trajectory aft er a period of 2 weeks when food was made unavailable for 2 h a day at unpredictable times. Instead, they changed their allocation of time t o different activities during the day, decreasing the mean amount of t ime spent locomoting and increasing the mean amount of time spent inac tive over the day. Thus, contrary to a number of recent studies on dif ferent species, zebra finches appear to respond to unpredictable inter ruptions in food supply by reducing energetically expensive activities rather than adjusting their levels of energy reserves. (C) 1998 The A ssociation for the Study of Animal Behaviour.