FEEDING ECOLOGY OF THE BENGALEE, LONCHURA STRIATA VAR. DOMESTICA (ESTRILDIDAE)
Japanese Journal of Ornithology
In my previous paper dealing with the amount of the two kinds of foods fed to the nestling of the Bengalee Lonchura striata var. domestica by the parents, I reported that the marked difference between the pattern of change in the amount of the seed of the foxtail millet fed to the nestlings and that of the leaf of the cabbage was recognized (SUZUKI 1967). The parent birds spend more time for the feeding activity during the nestling period than during any other periods. If there exists an
... time and energy budget for various activities of a species in a given environment (ORIANS 1961) , it must also be seen in the case of feeding activity during the nestling period. The behaviour of the Great Tit feeding the young was reported by ROYAMA (1966 ROYAMA ( , 1970 . The time budgets of various birds during the breeding period have been studied by several workers (ORIANS 1961 , SCHARTZ and ZIMMERMAN 1971 , VERBEEK 1972 and VERNER 1965 in the field. However, the time expenditure on feeding and the change in the amount of time spent every day during the nestling period have not been estimated sufficiently. As the ability of the thermoregulation of the nestlings of the altricial bird only gradually develops after hatching, the parent bird must brood them for some time of a day or all day long until they become to be able to control their body temperature by themselves. If other conditions such as food availability are favourable, the time of brooding by the parent in which heat is supplied to the nestling may be particularly dependent on the ability of the thermoregulation of it, the brood size, nest construction and the air temperature. During the nestling period, a pair of bengalee must spend some time of a day on the self-maintenance and the brooding and some of the remaining on taking foods for the nestlings. This paper, following the previous one, deals with the time expenditure and its change of the parent bengalees during the nestling period. METHODS The Bengalees used, the method for rearing birds and the experimental conditions were the same as those mentioned in my previous paper (SUZUKI 1976) . Measurement of brooding time. Parent Bengalees brood their nestlings by turns in the daytime or lighted time, and sleep together in a nest in the night or dark time. The brooding time was measured with a wrist watch on the minute basis for an hour for one nest every nestling day, and the maximum number of nests on which measurements were made in a day was eight. The brooding time for an hour was multiplied by 14 to get that for the whole lighting time. Thus calculated value was regarded as the amount of time spent in brooding in the daytime. The parents sometimes fed nestlings while brooding and/or brooded while feeding. In such cases it was difficult to divide the activity of the parents into brooding and feeding. The brooding time stated here means the duration when at least one parent was present in a bottle-shaped nest. Therefore some overestimation would occur especially in the later period when the parent seldom broods. Measurement of time expended on food collection. Time spent in taking food was measured by a stop watch on 0.2-second basis on the birds raising the nestlings. When a bird continuously took more than ten seeds, the number of the seeds taken and the time spent in taking them were recorded at the same time.