PARENT-OFFSPRING INTERACTIONS IN ZEBRA FINCHES

The begging behavior of immature Zebra Finches has both visual and acoustic components. Begging nestlings gape at their parents, exposing characteristic mouth markings and a moving tongue. They also emit begging calls. Both components undergo changes as the offspring mature, and there is a shift from the visual to acoustic modality as the primary stimulus for feeding. Recorded fledgling begging calls were broadcast inside the cages of Zebra Finch parents with offspring. These begging calls stimulated parental feeding and other behaviors associated with feeding. The offspring also responded to recorded calls by showing begging behavior. Parents were sensitive to recorded begging calls from approximately day 16 to day 28 after the first offspring hatched, although there was substantial variation in these times among pairs of parents. Received 1 October 1976, accepted 12 October 1977. AFTER hatching, the offspring of some species of birds are fed by their parents, usually for a period of several weeks. A common feature of the interaction during parental feeding is some type of begging behavior that stimulates parents to provide food to their offspring at a time when it is needed. The details of this communication system can provide information concerning the reproductive strategy of the parents, i.e. the allocation of their "parental investment" (Trivers 1972). We have determined some of the details of the parent-offspring communication system of the Zebra Finch (Poephila guttata). We concentrated on this interaction during parental feeding. Our efforts have followed two approaches: 1) observation of the begging behavior of young Zebra Finches, and 2) observation of the responses of the parents to natural and artificial begging signals. Immelmann (1965) has summarized the breeding biology of wild Zebra Finches. This species breeds readily in captivity. Pairs of birds will initiate reproductive activity year round and produce several clutches in succession. They are disturbed very little by human presence, and for these reasons are appropriate choices for observation and experimentation of avian parent-offspring interaction. Zebra Finches used in these studies were obtained from several breeding stocks. Breeding pairs were housed indoors in 31 x 43 x 61 cm wooden cages with fronts. A 12/12 light-dark regime was used throughout the study; temperature fluctuated between 20 and 25?C. The birds were fed a commercially available finch seed mixture. Grit and broken eggshells were always available. In addition, germinating seeds, bathing water, and a mixture of boiled egg and bread crumbs were provided daily or every other day. The nests were open-topped round containers 10-12 cm in diameter lined with cloth pads. Feeding bouts were observed using a video camera system placed in front of the cage. Lighting was provided by a high intensity desk lamp. Feeding behavior could thus be observed on a television monitor and recorded on videotape for subsequent analysis. The birds quickly accepted the presence of the light and camera. Feeding bouts were systematically recorded during the first hour of the light period. Most pairs began feeding during the first or second day of observation. Prior to many of the recorded feeding bouts, the nestlings were removed, weighed, and placed back into the nest in known positions so that individuals could be identified by position on the television monitor. During feeding bouts nestling begging calls were recorded on a Nagra IV S tape recorder at 19