Nest Building in the Bengalese Finch. I : External Factors Affecting It and Its Relation To Other Behaviour Early in the Breeding Cycle

Abstract

Pairs of Bengalese finches taken direct from stock cages in which the sexes are kept separately vary widely in the time taken to settle down. Birds showing a longer delay until they are prepared to incubate, also spend less time in the nest box soon after pairing and are seen to copulate later. Growth of interest in the nest box after pairing is slowed down when no nest material is provided. The peak period of building in normal pairs occurs in the five or six days prior to the first egg. The female does the majority of building within the nest box; the male does by far the majority of carrying of nest material to it. In normal pairs nest building declines at the start of incubation, but it did not do so in pairs whose nest was removed three times daily. Pairs in this situation would construct a complete nest in a few hours. Singing by males declines at around the start of incubation and is rare when incubation is fully established. The eating of cuttlefish bone by females is almost entirely restricted to the egg-laying period. Only 25% of isolated males build nests, while it is rare for a paired male not to do so. The presence of another bird or birds is the important factor here as groups of four males, monosexual male pairs and males separated from females by bars were all found to build. The results are discussed in relation to previous work on the same species. The controlling influence of external stimuli, whether acting directly on the nervous system or through the mediation of hormones, is stressed.