UNDIRECTED SONG ENCOURAGES THE BREEDING FEMALE ZEBRA FINCH TO REMAIN IN THE NEST

Wild zebra finches sing frequently during the breeding season, but the vast majority of song is of the undirected song type that is not dire cted at any individual, and the function of which is obscure - it appe ars to be ignored by all potential recipients. It is sung close to the nest-site, has a peak in production during the egg-laying period, and diminishes thereafter. The incidence of undirected song is positively correlated with extra-pair courtship, a finding consistent with the h ypothesis that it is a means of advertising availability for extra-pai r matings. Typically, undirected song occurred outside the nest when t he female was inside, and a positive relationship was found between th e amount of singing given by die male during the 5-min interval immedi ately after the female entered the nest and the time she subsequently spent inside the nest. Keeping the partner inside the nest during her fertile period is an advantage to the male: it serves as a form of pat ernity protection against other males and it allows him opportunities to pursue his own extra-pair matings. Occupancy of the nest during lay ing is also a means of guarding against intraspecific brood parasitism , which was high at this colony.