Post-copulatory sexual selection and the Zebra Finch

Abstract

The Zebra Finch Taeniopygia guttata is a model passerine and since the mid-1980s my research group has studied both domesticated birds in captivity, and wild birds in Australia, as part of a program of research designed to explore the adaptive significance and underlying mechanisms of sperm competition in birds. Extra-pair courtship is common in wild Zebra Finches, but rarely leads to mounting and as a result extra-pair paternity is infrequent, a result consistent with male Zebra Finch reproductive anatomy. Nonetheless, the species has proved to be an excellent model for sperm competition studies because its basic reproductive anatomy and reproductive processes are similar to other birds. The outcome of sperm competition in the Zebra Finch and other birds is best predicted by the passive sperm loss model, allowing for differences in sperm numbers and quality (fertilising capacity). Last male sperm precedence is not a ‘rule’ in birds but is a consequence of the way sperm competition experiments have been conducted. Several male reproductive traits, including sperm size and velocity in the Zebra Finch have a genetic basis, and, as the Zebra Finch genome project gains momentum, the genes for these traits will be identified.‘Zebra Finches are often taken for granted by Australians because they are numerous, noisy and persistent, but many, including myself, admire them because they typify the “little Australian battler”—the small and insignificant, that somehow succeeds by simply hanging on and enduring the vicissitudes of the vast, harsh country of inland Australia.’ (Richard Zann, ‘The Zebra Finch’, 1996)