Impact of kin odour on reproduction in zebra finches

Although it has long been disregarded, the accumulating evidence suggests that birds use chemical cues for communication. However, the impact of olfaction on avian mate choice and its potential function in inbreeding avoidance remain unknown. We compared the mate choice and reproductive behaviour between females experimentally deprived of their sense of smell and intact control females. Each female was allowed to mate with two unfamiliar males, an unrelated male and a full brother. If olfactory cues are involved in kin recognition and/or mate choice, we expect the smelling females to reproduce with the unrelated males and the anosmic females to mate randomly with respect to relatedness. The paternity analysis revealed that the anosmic females reproduced randomly with respect to relatedness. Contrary to our expectations, the females with an intact olfactory mucosa demonstrated a decrease in reproduction; they produced significantly fewer eggs than the anosmic females, and the chicks in only one of the cages reached independence. Thus, the female's ability to smell in the presence of the unfamiliar brother had the unexpected effect of impairing the reproductive behaviour of the females. This is the first study to report directly the critical role of olfactory signals in reproduction and its potential function in preventing maladaptive breeding attempts with kin in female songbirds.