Some Males are Choosier Than Others: Species Recognition in Blue Waxbills

We investigated whether species specific mating preferences differed between the sexes in three species of blue waxbill (genus Uraeginthus). We compared male preference for conspecific females versus heterospecific blue waxbill females using two-way choice trials. The results were compared with predictions of the strength of species specific mating preferences made on the basis of several different hypotheses. These predictions were made according to the specific behavioural and morphological traits of the three species, their phylogenetic relatedness and relative geographical location. Males did not prefer conspecific females whenever they were given a choice of a larger heterospecific female. Furthermore, males tended to discriminate between females more strongly when there was a large difference in size between the two species of females that they had been presented with. Relating the strength of males preference for conspecific females to the predictions made according to the different hypotheses it appeared that males were discriminating between females on the basis of their size. We compared male mate preferences for conspecifics versus heterospecifics with female mate preferences for conspecifics versus heterospecifics that had been ascertained in a previous study. There were marked differences between preference for conspecifics between the sexes for all three species, suggesting that males and females used different criteria to choose mates when discriminating between related species. Males appeared to use female size whereas females appeared to use the degree of male ornamentation, suggesting that mate preference is under a different selective pressure between the sexes. The results of this study have identified that there is a potential for hybridisation between blue breast females and both red cheek and blue cap males. In the event of a geographical change leading to sympatry between these species the degree of hybridisation will depend on the preference criteria within each species and the differences in morphology between those species. This will ultimately determine how discrimination between heterospecifics will interact with conspecific mate choice.