Abstract and SummaryWhen a mixed pair of one zebra finch (Z) and one Bengalese finch (B) parent raises 2 Z young, the Z parent shows more parental care than the B parent. Three possible hypotheses for this difference are investigated:1— Z parents show more parental care generally, independent of whether the nest contains Z or B young.2— Parents are more stimulated to show parental behaviour by conspecific than by heterospecific young.3— Young have an initial bias to respond preferentially to conspecific parents.The results of an experiment in which mixed pairs raised 1Z + 1B young showed a species‐specific relation in parental behaviour; therefore the first hypothesis can be rejected. Several observations indicate that the species‐specific relation seems to be due to selectivity in the parents of both species and not in the young, making the second hypothesis the most likely one. Literature on other species and functional considerations support this view.Differences were also present in the proportion of allopreening and clumping directed by both parents to the Z and the B young. No direct relation between these differences and the selectivity in parental care