Female pied flycatchers choose territory quality and not male characteristics

Female mate choice is central to the theory of sexual selection1, but much of the evidence for the basis of this choice is inconclusive2–4. First, non-random mating may occur because of male-male competition3; and second, even if females can be shown to be choosing mates it is often difficult to tell exactly on what criteria they are choosing. Possible criteria include male genes5–10, parental ability3 and quality of the resources held by males11,12, but in the wild these factors are often interdependent3. Here we report a field experiment with pied flycatchers that eliminates the correlation between male characteristics and territory quality. We find that age, size, plumage colour and song repertoire of males are all uninfluential in female choice, and that territory quality is the single most important criterion.