Tawny owl at roost in woodland (captive bird) © Wayne Hutchinson / Farm Images / Getty
It is well known that male tawnies hoot to advertise that they have occupied a territory. However, the structure of the hoot differs between individuals, and male tawnies have been found to react more strongly to the calls of strangers than those of known neighbours. This shows that the owls can identify other individuals from their call.
But calls don’t just reveal identity or the holding of a territory. Indeed, evidence suggests that the owl’s vocalisations can impart all sorts of additional information to rivals or prospective mates about the quality of the bird itself.
For example, the pitch of the call is related to the owl’s size, and the final vibrato is longer in larger males than in smaller ones. Males carrying a larger number of blood parasites have calls with a reduced number of frequencies, and a study has revealed that the calls of successful males contain longer notes than those of their less-successful peers.
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