Birds invent the password!

This is quite outside my normal favourite topics, but it’s so cool I had to share anyway. (Though I guess it’s still not quite as far outside as, say, exoplanets :D)

A study of nesting superb fairy wrens (Colombelli-Négrel et al., 2012) suggests that these beautiful little birds use something akin to a password to defend against cuckoo infiltration. While the female sits on her eggs, she calls to them. The chicks inside listen, and when they hatch, their begging contains sounds that match a characteristic part of mum’s nesting calls. Learning is clearly going on – when you switch eggs between different nests, the chicks’ cries are most similar to their foster mother’s and not their genetic mother’s calls. (So while the technique might work against cuckoos, it’s no good against cuckoldry ;))

(Superb fairy wrens from Wikipedia. Female (left) by Fir0002/Flagstaffotos, male in breeding plumage (right) by JJ Harrison.)

The female uses the same password to tell her mate to feed her, so he also learns. The crucial thing is that cuckoo chicks don’t. Maybe it’s because they hatch earlier; since female fairy wrens stop making their calls when the first egg hatches, a hatchling cuckoo has had less time to memorise them than a hatchling wren. Either way, both parent wrens can tell the difference. By playing back the begging of wren chicks brooded in the target nest, wren chicks from elsewhere, and cuckoo chicks, the researchers determined that the parents react differently to “home” and “foreign” calls. When the begging cries contain the correct password, they feed the chicks more and spend less time on the lookout for intruders. Interestingly, it makes no difference whether the calls are from another wren nest or from a cuckoo. If you got the password wrong it doesn’t matter if it was by one measly typo 🙂

***

Reference:

Colombelli-Négrel D et al., (2012) Embryonic learning of vocal passwords in superb fairy-wrens reveals intruder cuckoo nestlings. Current Biology in press, available online 08/11/2012, doi:10.1016/j.cub.2012.09.025

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