thornbills and cuckoos - some questions [SEC=UNCLASSIFIED]

["Whitworth, Benjamin - BRS" <>]

Another argument is that there is a competitive disadvantage if the host parents become too picky. They may end up kicking their own chicks out by accident if they look a bit different.

Benj

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From: Philip Veerman [
Sent: Monday, 17 September 2007 11:40 AM
To: Con Boekel
Cc:
Subject: [canberrabirds] thornbills and cuckoos - some questions

Con asks: what is the competitive advantage for birds to raise a cuckoo in the nest? Why don't they simply let the cuckoo die?
The question is like: "what is the competitive advantage for zebras being eaten by lions?" They don't know it is a cuckoo. They are confronted by an appealing big mouth. There is no competitive advantage for birds to raise a cuckoo in the nest. For now, the cuckoos have got it over them. However the hosts do have some strategies for picking the difference and rejecting the cuckoo eggs or chicks and the cuckoos have some strategies for getting by the hosts' defensive strategies. So there are patterns of mimicry or detection of mimicry going on. It is an ongoing evolutionary battle that is still in progress. However the competitive advantage is for birds to raise a chick that has a big mouth and successfully begs. Usually that will be their own. The cuckoos have created a super normal stimulus that compels the hosts to feed it.

 

Early nesting may be a strategy that reduces the chance of a particular nest being parasitised. However that will probably vary with geography as the cuckoos are migrants.

 

Philip