Of course Con is right. In the theoretical evolutionary world, why not a meat
eating cuckoo? Maybe there is one already somewhere.
But I took the original question to be why don't Koels, in particular,
parasitize raptors. Hence my musing that diet had something to do with it.
Koels are designed to eat fruit and it is a bit hard to imagine a koel chick
with its unsuitable bill tearing apart a small mammal delivered by the parent.
Philip informed us that a Channel-billed Cuckoo has been known to parasitize a
Sparrowhawk but that sort of proves the point. CB Cuckoos do eat a mixed diet
which includes small birds etc and they are better equipped as chicks to eat
whatever the raptor parent provides. Thus they do tend to parasitize carnivores.
On 28/12/18, 4:21 pm, "Con Boekel" <> wrote:
I don't know the answer but the question intriques:
In terms of size. the Channel-billed Cuckoo is larger than quite a few
Australian raptores.
In terms of diet, why not a meat-eating cuckoo?
In terms of raptors predating/killing the cuckoo, current species of
cuckoos routinely evade/avoid their hosts, why not evolve to be able to
evade/avoid raptors?
One possibility is that raptors are the highest trophic level and there
is not enough energy to go around to maintain raptors AND
raptor-specific cuckoos.
regards
Con
On 12/28/2018 1:56 PM, Philip Veerman wrote:
> Cuckoos parasitise species smaller than themselves. Maybe that is needed
to get the chicks the ability to push the host chicks out of the nest. So just
on that basis there is not much option to target raptors. I don't know if that
is the complete reason. That is not to suggest that this has always been the
case through history or will remain so into the future. One rare quoted example
though is that the Channel-billed Cuckoo has been recorded to parasitise the
Collared Sparrowhawk. Size difference still applies. All other examples I know
of include passerines.
>
> Philip
>
> -----Original Message-----
> From: Con Boekel
> Sent: Friday, 28 December, 2018 12:23 PM
> To: canberrabirds chatline
> Subject: [canberrabirds] Why don't cuckoos...
>
> Geoffrey's musings reminded me of a stray thought occasioned by the
> larger than usual numbers of Koels lurking visually but not vocally in
> Upper Turner this year.
>
> One sighting involved several Koels and a Collared Sparrowhawk in the
> same tree at the same time.
>
> Here is my question: 'Why don't cuckoos parasitize raptores?'
>
> regards
>
> Con
>
>
>
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