As you have pointed out Con, raptors are at the top of the food chain, hence their numbers/density are/is low. For cuckoos to be successful they require a number of hosts/host nests at the appropriate stage to add their own egg. Raptors would
not meet such a requirement. Further, John Harris has just described how 3 Red Wattlebirds harassed the female Koel. If a raptor would harass a cuckoo, the cuckoo may not come off as lightly as probably the female Koel did in John's case.
Michael Lenz
On Fri, 28 Dec 2018 at 16:20, 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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