Largely because a lot of wattlebirds deaths are due to predation. And that is true of most species.
I can also mention that Koels are not aware of the breeding of their usual hosts that occur prior to their arrivals.
From: Martin Butterfield [
Sent: Tuesday, 7 November, 2023 4:06 PM
To:
Cc: Philip Veerman; COG bird list
Subject: Re: [Canberrabirds] Koel arrives in bottom end of Higgins
Thanks for that Jack. It does raise the question whether anyone has calculated a 'demographic balance' of Red Wattlebirds? By this I mean Opening Stock of adults + chicks hatched - bird deaths =
Closing Stock. My guess is that the opening and closing stocks are similar in magnitude so with the number of hatchlings being high there must be a balancing high number of deaths. Why are we not knee-deep in dead wattlebirds?
On Tue, 7 Nov 2023 at 15:57, <> wrote:
As mentioned in my November Gang-gang column “with the relatively late arrival (of the Eastern Koel which is still largely ko-eling, ie calling for females, in my local and other
areas) it is unlikely that many RWBs will host Koels in their second brood hatching around December, more likely their third brood around late January/early February.” This is when most Koel fledglings have been historically reported, though in the bumper
and very late 2020-2021 breeding season, where double the number were reported compared with any other season so far, many were probably raised in the 4th RWB brood for the season (see CBN,
46, 119-144 (2021). As shown by Michael Lenz in the same issue of CBN [46, 171-198 (2021)], this does not mean that RWBs will breed every time in these periods, which very roughly span about every 6 weeks from early September to mid-March. As
noted in my November Gang-gang column this is a major reason why local RWBs remain a successful species despite being heavily parasitised by Koels. Jack Holland
From: Canberrabirds <>
On Behalf Of Martin Butterfield via Canberrabirds
Sent: Tuesday, November 7, 2023 3:14 PM
To: Philip Veerman <>
Cc: COG bird list <>
Subject: Re: [Canberrabirds] Koel arrives in bottom end of Higgins
I believe there was a view at an early stage of the Koel invasion that Koels were targeting the second broods since the Wattlebirds, having
satisfied their biological imperative to reproduce with the first brood, would be less determined to defend the second brood.
On Tue, 7 Nov 2023 at 13:26, Philip Veerman <> wrote:
The suggestion (not new) that
their target hosts seem to be breeding earlier each year is interesting. Their target hosts here are Red Wattlebirds, so they could well be starting early, to get their first
batch fledged. A change may also be helped by increasing temperature. In other places they have more hosts. However Red Wattlebirds will often have a second brood, so whilst the Koels might not be able to take on the first RW brood, there is still opportunities
to get the next one.
Philip
From: Canberrabirds
[
On Behalf Of tlann rail via Canberrabirds
Sent: Tuesday, 7 November, 2023 8:56 AM
To: CanberraBirds email list
Subject: [Canberrabirds] Koel arrives in bottom end of Higgins
Heard a male koel calling in Higgins for the first time this spring. As their target hosts seem to be breeding earlier each year, koel numbers here may decline unless they decide
to stay here over winter.
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