Sorry but I don’t believe I suggested that it
was not possible to distinguish the sexes of juvenile Koels this early.
I don’t know either way about that and I specifically was not interested in contemplating what sex “Kevin” is. I did say that the growth process is the same in both sexes.
I have noticed that the young birds appear to get darker as they grow. The point I was making is that and following HANZAB, that as the feathers and the bird grows, you see more of the feathers than the mostly pale tips. Indeed it is quite possible that when
these chicks fledge from the nest, that much of the feathers have still not even fully opened from the pin stage, and all that we see is the distal half or third of the feather.
I think I am seeing in Geoffrey’s article (that sorry I was not aware of before) that it is mostly describing older birds, presumably a year old, that show
mostly adult plumages but still with a mix of retained juvenile plumages.
Although I think the section 2.4 is about these younger juveniles and is relevant. From that I think I see the idea of a very young bird may be growing new
upper wing coverts that may be black in young males. This is interesting and strange, and with it that there may be a second process happening to contribute to them looking darker, if that is what is happening. My earlier message was about the overall change
in appearance as they grow, not particularly about any upper black wing coverts and I stand by that observation.
Philip
From: John Harris [
Sent: Thursday, 30 January, 2020 5:21 PM
To: chatline
Cc: Geoffrey Dabb
Subject: Re: [canberrabirds] Juvenile Koel saga part 3
I am no longer sure that I was as enlightened as I thought I was by Philip Veerman’s detailed explanation that it was not possible to distinguish the sexes of juvenile Koels
this early. I still think my juvenile Koel, Kevin, is male.
I have read Geoffrey Dabb’s excellent, methodical and well-illustrated piece on Juvenile Koels in CBN 43/2.
In his article, Geoffrey clearly demonstrates the emergence of black upper wing coverts in Juveniles in the ACT before departing north. These are very clear in the colour
illustrations in the online version. This is exactly what I have been observing.
At first I just reported a general darkening without trying to be more specific. After I read Geoffrey’s article I managed a more careful look. From my back patio I look
down on the fruiting plum trees and so I tend to see the Koel from above, which is the view from which I observed what I called ‘darkening’. That terminology may be scientifically imprecise but getting a good view through binoculars I saw the upper black wing
coverts beginning to extend downwards over the mottled feathers.
So Kevin is developing black upper wing coverts.
So Kevin is male.
I apologise to Keven for doubting him.
John
From: Philip Veerman <>
Date: Wednesday, 29 January 2020 at 10:02 am
To: John Harris <>
Subject: RE: [canberrabirds] Juvenile Koel saga part 3
Good & thanks…..
From: John Harris [
Sent: Wednesday, 29 January, 2020 9:26 AM
To: Philip Veerman; 'chatline'
Subject: Re: [canberrabirds] Juvenile Koel saga part 3
Thank you Philip, for enlightening us all. You are, of course right. However, I willl continue to call him/her Kevin.
From: Philip Veerman <>
Sent: Tuesday, January 28, 2020 5:28:20 PM
To: John Harris <>; 'chatline' <>
Subject: RE: [canberrabirds] Juvenile Koel saga part 3
I was not comfortable with the idea that “I suspect it is a male as it seems to be darkening over the past few weeks
suggesting that the new feathers coming are dark”. Yes of course it could be a male - 50/50 chance of that. So sex is not the issue. The following text applies equally to
young males and females. Just on first principles, there is no reason that a young bird that is only a few months old will be getting new feathers. That would be really odd and not make any sense. Maybe someone might know a bird somewhere that does this, but
I don’t……. It should be close to a year old before it starts getting new feathers. So I checked the pictures and text in HANZAB. I offer this explanation.
I note HANZAB shows an illustration of “juvenile (still growing) and juvenile (fully grown)” (plate 35, V 4. Page 768). There aren’t many HANZAB plates that
show that distinction, so there will have been a reason.) John’s observation about becoming darker is correct (even without the “seems to”) but the conclusion is not correct. A clue comes from House Sparrows and Starlings that become darker for the breeding
season. This is not through new feathers but through feather wear. Another strong hint is that each year we usually get to see some young male Koels (about a year old) that still have juvenile feathers in wings and tail. That would hardly happen if they were
already growing adult feathers at 2 months old.
What is happening that John describes is the darkening is real but this is not new feathers replacing old. Because of the way body feathers are arranged like
tiles, in an intact bird, we normally see only the tips of the feathers. The whitish spots at the tips will still be there (although they might get frayed off a bit too which would expose the darker parts of feathers below. – but if they were new adult feathers
and it was a male, they would be black). What John is seeing is all those feathers are still growing. The bases of the feathers are darker than the tips. As the feathers grow, instead of just seeing the pale tips of the back and wing feathers, over time, we
see more of the middle and sometimes the bases of these feathers as they reach full size. This is also contributed to by that the total size of the bird increases as it grows, which means it stretches out and so we see more of the darker middle and base of
the feathers than just the pale tips, thus making the bird overall look darker. So this is a growth process, not a process of new feathers causing the change.
Philip
From: John Harris [
Sent: Tuesday, 28 January, 2020 2:06 PM
To: chatline
Subject: [canberrabirds] Juvenile Koel saga part 3
The juvenile Koel is now an independent feeder. It still squawks but no Wattlebirds come to it and it gives up and eats more plums. Before squawking hopefully again. It has begun to eat elderberries as well,
as the branches of the elderberry intertwine with the plum. I suspect it is a male as it seems to be darkening over the past few weeks suggesting that the new feathers coming are dark.
The adult male Koel is still hanging around in a nearby tree
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