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Robin
mentions off-chatline dialogue with me, although I didn't offer an opinion then
as to whether they were adults or chicks, more about the aspect of them being
described as solitary in McComas Taylor's "Birds of the ACT" Guide. Robin
suggested "Maybe he's using the term to differentiate from birds that hang
around in a flock". I wonder are they more solitary than the other birds on
that page and if so, why mention it in that book.
I
agree with Geoffrey that I wouldn't go by apparent size, especially as we are
only seeing the head and with no direct comparison. Robin's photos tended to
make me think they are young birds mainly because the plumage appears
fresh and neat. I would expect adults would show more worn plumage. I also see
signs of maybe two ages of feathers in Geoffrey's photos of an adult, that I
don't see in the believed young birds. That seems logical as a distinction. But
I may be wrong.
I can
compare these to the slides I took of owlet nightjars nearly 37 years ago that show
a small grey birdy smudge, that I was pretty proud of at the time.
Philip
I
doubt that apparent size would be much help with these Robin. HANZAB notes
the difficulty of ageing, but says the juveniles have more subdued dark markings
and a more conspicuous orbital ring. Below is an apparent adult from that
site, first picked up on Jack Holland’s ‘nest workshop’ in November 2010.
Below that are 2 apparent juveniles photographed on the date given. Those
2, and your 4, do appear to be young birds on the basis of the HANZAB criteria,
when compared with the first bird below, particularly the muted head
markings.
From: Robin
Eckermann [ Sent: Saturday, 31 December
2011 2:03 PM To:
Subject: [canberrabirds] Re:
Youngsters ... probably!
Further to my posting yesterday, I had some off-chatline
dialogue with Philip Veerman about the picture of two (possibly young) owlet
nightjars. That prompted me to go back and check on an earlier picture of a pair
in the same hollow, taken in early February this year (assuming you get
this before New Year!) I thought folk might be interested in the
comparison ...
When you compare the LHS picture (taken
yesterday) with the older RHS picture, it looks like the birds I saw yesterday
were quite a bit smaller - perhaps reinforcing the hypothesis that they were
quite young birds. The pictures are taken from a different angle, so that's why
the profile of the wood doesn't match exactly.
Regards ... Robin
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