Hi Denis
The bird looks like a two year old female. Black gape, bit of
buff in the plumage, and a bit of streaking in the breast.
Male birds have an all black bill, females have the grey lower
mandible.
A juvenile has completely streaked underparts, a one year old
has heavily streaked breast and flanks.
Birds aged as three years old or older have virtually no
streaking on the breast. At this age the male has white lores.
Cheers
Anthony
From: Denis Wilson [
Sent: Tuesday, 11 December 2007 5:30 PM
To: COG bird discussions
Subject: [canberrabirds] Grey Shrike-thrush - sexual dimorphism, or
juvenile markings?
Is
it possible to distinguish male and female Grey Shrike-thrushes by plumage?
I
found this injured bird on the road, on the weekend. Naturally I took a photo.
I
was intrigued by the fine dark lines on the centres of the chest feathers.
On
line sources (COG gallery, Australian Museum Birds in backyards) make no
mention of sexual dimorphism. However, clearly some birds in the COG gallery have
much whiter faces, and smoother chest colouring than this bird.
This
bird has just the faintest of brown eyebrow markings (trace of juvenile
plumage?). The base of the lower mandible, is grey, not the typical
yellow gape of a recently fledged bird.
Some
photos show clear black beaks, and very smooth, pale grey chests, and white
lores and throat. I take those markings to indicate male birds.
Any
clues as to whether this is a female, or nearly mature juvenile bird?
Incidentally,
as the bird was stunned, (when I found it) but apparently structurally
intact, I released it, after keeping it calm for some time. It had recovered to
the point of hopping actively, but still not flying. I hope it recovered,
but I felt I had little alternative to let it take its chances.
Love
to Grow: Grow to Love