From: martin butterfield
[
Sent: Saturday, 15 January 2011 11:28 AM
To: COG List
Subject: [canberrabirds] "Ageing" of Australasian grebes
I have put quotes around the word ageing since this is
whether it is possible to estimate the age of young Australasian Grebes, rather
than their aging process. On 25 November last year I observed 1 adult and
3 young Australasian grebes on our top dam. Some pictures from that day
are in http://franmart.blogspot.com/2010/11/australasian-grebes-on-top-dam.html
Today, 15 January, I was in the area again (primarily improving some blackberry
regrowth) and found that there were still one adult and 3 young grebes: see
attached image taken on full zoom across a hazy dam.
My expectation is that these are a second brood. Does anyone know how
quickly the chicks would grow? Is it more likely that in two months the
first brood:
- became ex-grebes (the area is well supplied with
raptors and foxes are not unknown in the area) and a second started from
scratch; or
- achieved independence and departed while the
excellent season (the area around the dam is lush with vegetation full of
frogs and insects) allowed the second brood?
Martin
