Thanks Philip for that explanation. I don't get to COG meetings so it is hard
for me to get books. The explanation of competition reducing grey butcherbirds
I think could be a factor. However, currawongs and kookaburras are common down
the coast (eg Ulladulla and Malua Bay) and in Sydney where butcherbirds are
also common. I would say kookaburras are more common in those areas whereas
currawongs may be less common. I like Geoffrey Dabbs explanation the best, I
hope he doesn't mind me mentioning it, but he implies Canberra's lack of
reptiles are the reason 'The Atlas notes that the low GB numbers have been
linked to the city's poor lizard fauna and refers to Roberts CBN 14(2): 34'.
This makes most sense to me. It may also have something to do with habitat or
predation by cats.
A dramatic increase of grey butcherbirds in the last 3 years cannot be
explained by changes in competition, but could be explained by changes in the
legislation on cats with curfews and tougher compliance, less people keeping
cats and more keeping them inside. Changes in cats and habitat (maturing of
bushes and trees) may have also led to an increase in lizard numbers over the
same period.
Benj Whitworth
-----Original Message-----
From: Philip Veerman
Sent: Friday, 18 February 2005 4:14 PM
To: ;
Subject: Grey Butcherbirds in gardens??
Benj and all: See this Extract from my book: "Canberra Birds: A Report on the
first 21 years of the Garden Bird Survey" as follows as usual most issues have
been addressed:
Grey Butcherbird Cracticus torquatus
This is a common species in major east coast cities, yet it is rare in
Canberra. This would suggest that it is not the urban environment itself that
causes the scarcity. In our area it occurs in woodland and along the
Murrumbidgee river corridor. Maybe it is the competition from the abundant Pied
Currawong that impacts adversely on this bird (see also the Laughing Kookaburra
text). Records are mostly of isolated individuals and not many have repeat
observations. So the bird passes through, rather than stays in the urban area.
Numbers are much higher from February to June, than July to January. This may
reflect dispersal during the non-breeding period. Its distribution suddenly
increased from an average of 4.47% for the first 18 years to 10%, 18% then 22%
for the last three years, which created the huge recent abundance increase.
Graphs on page: 103, Rank: 102, A = 0.00310, F = 6.21%, W = 5.1, R = 0.303%, G
= 1.02.
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