The question is what was the sparrow population like before the raptor
population crashed with the introduction of DDT ... presumably there
was a predator prey balance before humanity intervened.
Regards, Laurie.
On Thursday, May 15, 2003, at 10:58 PM, wrote:
I'm amazed that the UK story about the House Sparrow decline
does not mention Sparrowhawks Accipter nisus.
They got that name for good reasons. And the decline stated
in the article corresponds well with the rise in the UK
Sparrowhawk population which had crashed due to DDT etc.
When the Sparrowhawks returned to London in the 1980s I
found the first pair on Hampstead Heath. Soon there were two
or three breeding pairs with 3 to 5 young per nest and small
birds were much quieter. I calculated from the published
data that they would be consuming thousands of small birds
each year. I saw them hunting and in street trees outside
our flat at least 3 kms away from the nest sites.
We bird lovers can overlook what avian predators can do. I
did an analysis of the decline in the Common Bronzewing
population in the City of Bayside. It coincided with some
Pindone oats poisoning of rabbits, mulching over areas with
seed falls... But I've only recently realised that our
Collared Sparrowhawks will take birds as large as
Bronzewings (see the Pizzey and Knight field guide).
I've yet to check the stats. and will try to let you know my
conclusions.
But I certainly do not start with the prejudices about
predator/prey relationships meaning that predators cannot
exterminate one of their prey species. Look at what Homo
sapiens has done.
Michael Norris
Birding-Aus is on the Web at
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