To: "michael norris" <>, "Messages Birding-aus" <>
Subject: sparrows
From: "Ricki Coughlan" <>
Date: Mon, 27 Feb 2006 14:31:22 +1100
G'day Michael and all
There were some studies in the UK which stated that chemicals in unleaded petrol were the villains behind the insect reduction in big cities in the UK (I'm not so certain that this study is widely supported or not). It may be that we're experiencing the same thing here. The study which I mentioned in the previous posting involved a hell of a lot of work on insect populations, life cycles and sparrow diet (anyone who has read the paper would agree that the author deserves a medal for her ability to observe the minutiae and wade through so much sparrow faeces). Sparrows may be primarily granivores, but they do supplement with insects and insects play an important role in raising young too.
I still don't think that it is correct to cite a small population of raptors such as Collared Sparrowhawks as being responsible for declines in birds. Especially, as I mentioned in an earlier posting, that we have to take into account that there are many more raptors in the country towns where sparrows thrive. Neither sparrowhawks, or any other raptors, are widespread enough in urban environments to account for the massive and almost uniform disappearance of sparrows. 
Importantly, the role of sparrows, along with doves and pigeons, in most ecologies where they naturally occur is to be food for raptors. Therefore, they have all of the breeding, clutch size, behavioural and social patterns well in place to deal with a couple of local sparrowhawks and then some. What sparrows might not have is the ability to deal with some kind of change in local environments which does not favour them in some way or may expose them to levels of predation which is unprecedented for them. In this case, it could be a combination of environment or competition of some kind and raptors but it would be one of the most unlikely of scenarios that raptors alone are playing a significant role in the demise of the House Sparrow.
Sparrows aside, half your luck for having a breeding pair of Collared Sparrowhawks nearby.
Happy sparrowing
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