Yup,
They're Common Swifts - Apus apus. I once heard an interview with people who
had claimed that they hated having Swifts nest in their house because of the
constant and irritating screaming noise. This is a sound I have a nostaligic
association with form my childhood and has become less familiar over the
years.
The sparrow issue is fascinating. Just before I left the UK, the RSPB had
commissioned a study to look into catastrophic declines in urban areas. The
species is all but extinct, like so many other species, in farmland, but in
cities has thrived until recently. No-one really knows why. This 'suicidal
tendency' might not be as daft as it sounds. If it is what I think they are
getting at, the same thing can happen in other colonial species. Spoonbills
for example in northern Europe were thriving at a small number of colonies
which were all but wiped out, resulting in a mass dispersal of birds and a
dilution of the population. It is thought to be an evolutionary response to
environmental pressure. For the Spoonbills, it meant a slow increase in
population as many smaller colonies were set up elsewhere - they now breed
in England for example. If this is a similar case for Sparrows but
macro-environmental pressures are too great to find alternative sites, you
might expect a sudden population crash I suppose.
What these things do illustrate is that the environment, at least in the
short term, is a lot more sensitive than we give it credit for.
Relationships between predator/prey etc are never linear and hidden problems
can become critical well before we realise.
Regards,
Simon.
Regards,
Simon.
_____________________________________________
Simon Mustoe - Director
AES Applied Ecology Solutions Pty Ltd.
59 Joan Avenue
Ferntree Gully
Melbourne
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