|
About these various messages. Results from 21 years
of GBS in Canberra suggest that you can't learn very much from just one or two
years of a survey. Bird populations are far too variable and too many factors
are operating. Trying to read too much from too little data is risky. Impacts of
Noisy Miners are localised. See also a paper by Peter Woodall about that. Woodall, P.F. 1996, ?Limits to the distribution of the House
Sparrow Passer domesticus in suburban Brisbane, Australia?, Ibis
138: 337?340. Also in Canberra the increase in the Common
Myna matches exactly in timing to the decrease in the Common Starling (and
possibly the Red-rumped Parrot but no other parrots). This is strong
circumstantial evidence of a connection, not proof. Decrease in House Sparrows
also correlates in time to the increase in the Common Myna and the Crested
Pigeon. The Pied Currawong has on average NOT increased in Canberra. That is
with the extra detail that: yes summer abundance and local breeding of the Pied
Currawong has increased markedly (abundance doubling over 21 years), whereas
winter numbers and flock size has decreased by a much greater amount. It is
their presence and breeding during summer that matters, when they impact on
other birds.
Full details in my GBS Report.
Philip
|
