John
Firstly, refer to Hugo's earlier e-mail about the rate of deaths of waders
being cannon-netted. Deaths among cannon-netted waders can occur in several
ways.
1. Birds can be struck by the rope (not wire) at the leading edge of the
net.
2. Birds can drown if netted in water
3. Birds can become heat affected (I have never personally seen this)
4. Birds can suffer capture myopathy
and although I have, again, never seen it
5. Birds can be taken by predators upon release.
I think Hugo's figures of 4 deaths in a thousand birds captured are probably
about right but you always hear about horror stories occurring in the past.
Cannon-netting licences are VERY hard to come by and those currently holding
them are very conscious of their responsibilities. If they weren't I am
confidant the Australian Bird Banding Scheme and the relevant state
authorities would be very quick to act.
Any deaths are minimised by adhering to a series of protocols.
1. Cannons are set to fire projectiles at a certain angle up and over the
birds. A danger zone is marked out and the person firing the cannons has a
clear view of this danger zone. A line is set within the danger zone and
this is jiggled should there be birds too close to the net. Waders being as
wary as they are, particularly at roost sites soon move away from the
aforementioned giggler. If birds remain in the danger zone the net IS NOT
fired.
2. Avoid firing the net over water whenever possible. If the target
species roosts in shallow water then the net is only fired if there are
sufficient number of experienced people to handle the number of birds in the
capture zone. The net is then ONLY fired on a falling tide. If there are
birds in the water the net is carefully lifted and shuffled back towards dry
sand.
3. Birds held after capture are placed in bottomless, often, hessian cages
set up on the sand. In hot weather canopies are set up over these to
provide shade. The number of birds in each cage, sorted according to
species, are controlled to ensure that overcrowding does not occur.
Immediately following capture the NSW Wader Study Group always covered the
birds in light shade cloth in order to stop the birds struggling as well as
providing cover.
4. Some species, as previously mentioned by others, can suffer capture
myopathy. Susceptible species are removed from the net and processed first.
5. I have never seen a wader taken by a predator upon release. Common
sense should minimise this. Birds are not released while a predator is in
the area. Birds are always released away from the area of activity.
It is always difficult to describe what happens in a cannon-netting event.
There is a checklist that covers each step of the proceedure that ensures
the safety of both operators and birds. As I have said, the birds welfare
is paramount in the minds of the people conducting this work. There are
risks but these are minimised as much as possible. I appreciate that some
individuals will always see these risks as being simply to great and that is
fine. There are others that feel that the value gained from such work
justifies the risks.
I refer people who need clarification of what the value of this work is back
to Hugo's earlier posting.
David (not Andrew) Geering
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
To unsubscribe from this mailing list, send the message
"unsubscribe birding-aus" (no quotes, no Subject line)
to
|
