It still annoys me when I read criticisms of cannon netting.
I have been a member of 15 or more AWSG North West Wader Expeditions
over the past 20 years as a (paying) volunteer, and I certainly plan
to join future expeditions when I am available. I am not a
bander. I am not the one who summarises the data and publishes
papers. But every expedition I see the dedication of the people who
are involved full time on the study and conservation of
shorebirds. I join each expedition as an assistant, often making the
leg flags, as a spotter in the hide and often the leader of a process
team. I learn more about shorebirds on every expedition that I
join. The shorebird families are always high on my want to see list
when I travel overseas.
I have seen many important and useful outcomes from the expeditions.
A few are :
1. Satellite Tracking of Bar-tailed Godwits. I admit that I was
shocked when I understood how this was done. The waders are caught
in cannon nets (this was not a significant threat and I was part of
the team that made the catch), but then the birds were taken back to
the Broome Bird Observatory where they were surgically implanted with
the transmitters, with the aerial protruding from the tail. Surely
this can't be good? Well all Bar-tailed Godwits survived and were
released, transmitted their data for a year or more (until the
battery gave up) giving important insights into the behaviour and
movement of these birds (local movements, movements within WA,
stopovers for some, feeding stopovers, breeding areas, post breeding
areas), and they were all back in Broome the next year. This was
after this was first done in Alaska, and then in New Zealand so the
people involved had experience with how to look after the
birds. This amount of new information learnt could not have been
achieved in any other way.
2. Satellite Tracking of Little Curlews. Similar to the above, but
the satellite transmitters were attached by harness. Very little
information was previously learnt about this species by band and flag
sightings (mainly local movements) because they are not monitored on
the rest of their migration cycle. So it was not well known where
they stopped over, where they bred, etc. This information was
disseminated very soon after the satellite data was processed every
few days, and it was a major part of BirdLife Australia's event on
increasing the awareness of shorebirds in April this year.
3. Geolocators. This is fascinating. A small one gram device is
attached to a large leg flag. It records the location of the bird at
defined periods for as long as the battery lasts. The difference
from the transmitters is that you must recatch the bird to retrieve
the geolocator to analyse the data. So this has been used on birds
that have a high site fidelity such as Ruddy Turnstone, Greater Sand
Plover and to a lesser extent Red Knot and Great Knot. The results
are amazing and show the migration paths and breeding areas. Some
birds have had a second geolocator attached after the first has been
retrieved, and this allows two years of data to be compared for the
same individual. Do they use the same migration path? Do they use
the same stopover site to refuel? etc, etc.
4. Colour Bands. I admit that I had doubts about the usefulness of
this technique. As part of the Global Flyway Network project,
Bar-tailed Godwits, Great Knots and Red Knots were banded with four
colour bands (two each leg), one yellow leg flag (YLF) and the metal
band. We had been using plain YLFs, and then yellow engraved leg
flags (ELFs) and I thought that this was enough to read the flags to
get the information they wanted. Then as part of the expedition we
spent a day searching for and recording the ELFs and colour bands in
Roebuck Bay. The colour bands are much much easier to read. You can
see them from any angle. You can see then through the legs of other
birds. You can see them from further away. ELFs must be birds in
the open and the flag needs to be side on and you need to be
relatively close to the bird. Three or more people through the GFN
then spend six to eight weeks each year on the feeding sites at the
Yellow Sea monitoring the birds passing through. This gives enormous
information about how and where these birds feed. It shows that you
can't just protect one important area. Birds move between them, and
so you need to protect them all. It gives information on
mortality. It gives information on population sizes. It shows local
movement within Australia, giving information about how some sites
interconnect.
This combination of six items on a bird is the most that I am aware
of. As far as I am aware the most that are used on the smaller
waders (including Curlew Sandpipers) are two legs flags and a metal
band. So when I hear hearsay reports of them having seven items, I
want to see the evidence. Date, place, colours and preferably a
photo. But each time this claim is made, no evidence is produced. So
sorry. I don't believe it.
Without this specific data on the movement of individual birds,
governments won't listen. This data from leg flags and colour bands
puts more pressure on the governments in the flyway to uphold their
obligations under the various migratory bird agreements.
5. Cannon Netting. The teams and the procedures are very experienced
and detailed now. Yes, unfortunately there are still a few birds
injured at the time of firing. And this hurts the members of the
team. These casualties are reported on the catch summary
sheets. The birds are frozen, and sent to the WA Museum. They can't
hide the casualties. There are too many volunteers. I understand
that the 'acceptable' casualty rate is 1%. Maybe early on this
happened. But casualties are uncommon and we usually achieve 0.2 to
0.3% over the course of a three week expedition (about 4,000
birds). With the new small mesh nets, the birds are very quickly
removed from the nets and put in keeping cages covered by shade
cloth. Under the hot conditions at Broome, we need to process and
release the birds within about three hours of the catch. This is
always achieved. Why are the birds caught? Our first goal each year
is to catch enough of 10 key species to be able to estimate the
breeding success (by determining the percentage of juveniles in the
population). This data is important in monitoring rises and
especially falls in the populations. There is a fairly high
recapture rate. These birds give information about the age
distribution of the population and allow better estimations of the
total population. They give information about the movement of the
birds. For some species, it shows that they are quite highly site specific.
6. Blood Samples. I still have some reservations about this. Some
birds do struggle when they are released, and do need to be kept
longer to recover. The blood samples are taken by AQIS for
monitoring avian diseases in Australia. Yes, cloacal swipes are also
taken. During the hysteria of the period when bird flu was an issue,
these samples showed that this was not an issue for Australia. There
are a few casualties of birds that have been bled. Even though this
is not directly due to the normal cannon netting process, they are
included as casualties in the catch report. The government would
want some sort of a measure anyway on avian diseases, so it is better
that the testing is done this way, than through other more drastic
methods one could think of. Only a small percentage of the catch is
sampled, and samples are taken on only a few of the catches in
Broome. Blood sampling in the past has also been used for DNA
analysis, sex determination and other purposes.
7. Isotopic analysis of Feathers. This is fascinating. If you know
when during the migration cycle that a bird grows a particular
feather (say a secondary covert), then by sampling that feather you
can determine to a large extent where the bird was at that
time. This adds to the information from other sources of how birds
move and where they stopover.
8. Declines in Populations. It is claimed that the declines are due
to cannon netting. But this is demonstrably untrue. The age
analysis of the birds caught show this. The Shorebirds 2020 surveys
at sites where there is no cannon netting show this, and the number
of flagged birds in these areas are very low. The birds caught show
a high site fidelity. But the people making the claims do not read
the papers, or the survey analysis. I guess the less you know, then
the more things that you can imagine might happen, even if they have
already been proven to be untrue.
9. Raptors. It is true that some birds in the past have been caught
by raptors as they are released. But the procedures have been
changed and there were none on last year's expedition. There are
lookouts posted for raptors. Birds are released in groups rather
than individually if there is any risk of raptors being around. It
is everyone's responsibility to lookout for raptors. I don't believe
that this is an issue any more.
Where do I learn about these things? By being a participant in the
expeditions. By being a member of the AWSG. It is sent by
email. It is published in Stilt and Tattler (published by the
AWSG). It is published in international journals. It is on the AWSG
web site. It is disseminated at shorebird conferences. Some of it
is communicated on the GFN web site. This information and much more
is available through cannon netting, and it does further the
conservation of these species.
There are vacancies for next year's expedition. You do not need to
be a member of the AWSG. It is not a holiday! There are early
starts, heat, humidity, lots of other tasks. But there is some time
for general birding. We look for a team of 23 to 25 people so we can
safely catch 250 to 300 birds in a catch. If we catch less then we
fully process each bird (band, flag, age, moult, weight, wing length,
etc). If we catch more then we reduce the amount of processing so
that the birds are released well before the three hour limit (at
least band, flag, age). There are tasks for people of all levels of
experience and fitness.
The people involved in cannon netting care more about these birds
than anyone, and do everything they can to promote the conservation
of these species. They put their time into it. It is grossly unfair
for them to be criticised.
_________________________________________________________________
Frank O'Connor Birding WA
http://birdingwa.iinet.net.au
Phone : (08) 9386 5694 Email :
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