Dear Ian,
The alternative hypothesis is that the banded birds congregate at the site you
mention prior to leaving Australia, but disperse elsewhere when first returning
to the country. This would seem as parsimonious as the assumption that every
single one has perished.
The study you describe is exactly what is needed, although a third marking
technique (such as RFID tags used to microchip pets) would also allow
assessment of the impact of different experimental groups: no external band,
metal leg band only, leg flag only, leg and metal flag and so forth. It would
require a long-term study (ie several seasons commensurate with a PhD timeframe
perhaps?) with large numbers of birds being captured and marked over several
sites. This would cost significant funds and many hours labour, however would
be very useful in settling the debate based on evidence. Clearly there is
precious little data one way or the other, with much assumption on all sides.
Simply observing a leg flag and labelling it as a killer is unacceptable,
equally so is releasing a bird with leg flags and assuming that all will be
well.
As I've said before, either someone needs to undertake a study similar to what
you describe, or we stop talking about this, as there is not enough data to
make informed decisions at present. I do not have the funds, nor the time to
undertake the study personally. However, I would be more than happy to assist
anyone interested in undertaking by helping to oversee such a study with the
statistical analyses, confirming valid scientific methods and, if there is real
interest from skilled banders, attempting to prepare grants to obtain funding
to go ahead and do this.
There is clearly no point continuing to petition current banders to assess
their practises, even if they do, the comments on this forum clearly
demonstrate that their data is labelled as biased a priori by critics of their
techniques. Given this response, we cannot be surprised or disappointed that
primary research goals are not sacrificed to collect data that will be
ultimately ridiculed.
To qualify, I do not have any great connection with current cannon netting
folk, though have assisted some with cannon netting 2-3 times in the past,
ca.10 years ago.
Cheers,
Paul
On 06/08/2011, at 8:51 AM, Ian May wrote:
> Hello all
>
> In light of the current discussion about wader leg flagging, I have decided
> to post the following so that others can consider for themselves, if leg
> flagging is killing our waders.
>
> On 2nd July 2011, a visit to a local mudflat in northern St Vincent's Gulf,
> South Australia, produced 600+ wintering migratory waders. There were at
> least 53 Curlew Sandpipers, 23 Bar-tailed Godwit, 8 Red Knots, 3 Greenshank,
> 1 Mongolian Sandplover, and 500+ Red-necked Stint scattered across about
> 20 Ha of prime habitat. There were also 40+ Double-banded Plover and 15+
> Red-capped Plover.
>
> Not one of these birds was plagued with a leg flag. Is this good or is it
> bad? Of concern to me was that despite the large numbers of leg flagged
> waders in the area just prior to their migration (March/April), what happened
> to the many flagged birds that were here only three months ago?
>
> People who speak against leg flagging of waders on this forum are frequently
> advised, “Unless there is something new, stop now”.
>
> So here is something new.
>
> Not much flagging if any is done in the area of St Vincent’s Gulf, SA.
> Often about 3% of the thousands of waders that congregate here are seen with
> shiny new looking flags just prior to migration (Feb, March). However when
> birds first return (August and early September), rarely does one see a
> flagged bird among them. This indicates that most of the flagged birds
> previously seen have disappeared, probably died during their post flagging
> migration. Occasionally I see a bird with an older faded flag but this is
> rare.
>
> Considering the observations have been repeated over many years and that "Leg
> Flaggers" are targeting some of our most vulnerable species, some of which
> are possibly declining because of leg flagging impacts, about two years ago I
> discussed my concerns with one of the flagging organisers.
>
> The conversation was civil and part of it went like this!
>
> I said “there appears to be little or no research into discovering the likely
> negative impacts of leg flagging on small waders (Great Knot and smaller).”.
>
> He said “Some effort would be made to analyse previous retrap data in future.
>
> I suggested “Perhaps some of the future trappings of say, Red-necked Stints
> should not be flagged but instead be fitted with 1 only traditional small
> metal band so that survival comparisons can be made with multiple leg flagged
> birds”
>
> He said “No No, this would not be necessary as current data would show any
> variation”
>
> I said “Before leg flagging was introduced, when there was little wader
> banding activity compared to today, it was not uncommon to see returning
> migrating waders in southern Australia wearing a single worn metal band
> indicating their survival post migration. But now, despite the hundreds of
> pre migrating freshly flagged birds that we see at Price each year, rarely
> does one see any returning with flags in the following season. (This
> indicates to me that some numbers of waders do survive after one leg metal
> banding but few return after leg flagging).
>
> I said. Why not consider fitting to say half of your trapped birds, just one
> metal band and no leg flag, so that impact comparisons of both techniques can
> be made by any field observer. It would soon become obvious if we observe a
> higher proportion of metal banded birds returning from migration, that the
> flagged birds are dying because of leg flags”
>
> He said “This would mess up our statistics and is not necessary. We can
> get the same results by analysing existing data”
>
> I said "If there is no problem, what happens to all the leg flagged
> individuals that I see here at Price just prior to migration? The flagged
> birds just do not come back!
>
> He said “These birds are notoriously site unfaithful, mostly returning to
> the Gulf of Carpentaria where very few observers see them”.
>
> (But if anyone cares to read the literature, the Global Flyway network states
> when discussing retrap results, "thankfully, flagged birds are notoriously
> site faithful")
>
> Summary
>
> Field observation of wintering waders indicates that leg most of the pre
> migration flagged birds are either dying/disappearing/not coming back.
>
> The only reasonable solution is to call for a moratorium on leg flagging in
> Australia for at least a period of three years. Such a moratorium would
> provide circumstances for independent parties to observe and evaluate
> leg-flagging impacts through normal field observation techniques. In seasons
> following a moratorium, Australian flagged waders relocated would clearly
> indicate the birds that are surviving migration and this result would
> finally, prove that leg flagging is of no harm or, is killing our birds.
>
> The results would either confirm or put to rest, the concerns of many who
> believe based on years of field experience, that leg flagging small waders is
> a destructive practice.
>
> Regards
>
> Ian May
> PO Box 110
> St Helens, Tasmania
>
> 0428337956
>
>
>
> (To see a flagged bird, see Page 1 of
> http://www.globalflywaynetwork.com.au/reports/GFN-Report-NW-Australia-2009.pdf
> )
>
>
>
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr Paul G. McDonald
Lecturer
Zoology, School of Environmental and Rural Sciences
University of New England
Armidale NSW 2351
Australia
Ph: +612 6773 3317 Fax: +612 6773 3814
Publication list: http://publicationslist.org/paul.mcdonald
Thompson ISI Researcher ID: http://www.researcherid.com/rid/A-5928-2010
Web: http://www.une.edu.au/staff/pmcdon21.php
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