In reply to Marilyn Davis's posting in which she argued that the decline in
Curlew Sandpiper numbers is caused by leg-flagging:
1. Curlew Sandpiper numbers have dropped alarmingly in southern Australia,
and counts are now about a third of what they were in the early 1980's. The
Australian population was about 200,000 in the early 1980's, so one could
perhaps argue that around 140,000 have 'gone missing'. About 40,000 Curlew
Sandpipers have been banded in Australia over the past 50 years, and fewer
than half of these have been leg-flagged. The maths isn't complicated - it
is impossible that leg-flagging could account for a population decline of
this magnitude.
2. The decline in Curlew Sandpipers is widespread, and has occurred in many
places (e.g the Coorong in South Australia) where no intensive banding
projects have occurred.
3. It is simply not true that most leg-flagged birds 'simply disappear' - if
that were the case, there would be no point in flagging them. Analyses of
survival rates of Curlew Sandpipers are in progress, and although they are
not yet complete it is already clear that the chances of a banded Curlew
Sandpiper surviving from one year to the next are between 75 and 85%. No
difference can be found between the survival rates of birds that have been
leg-flagged, and that of birds that have simply been banded. The rather high
survival rate of Curlew Sandpipers is comparable with that found in all
other studies of wader survival, whether they be based on colour-banding or
plain banding studies. Waders are long-lived birds.
4. The most commonly banded and flagged shorebird in southern Australia is
the Red-necked Stint. Red-necked Stint numbers in southern Australia have
INCREASED over the past 20 years while banding activity has been highest.
5. The assertion that habitat destruction in the East Asian-Australasian
Flyway is not the main cause of Curlew Sandpiper decline is baseless. Curlew
Sandpiper migration routes are still incredibly mysterious and there is a
huge shortfall (larger than for most other shorebird species) between the
numbers seen in Australia during the non-breeding period, and the number
seen in staging areas during migration. It is not known where the majority
of Curlew Sandpipers stage while migrating, so there is no way of telling
whether these vital habitats are secure. Given the rate of wetland
reclamation in Eastern Asia, habitat loss must be a candidate as a cause of
the Curlew Sandpiper decline.
6. It is likely that low breeding success in recent years has also been an
important factor in the decline of Curlew Sandpipers. Banding has shown that
they have had a succession of rotten breeding years (in contrast, Red-necked
Stints have had a series of good years). The last breeding season was the
best that Curlew Sandpipers have had in many years, but we do not yet know
what effect this has had on the population.
Other errors in the Marilyn Davis posting have been pointed out ably by
Frank O'Connor. At best the Marilyn Davis posting was ill-informed and
lazy - a simple literature search or a couple of polite phone calls would
have been sufficient to get the facts right. At worst the posting was
dangerous. The decline of Curlew Sandpipers is worrying, and the problem
will not go away if we simply stop leg-flagging. We need to find the causes
of the decline if we are to do something about it, and the chances that this
can be achieved without a banding and flagging program are very slim indeed.
Danny Rogers, Ken Rogers
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
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