Don Baccus wrote:

> This is why study of known-sex birds is important, how else do you
> establish the parameters for distinguishing sex?

When banders in northern Scotland were working on Snow Buntings, it
took about 3 years of data to pull together all the criteria
necessary to be able to reliably sex birds. The first 60% of birds
were easy, the remaining fraction took a considerable amount of work
through retrapping birds of known age etc, to work out the plumage
differences !!!

If it was difficult for an obvious bird, I'm sure it's just as bad
for chestnut-collared longspur, perhaps worse. Catching this bird
may not tell us anything more than we already know !!!

Chris Hill's friend wrote:

> I see...science. And where were you planning to publish the
> result?

Exactly; there is probably no real way to publish the information.
The measurements might be useful, but given there is variation in
measurements taken by different banders* so pooling the data into
other studies would not be worthwhile.

* measurements are slightly subjective, in the sense that there are
variations in the way each person takes a particular measurement.
The The variation in measurements can be as much as 2-3mm for
winglengths or 0.1-0.2mm for bill length. This variation is large
enough to ensure that direct comparison between studies is not
really possible.

Banders working together soon eliminate this human source of error.
Shorebird banders in Europe regularly work together so there is
little regional or international variation in measurements taken
enabling the data to be pooled or used in comparative studies.

Stuart
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Stuart MacKay - powered by NeXTSTEP

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