Jack Walters wrote:
> I have never heard of banders recording deaths that they cause.
You are hereby notified that the Goshutes Raptor Project tracks its
mortalities, which over the last few years have been roughly in the
range of one mortality per 3,000 captures. We study each mortality in
detail in an effort to learn what went wrong and how to prevent a
recurrance. As a result of incorporating such knowledge in our training
of banders, we have been very successful in reducing our mortality rate,
which was about one per 750 captures a decade ago.
I would estimate that about 3/4 of what we know about migratory
movements of sharp-shinned hawks, Cooper's hawks, red-tailed hawks, and
American kestrels in the intermountain west comes from this single project.
For instance before banding in the Goshutes commenced it was unclear as
to where Cooper's hawks from your region spent the winter. We now know
that most spend the winter in the Sierra Madre Occidental in the Mexican
provinces of Sinaloa and Sonora. This information not only satisifies
the curiousity of researchers but is important for those who are
interested in the conservation of this species.
We've also established that Cooper's hawks can live at least to the age
of 12 in the wild.
Likewise the information gleaned for other species.
We are using satellite transmitters on goshawks, red-tails and golden
eagles. Telemetry provides us vastly more information than a simple
band, though these birds are banded as well.
If or when satellite transmitters become small enough to be used on
Cooper's hawks or even sharpshinned hawks, and cheaper (total costs per
bird are about $2,000 now, along with the transmitter there's costs
associated with getting the data), our focus will shift almost
exclusively towards telemetry. Telemetry yields so much information
that we'd only need to capture a tiny fraction of the birds we capture
for banding today.
But until that happens we're stuck with good old luddite bird banding
for smaller species, and due to the low return rate in the relatively
scarcely populated intermountain west and the remoteness of forested
ranges in Mexico we'll continue to put bands on large numbers of birds.
(for the curious our return rates are in the neighborhood of 1%, while
band returns for accipiters in the more heavily populated and roaded
eastern US are in the neighborhood of 5%)
In recent years the USF&W has worked to reduce the number of "backyard
banders", people who are more hobbyist than researcher. They do a good
job with their records IMO, I know they catch at least one error in our
banding data almost every year.
http://donb.photo.net, http://birdnotes.net, http://openacs.org