Hi All,
I've already chipped in here, so I probably shouldn't say too much
more. And thanks to Andrew Taylor for finding the summary from Neoorn,
it's a good review. But it seems that the best argument, and the one
that would seem to have the most scientific consideration, would be
the "excessive spent energy" one.
But how much energy exactly, quantified, is a bird expending when it
reacts to tape, pishing, or mobbing? And how much does that compare to
the energy the bird has available to expend on such behaviors?
Those are very hard questions to answer well, but that's where the
answer lies. But if you watch birds do perfectly normal, every day
things without playing tape, pishing and mimicking owls, and then
watch their responses to those stimuli, you can get an idea.
I watch a bird pursue a small insect in an amazing burst of energy,
chasing it for a full 30 seconds in nonstop flight. I see a
territorial bird go after an intruder for 5 minutes without pause. I
watch a group of birds mob a cat, snake or owl for 10 minutes without
pause. And it would surprise me if any amount of tape playing,
pishing, etc. I have ever done (and I've done quite a bit) measures up
to the normal, daily energy expenditures that I witness. I think if a
bird is short on energy, they will spend it looking for food rather
than responding. In fact, I frequently watch birds responding to
pishing and owl imitations forage along the way, while chipping and
coming in for close views.
I might mention that though I have years of tape playing experience,
and I'm pretty convinced it doesn't have much of an effect on birds,
it's not something I recommend very highly. Often birds don't respond,
so you've wasted time you could have spent looking for other birds.
It's distracting and noisy (few recordings really have no background
noise). And the response you get is uninteresting and sometimes even
makes the bird harder to see than if you had just waited a bit. A bird
responding territorially has to be concerned about physical contact
with the supposed intruder as well as aware of the presence of
predators. So the response is usually of a very wary bird, moving
fast, reacting to your smallest movements by fleeing, and going into
what a friend has called "satellite mode" – encircling you with
frustrating speed. On the other hand, there are some species that are
best (and sometimes only) seen with smart use of playback.
I suspect the actual effect varies from species to species, and I hope
that a controlled study would include birds from several different
groups. Some birds will abandon the nest with any sort of disturbance
(I've been told that Swainson's Hawk is this way). With others, you
can barge in for 10 minutes, take the eggs out of the nest, replace a
parasite-ridden nest with one saved from last year, replace the eggs,
and see no problem at all.
Good Birding,
Rich
---
Rich Hoyer
Tucson, Arizona
Senior Leader for WINGS
http://wingsbirds.com
---
On Sep 15, 2008, at 4:51 PM, Douglas Carver wrote:
I have taken courses with two different ornithologists at the
Smithsonian
Institution. Both cautioned against using playbacks, except in rare
instances, and even then using them sparingly (one had a rule of
thumb that
if the bird did not appear after the second playing of the call or
song, he
would not try a third time). While neither had hard empirical data
(or at
least, no data they shared with the class), they both said that a bird
responding to a call is expending energy needlessly, which puts
unnecessary
stress on the bird. The bird's well-being is more important than our
twitch.
Cheers,
Douglas Carver
Albuquerque, NM
USA
==============================www.birding-aus.org
birding-aus.blogspot.com
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