Hi all,
There are many subtle effects of vocalisation playbacks on bird
behaviour. Energy wastage as a direct result of playback is probably
not very important, as most birds aren't operating at the point where
a few minutes wasted time is critical to daily maintenance. However,
only a small amount of playback can have a significant and long-
lasting effect on individuals. See for example:
Mennill, D. J., Ratcliffe, L. & Boag, P. T. 2002 Female eavesdropping
on male song contests in songbirds. Science 296, 873.
For those without access to this article, it essentially showed that
females seek extra-pair copulations with adjacent males following
simulated playback defeats of their putative partner. Typically
singing birds are engaging in song contests, with the 'winner' often
able to be judged from other birds overhearing the interaction
(labelled 'eavesdropping'). For example, winners might overlap their
calls with the loser, match the loser in pitch etc. The actual
mechanism whereby contests are decided is likely to be subtly
different for each species. The point is that with only a very short
playback period (something like 6 min I think from memory in this
article), the authors triggered females to drastically change their
reproductive behaviour.
Likewise, it has been shown in many species that other males also
eavesdrop on these interactions, and the 'loser' may be prone to more
intrusions from adjacent males, as his quality may be inferred to be
lower than it actually is following an experimental defeat. Thus, by
continually playing calls in the one territory, I suspect birders are
effectively simulating the resident bird 'losing' to the tape/mp3
player that it fails to evict from its territory. The energy lost
directly is unlikely to be important as I said, but extrapolating from
other species that resident male may lose paternity of its clutch and
also have to spend more energy defending its territory in the coming
days after the birders have left. I'm not aware of any papers that
test this directly, and this is unlikely to lead to any conservation
issues. However, it does raise ethical concerns, as the results from
the playback may continue well beyond the point birders have left the
area.
That ends my two cents worth,
Paul
On 16/09/2008, at 6:25 PM, L&L Knight wrote:
There are very few, if any species, in Australia that you can only
see by using a tape to draw them out. It's more a case of whether
you want to see a species quickly / conveniently - as is the case
for birding guides finding target species for clients.
Regards, Laurie.
On 16/09/2008, at 1:25 PM, Alistair McKeough wrote:
I'd be interested to know how reliant people are on it. I know I've
seen
birds I wouldn't have without using tapes (eg Lewin's Rail).
Anyone with 500 species that's never used tapes? How about 600? 700?
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Dr. Paul G. McDonald
Centre for the Integrative Study of Animal Behaviour
Macquarie University
Sydney, NSW 2109
Australia
Ph: +612 9850 9232 Fax: +612 9850 9231
http://galliform.bhs.mq.edu.au/~paul/
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