At 04:15 PM 10/25/2005, you wrote:
>Hi Gerald,
>
>Here in the Neotropics bird surveys are usually not regular events that ar=
e
>repeated in the same areas, but often quick visits to areas that have neve=
r
>even been visited before.
>
>Most resident territorial are year-round territorial, and from repeated -
>though always judicious - playback in areas that are not heavily visited
>(which would be a different story) I have the impression I have never
>chased a bird of its territory.
>
>I think that other than the quality of the playback also the volume plays =
a
>role. If the playback volume is low the territory owner will often respond
>better, perhaps having the impression he's dealing with just a weak
>intruder. I can see how birds get driven off their territory through
>unjudicious, loud and too-often repeated playback.
>
>Best regards, Paul
Paul is exactly right. I spent the summer of 1958 in British Columbia on
Cornell-funded research, playing songs of eastern Empidonax to avian
suspects in varying habitats -- an extension of the PhD thesis work on
Alder flycatchers of my colleague Robert Carrington Stein. Speaking of old=
equipment - it was a Magnemite wind-up 78 RPM "recorder" (with the huge
wheel capstan??) and a TUBE battery amplifier - we were lucky to get 1 watt=
of output to the speaker! I guess these days one would say: Typical of you=
Yanks! Imposing your "American" sounds on our poor Canadian birds! Shame."=
and wouldn't be far wrong . . .;^)
The main thing that emerges immediately from such research from the get-go=
is two general aspects:
1. play a song more than once or twice and you may never see the male bird=
whose territory you have invaded. At least not for many minutes. What
response you are getting happens immediately, and if you think you'll try
one more playback after two songs you are kidding yourself - you missed
seeing whatever the owner actually did - flew by, went into hiding,
etc. More plays just radically cause the motivation to get worse, it
usually does not make the relevant behavior more VISIBLE.
2. play it at the wrong volume and it really messes things up. Too loud
and, practically speaking, the poor thing goes into what I call "tilt!" Too=
soft and the bird often flies swiftly overhead, in search of the "distant
rival". On the second play (again too softly), the subject typically gets=
visibly confused because in addition to being puny and pusillanimous, the
rival has now switched boundary sides - a totally biologically improbable
event for which evolution has not prepared your bird one iota. Sound level=
meters are almost useless for establishing the "correct" volume. I have
never figured that one out. With a group like Empidonax (we were using
pre-recorded songs from E. trailii, E. alnorum, E. minimus, E. virescens,
and E. flaviventris and comparing responses from territorial males in shrub=
swamps to see if the two "Alders" behaved in the west as they did in the
east). They did.), we set the volume by listening from a distance until it=
sounded as natural as possible and then marking the control knobs in
ink. Amplifier battery life (remember "A" 6v and "B" 90v?) was not helpful=
in this regard.
What is also amazing to me to this day is that a tiny bird can clearly
orient correctly to a sound source in mid-flight. This happens often, that=
as the second call is emerging from the speaker, the bird happens past
awing. Not only do those "microphones" work at thirty miles per hour of
wind, they provide directional info accurate to within a few degrees. We
were using a painted model, made by the indefatigable Bill Dilger (of
playback Hylocichlid fame) and it was difficult to make the bird orient to=
the model rather than the nearby speaker itself.
But I do ramble on. . .
-- best regards, Marty Michener
MIST Software Assoc. Inc., P. O. Box 269, Hollis, NH 03049
http://www.enjoybirds.com/
Don't blame me, I vote in New Hampshire!
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