In this posting, I would like to share my observations on the use of
playback, mostly short-term. I have not scientifically approached the
subject in all aspects, but I have experimented a bit over the years,
particularly to observe any long-term effects.
I first saw playback used in the early eighties on a neotropical tour
that I participated on. Its productive use on shy forest birds was
immediately striking, and I became aware from the start that tropical
birding would require a different approach from that I had learned back
in Canada. I did not use playback in North America until I had actually
spent a couple of years doing it abroad (and it has always been sparing
here, more on this later). The need was simply not apparent here. I had
learned my visual birds well, although I found that my knowledge of
sound was weak in comparison, and this is the case with many birders.
Playback does not always work, and the reasons for this underscore the
reason for understanding one's subjects to a reasonable degree before
using it. I had a number of encounters where the playback of one song
elicited an immediate response. Depending on the bird, though, the
nature of of its response could vary, and it took me a number of years
before I could really assess why.
Some birds would call back immediately. Others would approach first and
then call. Some would approach and hardly make a sound. Some birds would
call back but not approach. Many picked a favoured perch and stayed put.
The first trick I learned was that, the moment I played back, I needed
to watch very closely because the approach of most birds was usually
with a measure of stealth but often immediate. I learned that many birds
made their best approach on the first call. There were times when I did
not realize that my bird was right there and no extra playback was
required.
However, with certain familes, such as antbirds, it was often a
different story. A typical response would be for the bird to sing a
little and then take its sweet time moving in. I did not see an antpitta
until my second trip into the neotropics, and it took about 10 minutes
before I got a look. The bird picked a low perch on a rotting log, and
only by getting low did I pick up the movement of its throat and then
actually see its outline. Many antpittas have long, quavering songs and
their throats actually expand and vibrate when they sing.
What I learned over the years is that these birds have their own
response to other singers in their territories and I needed to learn
what this was before I could use playback effectively and with
discretion. I realized quickly that, in tropical birding, territories
were often within audio range of each other, and these birds were
constantly reacting to each other. The critical element was proximity.
The birds knew their mapped out territories but there was always
incursion, and their reactions varied depending on the degree of
incursion. This became one of my first guidelines in using playback. If
a bird was out of territory, one's chances of drawing it in were poor.
It depended on the species, size of territory, and one very important
criteria - seasonality and position in the breeding cycle.
This is the main difference between birds here and there. Temperate zone
species have a short, sharply delineated breeding season whereas
tropical species are more drawn out and are effected by wet-dry cycles
in weather. Also, tropical species will be vocal to some degree
throughout the year, whereas we see song here curtail quickly and and
become non-existent in migration. I believe strongly that, because
migration is such a traumatic and vulnerable time, birds have adapted to
be quiet. Accipiter (predatory hawks for the non-birders) migration is
timed to take advantage of songbird migration patterns and abundance,
and the need for quiet is paramount.
However, many of our migrants perk up on the wintering ground. For
example, Yellow-bellied Flycatchers are very vocal with call notes in
Costa Rica, and Wilson's Warblers are constantly chipping away in
Central America. Swainson's Thrush are often heard in South America
uttering what we call sub-song, a variant of what we will hear when they
return.
The bottom line here is that the effectiveness of playback is strongly
determined by the phase of breeding by a territorial bird. Being in the
right place at the right time means that it will work well. Being out of
season means that a lot of folks could be blaring sound at birds that
are only marginally interested. Also, certain species are far more
reactive than others. It makes no sense to shower sound on a species
that does not react to others of its own that well. Lek breeding species
such as some cotingas and manakins are used to having competition right
beside them. Getting close to the lek is a better way to see them and
they are not interested in leaving the lek.
There is more to this but I know that some folks probably feel inundated
at this point so I will save it for another post on long-term comments
and playback in North America
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