I had prepared these messages before there was pressure to end the
thread, and I have decided to post them because I do not feel that they
are counter productive or inflammatory and I do wish to present my
entire argument for its own sake. How everyone takes deals with the
information will be up to them.
Admittedly, I have never done enough to test the effects of playback on
birds, but I did do a few experiments years ago that should interest
people.
I was doing breeding bird work in southern Ontario back in the Eighties,
and since I was returning to the same habitat over the course of a
breeding season here, I decided to try a few things to see what might
happen with playback. Hooded Warblers return here by early May and they
assume territory quite quickly so one has to be ready by the
third/fourth weeks of May to begin studying them. One of the first
things I noted was that, early on, they had a tendency to fly very high
into treetop canopies and return song. I found this unusual because I
was so used to them being a lower elevation species in behavior.
However, after breeding had been going on for several weeks, I did not
observe this again.
I was also interested to see if their response level changed after
having been played back to in a previous week. My first impression was
that this was the case. However, I had about 6 males on territory and I
decided to try a couple of them for the first time. Their responses were
much like the birds that had heard me before. I was beginning to get a
strong feeling that their reactions to playback had more to do with
their position in the breeding cycle and far less with my intrusions.
As the years have passed, I have become more convinced that this is the
primary criteria for all bird's responses to playback. And it is also a
primary reason why it is difficult to ascribe a birds reactions to
playback. Is he less reactive because I played to him last week, or
because things have changed back home on the ranch? I have mixed results
from playback on consecutive days, and I have done it so few times that
I will not hazard a guess as to this effect. Some people have described
a lack of reactivity, but I believe that this comment all too often
reflects my earlier statement about changes in the bird's cycle.
When I did inventory work in the Himalayas, I played back to birds that
had never encountered a birder, let alone playback. The weather in this
temperate zone had a lot to do with playback success, and it was very
pronounced. North face slopes were quiet with foraging flocks still in
evidence, while south facing slopes showed advanced vegetation and
advanced territorial behavior.
My warblers did well, and I observed no signs that I had contributed to
any failure or difficulty in their breeding process. I discovered that
playback in North America has limited value depending on the time of
year it is used. This contrasts sharply with what I experienced in the
tropics. And I will be up front about this. I have used playback
hundreds of times in the tropics. Because the birds are localized for
the entire year, their reactions are quite a bit different.
What do the birds do? This varies widely depending on species but the
important thing to note here is that their behavior is usually
consistent with their known habits. And, as I previously mentioned, it
depends on whether you are playing to a territorial bird, a young male,
a female, or a bird out of the breeding cycle. Many songbirds will come
straight at the sound, but I find this behavior to have more to do with
his position in the breeding cycle. Newly established territories elicit
a firmer response. Males with successful nests are more wary, as common
sense would dictate. Their reaction suggests " Do not give away the
location of one's nest ".
Females of some species will respond at this time also, and tropical
females, especially dimorphic species, can be quite reactive. For
example, female antshrikes will often approach like a male and call
back. Male antshrikes will approach similarly and use a contact call
that might be the same or slightly different from a female. An antpitta
may stay on a perch and call for quite a while after playback is ended,
but this is consistent with what they do with other antpittas.
In many cases, the bird will return in almost the same way that he
approached once his investigation is over. How long is this? Well, once
again it depends on the species. It may only take about 10-15 seconds
for the bird to be satisfied. On the other hand, a trogon might hit a
perch and sit for several minutes, calling softly. Most birds will hit a
perch that they are comfortable with and investigate from there.
It is important to note that how playback is done is critical here. I
believe strongly in the natural approach. A bird reacts best to its own
voice. Dialects differ, and pre-recorded tape is often not as good. One
needs to assess the sound quality of a situation and try to emulate it.
Some folks believe that the most effective way is to turn it up full
volume and let it roar. This has not yielded good results in my book,
and it does create a very unnatural soundscape as most recorded sounds
will contain hiss, handling noises, and other unpleasant things. I try
not to use anthropomorphisms in my analysis, but I can't imagine what a
bird senses when the " wren from hell " comes calling at his door.
The idea is that volume translates to proximity, but, when I have seen
it used, the reaction of the bird can be so swift that one misses
his/her best chance to see it. And birds do hear other things. Their
lives often depend on it, especially in feeding flocks where they listen
to the more vocal nuclear species with which they travel.
Repetition is another thing to pay attention to. Birds have their
rhythms, and I have found it more effective to emulate their rhythm
than to be impatient and try to " force " them in. That said, a common
result of playback reaction is for a bird to shorten his intervals and
increase his repetitions. I can often tell if playback was used on
someone's tape by this quality. That's why you will often see a
disclaimer on published products stating that intervals have been
shortened so as not to take up too much space on the recording.
The other effect is that one can often hear an increase in sharpness to
the same call that a bird used previously. This is clearly a reaction
from his heightened awareness and agitation. And this is where one needs
to pay attention. In order for me to assess my impact, I have watched
numerous birds reactions to other birds in their territory. This
knowledge is what can tell you whether or not a bird's reaction is
normal or abnormal to playback. They get very agitated with territorial
invasion, and sound merely leads them to the visual. Once contact is
made, actual scraps often ensue. This is probably the ultimate level of
agitation, but you can tell from playback where a bird is willing to go
if he visually finds the transgressor.
This information tells you when to turn off. If he doesn't see the
invader, he assumes his vocalizations settled the issue and he returns
to his normal vigilance. I am always amazed at how consistent the
direction and distance is to his return compared to his approach. When
playback is overused at this point, it could conceivably become
confusing to the bird.
I could go on and on here, but the big picture is this. Despite trying,
I have been unable to find much in the way of detrimental effect other
than the fact that they I did interrupt what a bird was doing at the
time of playback. The reason that all of us should talk about erring on
the side of caution is because it is so hard to attribute accurately the
effects of one's intrusion over any length of time. Nestings fail for
many reasons, and studies do show that various factors are at large.
Some birds abandon nests for no reason we can see. I can only say that,
if we were able to find a nest, maybe it was too easy and a predator
did, also. But I want to make it clear that I emphasize playback done
sparingly and as naturally as possible. If one knows the habits of a
bird, it is easy to see when abuse could occur. In my experience, it
probably wouldn't do any long lasting harm, but why would you want to
chance it?
I can imagine the reactions of some folks at this time, but I have only
one more post to go. That will be a discussion about recreational
birding in places like North America and where I feel playback should
and should not be used.
Scott Connop
________________________________________________________________________
________________________________________________________________________
|