Biology Reference
In-Depth Information
Per unit weight, Winter Wrens have ten times the sound power of a crowing rooster,
and birds in the Eastern population sing a good 16 notes per second — an impressive
output that is not only exceeded but more than doubled by Western birds, which sing 36
notes per second! Their rapid heartbeat, respiratory rate, and metabolic rate don't explain
the output, since larger and smaller birds don't match this! But what is even more amaz-
ing is that these birds not only produce the sounds but react to tiny parts of the songs,
so their ears and brain can resolve in real time individual notes that we cannot without
replaying the songs at slow speed.
Q Why are bird calls so varied? Cardinal and Mourning Dove calls are so different
from each other, for example. Is there something in their physical makeup that
makes the sounds distinct?
A
Yes.Thesizeofthebirdandlengthofthetracheaandbronchialtubesimpactthesound
quality and frequency, and produce sounds in their syrinx, which is far more complex
thanourhumanlarynx.Althoughourlarynxisasimpleinstrument,madeofamusclethat
spans the trachea and can be controlled to make varying sounds, human voices are still
so variable that most of us can recognize dozens, and sometimes hundreds, of individual
people by their voice.
Thesyrinxislocated wherethetrachea branches intothebronchial tubesand,depend-
ing on the species, may have a variety of muscles arranged within this more complicated
framework. When a group of people sing together, we make up a chorus. When birds do,
it's more like a whole symphony orchestra.
NAME THAT TUNE
Describing bird sounds can be tricky.
For example, I once received this question:
“Could you tell me what bird is most often the first to sing in the morning, and sings all
day. I hear it most of the year except in winter.”
Robins are usually among the very first birds to pipe in with the dawn chorus, so I
sent him to a Web page with the robin song and told him that if this wasn't it, to please
try to describe how the sound of his bird was different. He wrote back, “This bird has
a two-sound cadence — a short sound and a very long ending that runs for maybe two
seconds. I normally hear this bird near water or marshes.” I still didn't have a sense of
its tonal quality, so I asked if it sounded buzzy like a Savannah Sparrow, with another
link. He responded, “No, it's more melodic — a long pitch sound like the bird is saying
hel-lowwwwwwwwwwwwwwww.
”
Then it hit me. He was describing a White-throated Sparrow. When I sent him a link
to that sound, he was ecstatic. Detective work can be ever so rewarding.
