NSF PR 96-19 - May 3, 1996
Media contact: |
Cheryl Dybas |
(703) 306-1070 |
Program contact: |
Randy Nelson |
(703) 306-1419 |
This material is available primarily for archival purposes. Telephone
numbers or other contact information may be out of date; please see current
contact information at media
contacts.
Never the Same Song Twice from Song
If song sparrows were humans, they would be jazz singers....and
folk singers....and pop singers, says Steve Nowicki,
a National Science Foundation (NSF) grantee who is
a zoologist at Duke University.
"Many birds sing songs repeatedly, but with song sparrows,
it's not repetition -- it's variation. These birds
rarely sing the same thing twice."
Song sparrows learn as chicks to improvise on old
standards. Not only does this ability set them apart
from other birds, it calls into question basic assumptions
about learning, evolution, and animal communication.
"According to neurobiological theory, birds keep songs
in a sort of memory template," says Randy Nelson,
director of NSF's animal behavior program. "Songs
stored there can be reeled off at the proper moment.
More complicated songs presumably use more complicated
templates."
Yet nothing in the theory accounts for song sparrows'
ability to improvise -- or their motivations. "As
an evolutionary biologist, I find it interesting because
the different things the birds say don't seem to mean
anything different," says Nowicki. "So what's the
point of variation?"
The biologist is trying to find out. Nowicki documented
song sparrows' variations by making sound recordings
in the Pennsylvania woods and observing how birds
behaved as they sang and listened to one another's
songs. "They may be doing it to prevent habituation,"
Nowicki suggests. Like a familiar song with unexpected
lyrics ("Row, Row, Row Your Canoe," for example instead
of "Row, Row, Row your Boat"), a bird song may attract
more attention when it is varied.
Another theory has to do with attracting a mate. Darwin
attributed exaggerated male traits, such as peacocks'
tails, to their ability to attract females. With more
varied songs, song sparrows may be more successful
in wooing mates. To test this theory, Nowicki plans
to play various males' recordings to females. A female
signifies when a song has struck a chord by fluffing
up her feathers and preparing to mate. If the theory
is correct, this behavior should occur more often
with more varied songs.
Nowicki is also exploring other explanations, such
as territorial defense, as well as investigating the
neurobiological mechanisms by which song sparrows
learn to sing their varied songs.
|