Chickadees: Cultural evolution through social learning
"Social learning often results in local behavior
traditions" and "maintenance of traditions involves social learning combined
with selective processes." Mark's observation of the unstated obvious: All maintenance
of tradition due to social learning. Tradition = social learning.
In terms of their pitch and frequency modulation
measurements, they didn't start out with much to work with. Prompts me to present
an analogous comparison- paintings analyzed by photographs taken through a couple
of layers of rough cotton gauze.
I wonder if Chickadees find the micro pitches (those
high frequencies beyond the researcher's measuring devices capabilities) very
important. An experimental playback of their recordings to measure Chickadee
response and territoriality would make the study more compelling for me.
Their graphs with arrows enhance a discussion of
how the birds changed pitch after two hundred songs, but to me those graphs
trace how the birds vary their song every 50 to 100 songs, possibly to give
their tissues a break and avoid chronic fatigue syndrome.
They determined that "Songs containing pitch ratios
altered by 0.12 or more from the population average are not as effective at
eliciting a territorial response."
Chickadees tend to ignore the idiosyncratic or eccentric.
So often do human societies; but some societies
fear them, while others respect and value them.
From Conclusion: " social pressures exist in black-capped
chickadees that favor individual birds that sound similar to other conspecifics."
In other words, Chickadee society favors traditional singers, and that perhaps
"pressures attenuated" (lessened tradition, allowed for more variation in song)
around Fort. Collins due to "less population mixing" and/or a sparse population
when originally colonized. They wonder aloud whether this original adventurous
group of birds enjoyed a "relaxed social selection regime." I particularly like
the phrase that suggested "selection for song conformity was overwhelmed by
a higher cultural mutation rate in Fort Collins."
In other words, the Old World Order fell to the
New Traditionalists, the "Neocons" or new conservative Chickadee.
"The repertoire also provides an opportunity to
examine how vocal signal innovations originate and the mechanisms of cultural
evolution, which may provide evolutionary principles that generalize to other
species that acquire socially learned behavioural traditions."
As a subtext, they hope their research will help
discover the mechanisms of why humans learn new stuff and believe it traditional,
i.e. believe this is the way things have always been.
South African diamond merchants invented the wedding
ring tradition, for obvious reasons.
_______________________________________________
Technical section for real geeks:
The included Oscillograms and Spectrograms make
it obvious that when these researchers describe a song's pitch "more stereotyped"
they mean less pitch variation, more monotone. They recorded Chickadees song
pitches that ranged from 2.5 kHz to 3.8 on the Chick-a-Fee-Bee song; a full
octave musical scale would range from 2.5 kHz to 5 kHz. Probably what musicians
call a 5th or a 6th.
After all the brag on their funded Sony and Sunnheiser
equipment, they describe spectrographs made with Syrinx software at 22.05 kHz
sample rates with a 16 bit accuracy.
I feel my leg pulled. A 22.05 kHz sample rate means
only frequencies below 10 kHz show up, about the resolution of a bad telephone
connection, and 16 bit "accuracy" most probably refers to the amplitude of the
oscillogram waveform- in other words, simple loudness, not "accuracy". Although
each loudness line every 22 thousandth of a second does reveal cumulative frequencies
up to 10 kHz.
When I read about their use of an onscreen cursor
to measure the ratio of Fee to bee pitches, "which allowed a pitch resolution
of 4 Hz", I wonder how four cycles per second helps them measure anything but
the compression-wave woofers in their pickup's barrio blaster sound system.
Probably a mistype of 4 kHz, within the 10 kHz limit of their sample rate. Probably
a technical way to say they got an average pitch.
They admit Temporal variables varied more than pitch
variables; i.e. timing and phrasing changed more than pitch, but they analyzed
pitch and frequency variation instead. Easier to quantify? .
With CD-quality resolution (44 kHz) and hopefully
even better (a bird's tiny vocal chords must produce very high frequencies),
and software that might trace the resultant oscillograms and find much finer
frequency averages and deviations, an emotional "tone" might show itself; for
example, subtle stridencies of high frequencies or timing (phrasing) that communicate
when a bird feels threatened or more territorial. But that's a different study…
_______________________________________
Chickadee "The Whistled Fee-Bee song of the Black-capped
Chickadee" pronounced out of the side of the mouth of W. C. Fields, who as a
young man traveled the civilized world as a juggler, eventually found success
in Hollywood as a fat comedian-actor, famous for drunkenness and a hatred of
animals and children.
"Implications for cultural evolution through social
learning"
Song repertoire evolution and acoustic divergence
in a population of black-capped chickadees, Poecile atricapillus DAVID E. GAMMON
& MYRON C. BAKER Department of Biology, Colorado State University (Received
6 March 2003; initial acceptance 29 May 2003; ?nal acceptance 22 October 2003;
MS. number: A9568)
Vocal learning documented in nearly all evaluated
songbirds and other birds and four mammals, most show geographic variation.
Some changes due to imperfect (social) learning.
Mark's observation: All maintenance of tradition
due to social learning.
Chickadees seem to return to territories about 5
meters round, 10 meters from each other.
None of the 30 songs recorded in 2001 outside of
Fort Collins contained introductory notes.
The obvious acoustic differences distinguishing
the Fort Collins song types were the presence of chick-a and fa syllables, and
the consistent amplitude break in the fee syllable of chick-a-fee-bees (Fig.
1).
Songs in Fort Collins clustered into three groups
according to pitch as reported above, the songs from all other study sites clustered
into a single group.
Three Fort Collins song types (chick-a-fee-bee,
fa-fee-bee, or fee-bee-3). Of the 10 birds, eight sang all three song types,
and two sang just chick-afee- bee and fa-fee-bee. Generally, chick-a-fee-bee
was the most common song type within individuals (20-62% of all songs during
an individual's dawn singing bout) followed by fa-fee-bee (7-54%) and then fee-bee-3
(7- 33%). For the eight birds producing all three song types, the average usage
frequencies were: chick-a-fee-bee: 45%, fa-fee-bee: 36%, fee-bee-3: 19%. Countersinging
and occasional song-type matching between neighbouring birds occurred for each
of the three song types (see below).Diversity of SpeciesByFiltration
I read (tried to read) this huge book by immensely
famous biologist and I can't remember for sure the title nor the author but
the concept that stayed with me went like this:
A mammal needs a continent for enough isolation
to evolve a new species, but an insect perhaps just a tree…
Or a particular species of tree. So this slight
change in birdsong my represent something that between six or one hundred or
a thousand generations becomes genetic, if the "artificial selection" of female
Chickadee choice favors the new tradition, and that it may be coded into genes.
So far, the gals prefer the old song.
Which starts up the controversy of whether genes
"learn" from learned behavior, i.e. if some feedback of proteins or enzymes
could influence the gametes, or do all changes come from random mutation filtered
by "selection" whether through environmental lethality or female choice.
I think the term filtration works better; it helps
me understand "selection" as impartial and removes the taint of a purpose, or
goal.
