The skylark could be going up in the world. The crow
has something to crow about. Scientists could be about to think again about the
little grey cells of the grey goose. From now on, a bird's brain may no longer
be classed as birdbrained.Mammals have complex brains, including a neocortex for
learning tricks and nerve cells called basal ganglia which control instinctive
behaviour.Birds, until now, have been thought to have only basal ganglia. But
the avian nomenclature consortium - an international team of 29 neuroscientists
led by Erich Jarvis of Duke University medical centre in North Carolina - argue
today in Nature Reviews Neuroscience that it is time for a change."We believe
that names have a powerful influence on the experiments we do and the way in
which we think," they write. "Our current understanding of the avian brain
requires a new terminology."Birds have repeatedly shown human experimenters that
they deserve a higher place in the intellectual pecking order.Songbirds can
learn up to 2,000 different melodies. Scrub jays can remember things which
happen at a specific time or place, something once thought unique to
humans.African grey parrots can use words and numbers correctly in conversation
with humans. Pigeons can memorise up to 725 different visual patterns, choose
between man-made and "natural" objects and most astonishingly of all,
distinguish between Picasso and Monet, and cubism from impressionism.New
Caledonian crows in the wild routinely make and use two different kinds of tool
to get food and a crow reared in an Oxford laboratory stunned scientists with
its command of Archimedean physics when it picked up a length of wire, bent it
into a hook and started fishing out titbits from a tube.So the international
avian thinktank has proposed names that reflect the new thinking about the
brains of ptarmigans and tits, bitterns, budgerigars and buzzards."Many people
have outdated notions of what bird brains are like but there are lots of very
smart birds who do amazing things which it would be difficult to get mammals,
such as rats or dogs, to carry out," said Tom Smulders, of Newcastle
University."It's about time that people, not just scientists, appreciated birds
for what they are - a group of species which has independently evolved brains
and cognitive abilities comparable to those of mammals."

Birdbrain has long been a colloquial term of
ridicule. The common notion is that birds' brains are simple, or so scientists
thought and taught for many years. But that notion has increasingly been called
into question as crows and parrots, among other birds, have shown what appears
to be behavior as intelligent as that of chimpanzees.
The clash of simple
brain and complex behavior has led some neuroscientists to create a new map of
the avian brain.
Today, in the journal Nature Neuroscience Reviews, an
international group of avian experts is issuing what amounts to a manifesto.
Nearly everything written in anatomy textbooks about the brains of birds is
wrong, they say. The avian brain is as complex, flexible and inventive as any
mammalian brain, they argue, and it is time to adopt a more accurate
nomenclature that reflects a new understanding of the anatomies of bird and
mammal brains.
"Names have a powerful influence on the experiments we do and
the way we think," said Dr. Erich D. Jarvis, a neuroscientist at Duke University
and a leader of the Avian Brain Nomenclature Consortium. "Old terminology has
hindered scientific progress."
The consortium of 29 scientists from six
countries met for seven years to develop new, more accurate names for structures
in both avian and mammalian brains. For example, the bird's seat of intelligence
or its higher brain is now termed the pallium.
"The correction of terms is a
great advance," said Dr. Jon Kaas, a leading expert in neuroanatomy at
Vanderbilt University in Nashville who did not participate in the consortium.
"It's hard to get scientists to agree about anything."
Scientists have come
to agree that birds are indeed smart, but those who study avian intelligence
differ on how birds got that way. Experts, including those in the consortium,
are split into two warring camps. One holds that birds' brains make the same
kinds of internal connections as do mammalian brains and that intelligence in
both groups arises from these connections. The other holds that bird
intelligence evolved through expanding an old part of the mammal brain and using
it in new ways, and it questions how developed that intelligence is.
"There
are still puzzles to be solved," said Dr. Peter Marler, a leading authority on
bird behavior at the University of California, Davis, who is not part of the
consortium. But the realization that one can study mammal brains by using bird
brains, he said, "is a revolution."
"I think that birds are going to replace
the white rat as the favored subject for studying functional neuroanatomy," he
added.
The reanalysis of avian brains gives new credibility to many
behaviors that seem odd coming from presumably dumb birds. Crows not only make
hooks and spears of small sticks to carry on foraging expeditions, some have
learned to put walnuts on roads for cars to crack. African gray parrots not only
talk, they have a sense of humor and make up new words. Baby songbirds babble
like human infants, using the left sides of their brains.
Avian brains got
their bad reputation a century ago from the German neurobiologist Ludwig
Edinger, known as the father of comparative anatomy. Edinger believed that
evolution was linear, Dr. Jarvis said. Brains evolved like geologic strata.
Layer upon layer, the brains evolved from old to new, from fish to amphibians to
reptiles to birds to mammals. By Edinger's standards, fish were the least
intelligent. Humans, created in God's image, were the most intelligent. Edinger
cut up all kinds of vertebrate brains, noting similarities and differences, Dr.
Jarvis said.
In mammals, the bottom third of the brain contained neurons
organized in clusters. The top two-thirds of the brain, called the neocortex,
consisted of a flat sheet of cells with six layers. This new brain, the seat of
higher intelligence, lay over the old brain, the seat of instinctual
behaviors.
In humans, the neocortex grew so immense that it was forced to
assume folds and fissures, so as to fit inside the skull.
Birds' brains, in
contrast, were composed entirely of clusters. Edinger concluded that without a
six-layered cortex, birds could not possibly be intelligent. Rather, their
brains were fully dedicated to instinctual behaviors.
This view persisted
through the 20th century and is still found in most biology textbooks, said Dr.
Harvey Karten, a neuroscientist at the University of California, San Diego, and
a member of the consortium, whose research has long challenged the classic view.
There is a bird way and a mammal way to create intelligence, Dr. Karten
said. One uses clusters. One uses flat sheet cells in six layers. Each exploits
the basic design of having a lower brain and a higher brain with mutual
connections.
In the 1960's, Dr. Karten carried out experiments using new
techniques to trace brain wiring and identify the paths taken by various brain
chemicals. In humans, a chemical called dopamine is found mostly in lower brain
areas, called basal ganglia, which consist of clusters.
Using the same
tracing techniques in birds, Dr. Karten found that dopamine also projected
primarily to lower clusters and no higher. Later studies show numerous
similarities between clusters in the mammalian brain and lower clusters in the
avian brain. Experts now agree that the two regions are evolutionarily older
structures that lie underneath a newer mantle.
Where the experts divide is on
the question of the upper clusters in a bird's brain. Agreed, they are not
primitive basal ganglia. But where did they come from? How did they evolve? What
is their function?
Dr. Karten and others in the consortium think these
clusters are directly analogous to layers in the mammalian brain. They migrate
from similar embryonic precursors and perform the same functions.
For
example, in mammals, sensory information - sights, sounds, touch - flows through
a lower brain region called the thalamus and enters the cortex at the fourth
layer in the six-layered cortex.
In birds, sensory information flows through
the thalamus and enters specific clusters that are functionally equivalent to
the fourth layer. In this view, other clusters perform functions done by
different layers in the mammal brain.
A second group, including Dr. Georg
Striedter of the University of California, Irvine, a consortium member, believes
that upper clusters in the avian brain are an elaboration of two mammalian
structures - the claustrum and the amygdala. In this view, these structures look
alike in bird and mammal embryos. But in birds they grow to enormous proportions
and have evolved entirely new ways to support intelligence.
In mammals, the
amygdala is involved in emotional systems, Dr. Striedter said. "But birds use it
for integrating information," he said. "It's not emotional anymore."
Meanwhile, examples of brilliance in birds continue to flow from fields and
laboratories worldwide.
Dr. Nathan Emery and Dr. Nicola Clayton at the
University of Cambridge in England study comparisons between apes and corvids -
crows, jays, ravens and jackdaws. Relative to its body size, the crow brain is
the same size as the chimpanzee brain.
Everyone knows apes use simple tools
like twigs, Dr. Emery said, selecting different ones for different purposes. But
New Caledonian crows create more complex tools with their beaks and feet. They
trim and sculpture twigs to fashion hooks for fetching food. They make spears
out of barbed leaves, probing under leaf detritus for prey.
In a laboratory,
when a crow named Betty was given metal wires of various lengths and a four-inch
vertical pipe with food at the bottom, she chose a four-inch wire, made a hook
and retrieved the food.
Apes and corvids are highly social. One explanation
for intelligence is that it evolved to process and use social information - who
is allied with whom, who is related to whom and how to use this information for
deception. They also remember.
Clark nutcrackers can hide up to 30,000 seeds
and recover them up to six months later.
Nutcrackers also hide and steal. If
they see another bird watching them as they cache food, they return later,
alone, to hide the food again. Some scientists believe this shows a rudimentary
theory of mind - understanding that another bird has intentions and beliefs.
Magpies, at an earlier age than any other creature tested, develop an
understanding of the fact that when an object disappears behind a curtain, it
has not vanished.
At a university campus in Japan, carrion crows line up
patiently at the curb waiting for a traffic light to turn red. When cars stop,
they hop into the crosswalk, place walnuts from nearby trees onto the road and
hop back to the curb. After the light changes and cars run over the nuts, the
crows wait until it is safe and hop back out for the food.
Pigeons can
memorize up to 725 different visual patterns, and are capable of what looks like
deception. Pigeons will pretend to have found a food source, lead other birds to
it and then sneak back to the true source.
Parrots, some researchers report,
can converse with humans, invent syntax and teach other parrots what they know.
Researchers have claimed that Alex, an African gray, can grasp important aspects
of number, color concepts, the difference between presence and absence, and
physical properties of objects like their shapes and materials. He can sound out
letters the same way a child does.
Like mammals, some birds are naturally
smarter than others, Dr. Jarvis said. But given their range of behaviors, birds
are extraordinarily flexible in their intelligence quotients. "They're right up
there with hominids," he said.