BOSTON, MASS - Birds are remarkably adept at tasks involving communication, navigation, and certain types of memory, researchers have found. In some unusual cases, these abilities may even surpass those of humans. Although we tend to think of cognition as the purview of humans and our closely related kin, it's time to extend the courtesy to birds as well, scientists said today at the American Association for the Advancement of Science (AAAS) Annual Meeting.
It's easy to accept that non-human primates, with whom we share so many physical similarities, are capable of cognition--generally defined as the ability to take in large amounts of information about the world and use it in decision-making. Or that dolphins and other cetaceans, with their large brains and often human-like behavior, are as well.
Birds, however, are a different story. They look nothing like us and act nothing like us. Evolutionarily speaking, birds and humans are miles apart. Lest we underestimate the bird brain, however, some birds do have a flair for certain types of cognition.
For example, there's Griffin, a Grey parrot, who lives in the lab of Irene Pepperberg, at MIT and Brandeis University. Griffin has recently begun combining objects in specific orders, and doing the same with vocal labels. Such behavior once thought exclusive to humans, great apes, and monkeys, according to Pepperberg.
"The simultaneous emergence of both vocal and physical combinatorial behavior was thought to be a purely primate trait, derived from primate brain area. The fact that we are finding this in animals so far removed from primates is exciting," Pepperberg said.
Children begin to order word combinations and object combinations at approximately the same time in the development process. Researchers have proposed that a language-related region in the brain, called "Broca's area," controls both these abilities during the earliest stages of development. According to this hypothesis, this type of behavior may be the very first stages of using syntax, the word patterns involved in language.
Dr. Pepperberg doesn't think Griffin is necessarily using syntax when he orders plastic cups in certain patterns and says word combinations that roughly correspond to human language (such as "green birdie," or "do you want grape?"). But she does think it's an example of "rule-governed behavior," the understanding that complex tasks must be done according to a certain order.
Birds don't have a Broca's area, but it does seem that the neural machinery involved in making ordered word and object patterns is not unique to primates, according to Pepperberg. Such machinery may have evolved separately in birds and primates, or it may have been inherited from an ancient ancestor, common to both groups.
If the second possibility is correct, the neural basis for this type of behavior may have been passed onto other groups as well.
"Other vertebrates may have similar abilities as well. It may just be that we haven't looked for them yet," Pepperberg said.
Another way in which some birds communicate according to rule-governed behavior is through their songs. Just like human infants learning to speak, young songbirds, parrots, and hummingbirds must learn and memorize a repertoire of songs.
"The special abilities that many songbirds have, just like we have, relate to the ability to learn a vocal communication system. But our closest living relatives, the non-human primates, cannot," said Donald Kroodsma, of the University of Massachusetts in Amherst. "Why learning evolved is one of the big mysteries of animal communications. We'd like to think that looking at the songbirds, we might find some of the answers,"
Based on his studies of a songbird called the sedge wren, Kroodsma thinks that song-learning may be related to birds' neighborly instincts.
Songbirds can learn up to 2000 different songs. These songs usually include those of the birds' neighbors, whom they've become familiar with after returning to same site year after year.
Sedge wrens, however, don't learn other birds' songs; they just make up their own, according to Kroodsma. They live in the grasslands of North America, are unusually nomadic, never settling down long enough to get to know their neighbors.
Thus, song-learning may have evolved as a means for social songbirds to communicate with neighbors.
It's too early to say how broadly this idea may apply across the animal kingdom, but Kroodsma plans to start by studying other nomadic grassland birds.
Some birds also seem to be capable to a certain degree of logical reasoning, according to Alan Bond and Alan Kamil of the University of Nebraska.
Bond and Kamil have found evidence suggesting that social jay species may be capable of a cognitive process called "transitive reasoning." This process can be described in terms of logic, that "if A is greater than B, and B is greater than C, then A is greater than C."
According to the so-called "Machiavellian hypothesis," which has been formulated with respect to primates, the ability to use this type of reasoning may have evolved in social animals. In this context, transitive reasoning would allow individuals to infer social relationships among members of a large population.
The Machiavellian hypothesis may apply to birds, as well, according to Bond and Kamil. They tried teaching two types of jays, from a social species and a non-social species, this type of reasoning. They trained the birds to choose A over B, B over C, and so on, in order to obtain a reward. The researchers found that social birds were significantly better at choosing, for example, B over D, when first presented with this particular pair than non-social birds.
Social jays, in fact, appeared to be similar in their reasoning abilities to highly social primates. Additional tests with other pairs of social and nonsocial birds are planned.
Another department in which birds clearly outdo other, gravitationally challenged animals, is navigation. Able to migrate across continents year after year, and to remember numerous landmarks, birds must have some special component in their brain that endows them with such superior navigating skills-or so believe Kamil and Verner Bingman, of Bowling Green State University.
Certain birds, such as nutcrackers and jays, store thousands of seeds in the fall, each in a different place, and them find them again during the winter. Male and female pinyon jays mate for life, caching seeds together in the fall, and breeding in the early spring.
How do these birds remember where they stash a particular seed? Kamil has found that they use multiple landmarks, most likely remembering a seed's direction in relation to each landmark and then finding it according to the intersection if the two lines.
Kamil's experiments also suggested that the birds use a third landmark for each hiding place, which seems to help orient them. The third landmark may be necessary because the birds' internal compass has a certain amount of error, according to Kamil.
Scaling down to the neurons involved in navigation, new findings have given Bingman an idea of how birds' brains might be organized to remember large amounts of spatial information. Bingman investigated the pigeon hippocampus, a brain region known to be involved in learning and remembering spatial information.
To his surprise, the pigeon hippocampus turned out to be essentially similar to the hippocampus of the rat, an animal that doesn't share birds' spatial superiority. Bingman therefore believes that the differences lie in structures that evolved separately in birds and mammals, specifically the "hypertrophied anterior forebrain," as it's called in birds, and the "neocortex," as it's called in mammals.
Both of these later-evolved structures hook up to the hippocampus, and Bingman thinks that the birds' version does so in a way that allows them to avoid getting lost. It may someday be possible to use what we learn from the bird brain for our own purposes.
"In theory, you might design some type of navigational machine based on this," Bingman said. "But that's just science fiction at this point."
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