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Ofer Tchernichovski is an Associate Professor of Biology at The City College of The City University of New York (CCNY-CUNY). He and the students in his lab use the songbird—and in particular, the zebra finch—to study mechanisms of vocal learning. Like a human infant first beginning to babble, the young zebra finch learns to imitate complex sounds during a critical period of development. Why the adult bird loses the ability to imitate is still a mystery. The lab uses brain imaging and sound analysis to better understand the bird's behavior and the dynamics of vocal learning. In addition, the lab aims to uncover the specific genetic and physiological processes that underlie song learning. |
On July 22, 2008, Ofer Tchernichovski answered selected viewer questions about how birds learn to sing and how this relates to vocal learning in humans. Please note we are no longer accepting questions, but see Name That Tune as well as our links and books section for additional information. Q: This may seem like a silly question, but I found the area that Mr. Tchernichovski investigates very interesting. As a high school student, it could be a potential career path for me. How would Mr. Tchernichovski's occupation and field be classified? As Genetics? Ornithology? Thank you. A: Hi Ainara, I am very happy that you are considering an academic career! I am classified as a neuro-ethologist, namely I study mechanisms of natural behaviors. My bachelor degree is in biology and my Ph.D. is in zoology, but this is not the only possible track. Each of my colleagues in the birdsong field has different training: some are molecular biologists, others are physicists, psychologists, etc. Each one of us has a different expertise, which makes our field more interesting. Good luck and all the best! Ofer Q: Why do birds sing? A: Hi Chi, It is written in the books that birds sing to attract mates and defend their territories. Of course, males of many animal species put effort in attracting mates and defending territories using other means, e.g., marking the territory borders. Is there a qualitative difference between birdsong and other means of defending territories and attracting mates? We do not know the answer to this question, but most people agree that there is something very special about birdsongs: Songs are learned, and birds have local cultures of singing in a certain way (local dialects). Further, songs are often rather aesthetic (maybe even musical). So when we ask "why do birds sing," we are sometimes driven toward questions that are difficult to test: Is there a non-practical (not evolutionary-driven) component to the singing behavior? Are the beauty and complexities of birdsongs unique in any sense? There is beauty in many behavioral patterns, so I am not sure if birdsongs are unique, or just easier to appreciate. I hope that as we learn more about song structure and development, we will be able to assess the qualities of song in ways that give more justice to their beauty. Take care, Ofer Q: If zebra finches learn their song by imitation, shouldn't there be very little song diversity? And if so, how can the females judge the males' songs if they all sound the same? A: Wow-that's an excellent question! It seems that zebra finches do not like to have a song that is too similar to that of other males. For example, if five male siblings are tutored by their father, only one or two of them will accurately imitate his song-the rest of the siblings diverge and sing different songs. There is an interesting parallel to this effect in population genetics. It is called evolutionary stable polymorphism: For example, different people have different hair color, and this diversity persists over many generations. If most people find one hair color (e.g., blond) more attractive, how come blond people are not becoming more common in each generation? One mechanism that can preserve polymorphism is called "frequency dependent selection," for example, blond hair is not considered as attractive in Scandinavia, where it is very common. Back to songs, polymorphism of songs in a group might be a result of frequency dependent imitation (young birds selecting some rare sounds from their tutors) or frequency dependent sexual selection (females preferring songs with some rare qualities, while some juveniles prefer to imitate their fathers). Keep asking questions, Ofer Q: Do any other birds show evidence of being as intelligent as parrots? A: Hi Mary Ann, Several bird species show behaviors similar to the ones you see in parrots, including imitation of human speech (myna birds, some crows), sophisticated usage of tools (jays & crows), and even perception of complex grammars (starlings), and I can continue on and on, but note that I did not use the term intelligence. People often ask me about intelligence in animals, and I am getting nervous when trying to answer ;-) The reason is that intelligence is in an anthropocentric (human like) term: Namely, we do not know how to test for intelligence in a manner that is independent of the limitations of our own intelligence, and I do not even like to think about different people as more or less intelligent (although sometimes it is difficult to avoid doing so). As to animals, all animals I have ever looked at show quite amazing behaviors, combining behavioral patterns that seem "hardwired" with behavioral patterns that are learned. Take care, Ofer Q: Every week my husband and I say that this is the best episode ever! Thanks to NOVA for all of them! Here is my question: In February, when our spring season is already in bloom in Tucson, Arizona, we hear mockingbirds singing their little hearts out. I have never heard the same tune twice, and I wonder about the relationship between their songs and the language research we heard about on tonight's production. I hope you might have an answer for me. Thank you. A: Hi Barbara, I do not have a good answer... Mockingbird song has mockingbird-like patterns in it even when the bird imitates other species. The bird often repeats the song of one species four times and then moves to the song of the next species. Aside from that, we know little about mockingbirds song structure-how it comes about and how their songs function. Almost every morning now, while waiting for the train, I watch a mockingbird sing continuously one song after the other while hopping up and down and even while flying. All I can say is, wow! Take care, Ofer Q: Hi, I have a few questions: What protein does the FoxP2 gene encode for, and what exactly are the functions of this protein? In the segment, they mentioned that the FoxP2 was up-regulated at times when the birds learned songs, then down-regulated after they are done. Young children seem to easily pick up other languages, but as they grow older it gets more difficult to learn; is it possible that this FoxP2 could be up-regulated in humans to help older people learn other languages as easily as children? Thank you for your time. A: Hi Jason, Before I answer let me make a few comments: In most cases, a gene does not explain a behavior in any simple manner, and FOXP2 is no exception. When a bird sings, or learns how to sing, many (even hundreds) of genes are changing their expression over large brain areas-some increase their proteins and others decrease them in a well-orchestrated manner. The proteins of the early genes are activating or inhibiting other genes, and so on. When brain cells (called neurons), are engaged in a certain activity (say in singing, or in listening to songs) they are expressing genes, changing the chemical soup of proteins that surrounds them, which in turn changes the state of those neurons over longer time scales, and "the proof is in the pudding." Now back to FOXP2: The FOXP2 protein is a transcription factor, namely, it is a protein that regulates the expression of other genes. To my knowledge, most of those target genes were not yet identified. In humans, as in birds, vocal learning (acquiring a spoken language) is much easier in juveniles than in adults. We call it "the sensitive period." We do not know if FOXP2 has anything to do with the closure of the sensitive period for song learning, but it shows high expression during song learning and low expression thereafter, which could suggest some involvement in this process. Once we identify what controls the opening and closure of the sensitive period for song learning, there are several possible applications. Helping adult people to learn a second language is a rather remote option, but facilitating recovery of devastating strokes is more likely. Recovery from stroke often requires re-learning of basic skills, and children can learn those much better than adults. This is why it is useful to study FOXP2 and other genes in birds: If we figured out that FOXP2 can help adult birds learn songs, it would make sense trying it in humans. Q: It seems that Chomsky's Universal grammar might apply to species other than Homo sapiens. Are there instances where, for example, an Australian finch has learned the song of another species whose song is distinctly different? Also, is there anything known about the neural circuitry that links the 'knowledge' module with the area that is responsible for production of the sounds? A: Hi Gerald, Your question touches on some of the most difficult issues in song learning. Indeed, birds can learn songs of other species, and several viewers asked me about mockingbird imitations of other species. Although most songbirds do not imitate other species in nature, laboratory studies show that they have the ability to do it. A recent study by Tim Gardener and Fernando Nottebohm showed that canaries, which usually sing songs of repeated syllables [AAAABBBCCCCDDDDDD...] can learn to sing songs like [ABCDE...]. But interestingly, at some point they suddenly "change their minds" and shift the syllable syntax to repeated syllables [AAABBBBBCCC...]. What makes them "change their minds"? Interestingly an injection of testosterone is sufficient to trigger that change. So, in the beginning the bird just imitates, but then it learns to say "no," just like children do ;-) Take care, Ofer Q: Is there any area of study regarding birds, brains, and apraxia? We have a four-year-old daughter recently diagnosed with apraxia and are trying for find any treatments that may aid her. A: Hi Jeff, I do not know if there is a link between the two, and I am not aware of anyone studying it, although it makes sense to try. Speech apraxia is (to my very limited knowledge) a coordination problem, not a cognitive one. It might be caused by damage to the motor speech centers in our brain. One amazing feature of the birdbrain motor song-system is that brain cells (neurons) of those centers can be replaced by new neurons, which then rewire the brain. This rewiring is associated with song learning, so there is a hope that understanding this mechanism (called adult neurogenesis) in the bird, will help us one day to repair damage in human brains. I wish I could give you a better answer. All the best, Ofer Q: I'm curious about parasitic birds such as cowbirds. How do they learn the correct song if they are raised by foster parents? For that matter, how do they know they are cowbirds? A: Hi Marj, That's an excellent question that puzzled scientists for many years! The answer is that they develop a "default" cowbird song regardless of their host. However, cowbirds have local dialects-so they must imitate each other too! Indeed, once they fledge from their host's nest, they somehow find other cowbirds and form juvenile flocks. Social interactions and aggression help shape their songs so that the more dominant males develop more attractive songs. The more attractive the song is (for females), the more irritating it is for the males. So, when a male cowbird sings an attractive song he risks more attacks. In contrast to many other birdsong species, raising cowbirds in isolation results in a very attractive "default" song-since there is no one to challenge the isolate bird to decrease the appeal of his song. Regards, Ofer Q: Why doesn't my canary sing? A: Hi, Well, if it is a male canary, and if it is adult and happy, it should be singing. But canaries only sing seasonally-during spring and then again during fall. Female canaries might sing, but not much, and it is difficult to tell a male canary from a female canary. So most likely you have a female. Regards, Ofer Q: I read that you are trying to understand the reasoning behind the zebra finch loosing the ability to learn songs as it ages. I am curious what the differences in brain function are between a zebra finch and a mockingbird. As far as I know, mockingbirds continue to learn. Or do they reach an age when it becomes hard or impossible for them to learn as well? A: Hi Tim, That's a very interesting question. We divide songbirds into developmental learners (like the zebra finch) and open-ended learners (like canaries and mockingbirds). In some open ended learners, like canaries, song learning occurs also during narrow time windows, but those re-occur each season. In canaries, seasonal song learning is triggered by changes in photoperiod (e.g., longer days), which then cause gene expression changes, hormonal changes, and recruitment of new brain cells (neurons) into the song-system. Only then can the canary start learning a new song. However, I am not aware of any established technique that can allow song imitation to occur in an adult zebra finch, or in any other developmental learners. Take care, Ofer
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