102, NPB Animal Behavior Study questions for Chapter 2 Winter 2011 1. 2. What is the syrinx, and how is it used by birds to produce sounds? Be as specific as you can about how different parts contribute to sound production. Imagine an experiment where you begin with a fully adult male bird that has crystallized its song, and you then infuse a local anesthetic into the syrinx that specifically targets the muscles controlling the left side. This procedure numbs those muscles and prevents the bird from regulating air flow through the left bronchus. That is, the left bronchus would remain completely open all the time because the bird cannot contract the left syringial muscles. How do you think this procedure would affect the song of the bird? Be as specific as you can about the effects it would have on the different elements of the song. What would happen if instead you inserted a little plug into the left bronchus to prevent all air flow through it? Explain what is meant by the statement that songbirds have two voices and describe anatomical and experimental evidence consistent with this idea. Use the example of red-winged blackbird song to explain why Tinbergens choice of the term survival value was not ideal. What term would you suggest using instead, and why? Describe how the song type matching studies of free-living song sparrows clearly have both proximate and ultimate interpretations. Open Ended Song Learners are believed to be able to keep memorizing new songs to produce well beyond their first year of life, and possibly throughout their lives. One of your friends tells you that song sparrows must be open ended song learners and cites the evidence that young males establishing a territory for the first time appear to be able to crystallize songs that are close matches to those of their neighbor males. How would you respond to this assertion? Define a song dialect, and contrast song dialects with at least two other forms of inter-individual variation in song. Explain what kind of information you would need in order to distinguish among all of these forms of interindividual variation in song. Give one proximate and one ultimate explanation for why the songs of birds living in different habitats (e.g., densely-vegetated versus more open) might emphasize different sound pitches. Do the same for birds living in urban versus wild woodland habitats. What are the stages of song learning in male songbirds, and what is going on in each stage? One of the key features of so-called critical period songbirds is that memorization of new songs is only supposed to be possible during a brief critical period early in life. Imagine that you are studying a species of songbird believed to be a critical period learner, but that you discover that the song repertoire of males tends to increase from one year to the next as the males age. Could this increase in song repertoire with age occur even if the birds really are critical period learners? If not, why not? And if so, how? What is a neural template for song learning? Describe how you think the neural template might function in song learning of an individual male bird that has received tutoring by tape recordings of conspecific males as compared with in an individual male that has received no tutoring at all. A good answer will discuss the hypothesized role of the neural template in both motor production and learning. Which of the following statements would you say better describes the neural template for (a) a white-crowned sparrow (an oscine songbird) and (b) an eastern phoebe (a sub-oscine songbird)? 1. The neural template provides a blueprint for what the bird is going to sing. 2. The neural template provides a guide for the learning process. Defend your answer. What is the significance of differential gene expression in different song control regions during development? Sketch the main elements of the caudal production pathway and the rostral learning circuit of a typical male songbird. How does the song system of a female of a species that doesnt sing at all, such as the zebra finch, differ from that of males of that species? One major difference between male and female zebra finches is that the neural connections between HVC and RA never develop fully in females, unlike males. Do you think this is likely to have a greater effect on the ability of a female to sing, or on her ability to learn to recognize the songs of different individual males? Why? Consider two alternate hypotheses regarding the evolutionary origin of song learning in birds: (1) song learning evolved independently three times to produce the current pattern of learning and non-learning songbird orders, or (2) song learning evolved once and then was subsequently lost along some lineages to produce the current pattern of learning or non-learning songbird orders. Which of these two hypotheses do you favor, and why?
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Note that to give a complete answer you should draw on both phylogenetic and neuroanatomical/neurophysiological information. Following up on the previous question, imagine that some new data are collected showing that the swifts (Apodiformes) actually learn their vocalizations. How would this affect your answer to the previous question (or would it affect it?)? What if the new data instead showed that the Columbiformes (pigeons and doves), Gruiformes (cranes and rails) and Ciconiiformes (herons and egrets) learned their vocalizations? And what if the new data instead showed that the Strigiformes (owls) learned their vocalizations? Youll need to consult the phylogenetic diagrams shown in the book and presented in lecture in order to answer this and the previous question. Describe some evidence that the eastern phoebe does not learn its songs by copying sounds it hears as a youngster. Phoebes and other flycatchers belong to a relatively basally-derived group of songbirds called the sub-oscine songbirds, none of which are currently known to learn their vocalizations (despite being songbirds). Does this observation have any bearing on the question of whether song learning originated multiple times in the birds, or just once? How does experience during territory establishment affect the song learning process of male songbirds? Does it contradict the idea that male white-crowned sparrows are critical period learners if the song that males choose to crystallize depends on experience they have at the time of territory establishment, when they are well over 200 days old? Why or why not? Note that you should discuss the concept of overproduction in order to answer this question well. How can male song sparrows use different song types to control the intensity of an aggressive interaction with a neighboring male? Discuss this phenomenon in both proximate and ultimate contexts. Describe some evidence suggesting that female songbirds may use male song characteristics to evaluate the quality of the singer. Which of the following hypotheses are legitimate alternatives to one another? Explain your rationale. (1) Singing the local dialect improves the ability of males to exclude rival males from their territories. (2) Singing the local dialect makes males more attractive to local females. (3) Males sing the local dialect because they were tutored only with that song type. (4) Males sing the local dialect because they never hear other dialects until after the critical period for song memorization has ended. (5) Males sing the local dialect because they select songs for crystallization from the overproduced repertoire based on the songs they hear most at the time they settle to breed. There are many possible answers to the question, Why do male songbirds sing the particular songs that they do? Give several different possible answers, at least one that relates to each of Tinbergens 4 questions. Provide some evidence for each, and explain which of Tinbergens questions each relates to and be sure you understand whether you have provided a proximate or an ultimate answer in each case. In general terms, what are these answers to this type of question called? (Hint: The answer names a fundamental component of the scientific method.) Describe the evidence that male white-crowned sparrows do not need to be tutored with complete songs in order to learn to reproduce essentially normal complete songs. What does this tell us about the nature of the template for song learning/production and how it influences the nature of songs produced during adulthood? Describe some evidence indicating that male birds use song to communicate with one another. How about evidence that they use song to communicate with females? Consider the following question: Why do white-crowned sparrows possess an innate tendency to select conspecific song to memorize out of a complex acoustic environment? For each of the following hypotheses based on this question, indicate what level of analysis it addresses and explain your answer. a. The earliest oscine songbirds evolved this trait as a means of guaranteeing that learned song patterns would exhibit essential species-typical attributes. b. They possess a neural template that causes them to be selectively attentive to sounds with characteristics similar to the species typical song. c. Certain neurons in the developing white-crowned sparrow HVC are strongly resistant to environmental modification of their eventual selective auditory response characteristics, showing pronounced preference for white-crowned sparrow-typical songs regardless of early experience. d. This attribute prevents males from learning inappropriate songs that females will not consider attractive. Describe the evidence that female red-winged blackbirds are more discriminating when it comes to song than males are. Provide one proximate and one ultimate explanation for this fact.
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