Lecture2BNotes - Slide10: categories,shownonthisslide 11::...

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Chapter 2 Lectures Slide Notes 1 Slide 10: We’ll go through some different ultimate functions of song and I’ll group them into several categories, shown on this slide. 11: Effectiveness as a signal in different environments: Great tits are small songbirds that occupy a wide geographic range in Europe. This slide shows that great tits living in the forests (where vegetation is thick and trees close together, left column of the figure) tend to sing songs emphasizing lower pitches than do great tits living in woodlands (where vegetation is sparse and trees widely spaced, right hand column). Although there could be multiple adaptive (fitness related) reasons for this pattern, one potential explanation (hypothesis) is that the physical structure of the environment dictates what makes a good signal. Specifically, in densely vegetated forests, high frequency sounds attenuate (lose power) more quickly than they do in more sparsely vegetated habitats. This can be shown empirically to be true, and also makes intuitive sense because the short wavelength of high frequency sounds makes it possible for transmission of those sounds to be more dramatically disrupted by physical barriers (tree trunks, branches, leaves, etc) than is the case for longer wavelength low frequency sounds. The data presented in this figure are consistent with this idea, although of course this does not mean the data prove this hypothesis. The data are simply consistent with it. It would be worth while for you to contemplate this figure with proximate causation in mind as well: What proximate explanations of this pattern can you come up with? 12: Species recognition is an extremely important function of song. This figure shows a sound spectrogram of a male red winged blackbird song, as well as the chatter that a female redwing often gives when she hears a song of her own species. The buzzy part between about 0.75 seconds and 1.6 seconds is the male song, and the sequence of marks (labeled “chatter”) toward the end are the female’s response. She would be very unlikely to give that call if she didn’t hear the song of a male of her own species. 13: This figure shows just how discriminating female red winged blackbirds can be. They give more displays (in this case, copulation solicitation displays, demonstrating her willingness to mate with a male) when they hear red winged blackbird song than when they hear a control stimulus, in this case swamp sparrow song (swamp sparrow is another species of bird that lives in similar habitat, so this song is a reasonable control stimulus to use). Female redwings are even able to tell the difference between the “real thing” (song of a genuine male red winged blackbird) and a good copy of it (a mockingbird’s copy of a red winged blackbird song; right hand panel of the figure).
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This note was uploaded on 05/30/2009 for the course NPB 102 taught by Professor Hahn during the Winter '09 term at UC Davis.

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Lecture2BNotes - Slide10: categories,shownonthisslide 11::...

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