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The ecology and development of alternative vocal learning programs in birds
Non-imitative vocal development strategies, such as improvisation and invention, have been poorly documented compared to imitation, but evidence is mounting that they play an important role in the vocal development of some species, and at least a partial role in the vocal development of many other species. Currently the ecology and ontogeny of these alternative vocal development strategies are poorly understood and largely unstudied in all but a handful of species. In Chapter 1, I define improvisation and invention based on what we currently know and discuss some of the underlying developmental steps. I also suggest some potential areas for future research. In Chapter 2 I test the hypothesis that the predominant vocal development strategy is correlated with seasonal movement patterns by comparing song development between migratory Massachusetts and sedentary California red-winged blackbirds (Agelaius phoeniceus). The results of this study support other studies which have found a correlation between vocal development strategy and seasonal movement patterns. Migratory Massachusetts red-winged blackbird males improvise many more songs in their repertoires, and imitate much less from the tutor models, than do the sedentary California males. The songs improvised in the laboratory largely overlapped in structure with songs from wild males. In Chapter 3 I further test the hypothesis that laboratory-developed improvised songs function like normal conspecific songs and are not abnormal byproducts of an artificial learning environment. Using a paired playback design, I compare the response of wild males to playback of both these improvised songs and wild-recorded songs from other populations. The results of these playbacks indicate that, for the most part, wild males regard these laboratory-improvised song types as normal conspecific song. In Chapter 4 I study the ontogeny of improvised songs under social learning conditions and confirm the ability to improvise in migratory Massachusetts Common Grackles (Quiscalus quiscula) and possibly in more sedentary individuals from Florida. Male grackles from Massachusetts all produced better copies of the songs of the adult tutors earlier in development than they did later in development. Common Grackle males appear to be diverging from both the adult tutors and each other so that each male's song occupies a unique acoustic space.
Goodwin, Elijah Anthony, "The ecology and development of alternative vocal learning programs in birds" (2008). Doctoral Dissertations Available from Proquest. AAI3315538.