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Quantifying the avian pelvis: Statistical correlations of lifestyle to pelvic structure among non -passeriform birds

Rebecca George Mattison, University of Massachusetts - Amherst

Abstract

To separate functional from phylogenetic pelvic differences in Aves, seventy-seven birds were measured and statistically analyzed to define the characters that unite them into function groups, and to identify the characters that separate the function groups from each other. Four Major Function Groups were identified: Birds of Prey (Chapter II) Waterbirds (Chapter III), Ground birds and Stalker-wader birds (Chapter V). Birds of Prey statistically separate into Air predators and Scavengers. Waterbirds statistically divide into Surface swimmers, Wing-propelled divers, and Foot-propelled divers. A suite of pelvic characters (Level One indicators) can separate nonpasseriformes birds into function groups. These are: length to width ratio of the pelvis, iliac angle, relative iliac surface areas and pre-acetabular ilium proportions. A second suite of characters (Level Two indicators), used by themselves, shows trends, but do not completely separate the function groups. These are proportional length of lower leg components, and femur length: pelvis length ratio. Combining the identified characters in Principal Component Analysis and Discriminant Function Analysis produces a good split among the function groups. When all of the birds are combined into a single analysis (Chapter V), using Level one and Level Two characters, the plots generated have Stalker-wader birds at the center, with three groups radiating out. One arm is Ground Birds, another is Waterbirds, and the third is Birds of Prey.^ Pelvic musculature dissections of a representative from each group are compared (Chapter VI). The picture drawn from the muscle data is different. The muscle data suggest that Ground Birds are the central group. Ground Birds (represented by a pigeon) have leg/pelvic muscles neither specialized for specific femoral movements, nor for specific tibiotarsal movements. No particular group of muscles is hypertrophied, and no major groups are reduced or missing. The other three function groups of birds show some degree of specialization, either by reducing or accentuating muscles, or by losing muscles completely. The result is a statistical portrait of four bird function groups that has implications for the sequence of morphological changes seen in avian radiations of the Tertiary. ^

Subject Area

Biology, Anatomy|Biology, Zoology

Recommended Citation

Rebecca George Mattison, "Quantifying the avian pelvis: Statistical correlations of lifestyle to pelvic structure among non -passeriform birds" (January 1, 1998). Doctoral Dissertations Available from Proquest. Paper AAI9841895.
http://scholarworks.umass.edu/dissertations/AAI9841895

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