Date of Award

1999

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Renewable Natural Resources

First Advisor

Alan D. Afton

Abstract

Musk Ducks (Biziura lobata) exhibit a number of unusual morphological and behavioral traits. The most notable of these include: greatly abducted hind-limbs for underwater swimming efficiency, extreme sexual size dimorphism and pronounced structural dimorphism, lek display activity, elaborate sexual display repertoires, and the distinctly non-waterfowl-like trait of provisioning young with all their food from the time of hatch until fledging. Despite such peculiarities and obvious theoretical potential in the areas of comparative morphology, sexual selection, and brood ecology, few studies of Musk Ducks have been undertaken, and those to date have been either small in scope and design, or focused on captive birds. I present here an investigation of historical, ecological, and social aspects of Musk Duck biology that hitherto have gone unstudied or generally remained unnoticed. Based on phylogenetic analyses of mtDNA sequences of the cytochrome b gene, I conclude that Musk Ducks are not close relatives of other stifftail ducks (e.g., Nomonyx, Oxyura) as previously surmised, but rather, a more distant, independently derived lineage in which hind-limb morphology and other correlated diving adaptations have evolved convergently. Multivariate analyses of sixteen anatomical measurements, likewise, suggest that sexual selection has played an important role in determining overall patterns of male morphometric variation. Niche divergence, on the other hand, can not be ruled out and might also be a viable explanation of observed levels of sexual size dimorphism. Time-budget and activity-pattern information generally support these conclusions, revealing pronounced differences between sexes, in addition to large scale patterns of spatial and temporal variation. Acoustic analyses of sexual advertising displays reveal fixed cultural differences between eastern and western populations consistent with Bassian faunal elements, in addition to previously undescribed variation within populations. Comparisons with immature wild birds and captive adults also indicate that dialects are learned.

ISBN

9780599252394

Pages

169

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