Date of Award


Degree Type


Degree Name

Master of Science




Biology (MS)

First Advisor/Chairperson

Dr. Alec R. Lindsay


The study of plumage is a foundational aspect of ornithology, and the features of even a single feather can provide valuable information on an individual’s health, sex, or age. Recent discoveries on the abilities of birds to see in the ultraviolet (UV) spectrum has led to study of the UV-reactive characteristics of bird plumage and the biological significance of such plumage. Long-eared owls (Asio otus) possess a demonstrative capability to see UV light, and their plumage contains deposits of UV-sensitive pigments that fluoresce bright red when exposed to UV light. Little is understood about the origin and function of these pigments, and few studies have attempted to describe their variation within a species. In this study, I describe phenotypic variation within the long-eared owl, with an emphasis on both visible and ultraviolet aspects of plumage coloration. I used a molecular genetic sexing assay to evaluate a published method of sexing long- eared owls in the field based on melanistic pigmentation. I found that although some long-eared owls exhibit distinct plumage dimorphism in the visible spectrum, there also is an intermediate polymorphism that greatly limits the number of individuals that can be classified. I also investigated variation in fluorescent pigmentation through the use of a fluorescence detector and found evidence that fluorescent pigment concentration varies both between the sexes and between juvenile and adult plumage.

Access Type

Open Access

Justification for Restricting Access

Although a full 5 year embargo may not be necessary, we request that a restriction be put on this thesis while we finalize the submission and publication of these papers to a peer reviewed journal.

Available for download on Wednesday, July 08, 2026

Included in

Ornithology Commons