Event Title
Regional and Interspecific Variation in Crown Feather Reflectance in Two Hybridizing Warblers
Location
University of Richmond, Richmond, Virginia
Document Type
Poster (UR Campus Access Only)
Description
Golden-winged warblers (GWWA) and blue-winged warblers (BWWA) are two North American wood warbler species who are known to hybridize. The hybrids show intermediate plumage patterns and are able to successfully back-cross with either of the parent species. Over the past couple of decades, GWWA populations have been declining, while BWWA populations have been increasing or stable. This may be due to many factors, such as competition with BWWA, land use changes resulting in less available shrubland habitat, or possible detrimental effects of hybridization. In this study, we attempt to understand what factors impact crown feather reflectance in this hybrid complex where all individuals have yellow crown feathers that are likely an important signal in competitive interactions and/or mate attraction. Specifically, we will assess the roles of sex, species, age, and geographic region in explaining variation in crown feather reflectance. We used a spectrometer to measure the percent reflectance across the visible and UV spectra, and calculated violet-blue chroma, visible intensity, and UV brightness to characterize plumage ornamentation and serve as the response variables in our analyses. The best model across all birds included a sex by species interaction where GWWA females were significantly less ornamented than GWWA males, but BWWA males and females were similar. If males in this complex select female mates based on plumage, female BWWAs may be preferred and this could facilitate directional hybridization. In an analysis of males only, the best model included species and region as predictors. This suggests that regionally varying environmental factors may impact plumage ornamentation. This makes sense as yellow feathers are carotenoid-based and acquired through the diet; however, the degree of heterospecific interactions also varies regionally and could impact plumage variation. Further understanding factors that influence plumage variation within and among golden-winged and blue-winged warblers could uncover potential mechanisms facilitating hybridization in this species complex. This study represents only 50% of the samples collected thus far, and we anticipate that a larger sample from across a broader geographic region may lead to more interesting findings and generate additional hypotheses.
Regional and Interspecific Variation in Crown Feather Reflectance in Two Hybridizing Warblers
University of Richmond, Richmond, Virginia
Golden-winged warblers (GWWA) and blue-winged warblers (BWWA) are two North American wood warbler species who are known to hybridize. The hybrids show intermediate plumage patterns and are able to successfully back-cross with either of the parent species. Over the past couple of decades, GWWA populations have been declining, while BWWA populations have been increasing or stable. This may be due to many factors, such as competition with BWWA, land use changes resulting in less available shrubland habitat, or possible detrimental effects of hybridization. In this study, we attempt to understand what factors impact crown feather reflectance in this hybrid complex where all individuals have yellow crown feathers that are likely an important signal in competitive interactions and/or mate attraction. Specifically, we will assess the roles of sex, species, age, and geographic region in explaining variation in crown feather reflectance. We used a spectrometer to measure the percent reflectance across the visible and UV spectra, and calculated violet-blue chroma, visible intensity, and UV brightness to characterize plumage ornamentation and serve as the response variables in our analyses. The best model across all birds included a sex by species interaction where GWWA females were significantly less ornamented than GWWA males, but BWWA males and females were similar. If males in this complex select female mates based on plumage, female BWWAs may be preferred and this could facilitate directional hybridization. In an analysis of males only, the best model included species and region as predictors. This suggests that regionally varying environmental factors may impact plumage ornamentation. This makes sense as yellow feathers are carotenoid-based and acquired through the diet; however, the degree of heterospecific interactions also varies regionally and could impact plumage variation. Further understanding factors that influence plumage variation within and among golden-winged and blue-winged warblers could uncover potential mechanisms facilitating hybridization in this species complex. This study represents only 50% of the samples collected thus far, and we anticipate that a larger sample from across a broader geographic region may lead to more interesting findings and generate additional hypotheses.
Comments
Department: Biology
Faculty Mentor: Dr. Kristine Grayson, and Dr. Lesley Bulluck