Date of Award

Fall 12-15-2023

Level of Access Assigned by Author

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology and Environmental Sciences

Advisor

Pauline Kamath

Second Committee Member

Allison Gardner

Third Committee Member

Anne Lichtenwalner

Additional Committee Members

Brian McGill

Brian Olsen

Abstract

Avian health encompasses the physical, physiological, and behavioral well-being of birds. Assessing avian health is not only important for the conservation and management of wild birds and the recreational economy, but also for the management of infectious diseases that threaten public health and agriculture. Birds, comprising approximately 10,000 species and an estimated 50 billion individuals worldwide, are known to be involved in the spread of pathogens, some of which are zoonotic (from animals to humans), such as avian influenza and West Nile viruses. Individual measures of avian health may include physical measurements (e.g., body mass, wing length), pathogen infection status, the host-associated microbial community (the microbiome), and behavior (e.g., movement, migratory status). In particular, the microbiome is known to play diverse functional roles in individuals, including in immune function, growth, and physiology, however little is known about the relationships between the microbiome, pathogen infection, and fitness in wild birds. Here, we sought to evaluate indicators of avian health and the factors that drive them by (1) defining the “core” microbiome of mallard ducks (Anas platyrhynchos), (2) demonstrating the utility of microbiome data for pathogen detection in barn swallows (Hirundo rustica), (3) identifying predictors of parasite infection intensity and relationships with the microbiome in Maine waterfowl, and (4) examining whether trait variation (plumage coloration) predicts potential indicators of avian health (pathogen infection, microbiome, movement), and whether these health indicators affect reproductive success in barn owls (Tyto alba). We collected cloacal swabs from multiple wild bird species to characterize the cloacal bacterial microbiome through 16S rRNA sequencing. We also collected biological samples for the detection and/or quantification of pathogen infections: a cloacal swab in nutrient broth for Salmonella (barn swallows) and whole blood for avian haemosporidian parasite (all others). We recorded host ecological data (all species), as well as movement and/or reproductive data (barn owls only) and conducted statistical analyses to identify potential drivers of pathogen infection, microbiome diversity and composition, movement and/or fitness. We found that although six taxa were identified as part of the core cloacal microbiome of mallard ducks, they were not universally prominent across three represented flyways (Obj. 1). Rather, sampling location was found to significantly influence the bacterial microbiome alpha diversity (Chao1; χ2 = 71.218, p = 3.43e-16) of mallards. We also detected Salmonella in 23.1% (25) barn swallow samples and found a significant relationship between the presence of Salmonella and microbiome alpha diversity in swallows (Obj. 2). Location was the primary driver for avian haemosporidian parasite infection intensity in Maine waterfowl, followed by age (Obj. 3). While we found no consistent relationship between parasite infection and the avian microbiome across duck species, we did observe a significant relationship between parasite infection intensity and microbiome composition (beta diversity) using the weighted UniFrac measure (F = 3.02, p = 0.013). Finally, we found no relationship between plumage coloration and indicators of avian health in barn owls (Obj. 4). However, female owl movement, as reflected by home range area, was inversely related to measures of reproductive success (clutch size and fledge success. Furthermore, microbiome alpha diversity was significantly correlated with Julian laying date, such that individuals with higher microbiome diversity laid their eggs earlier, thereby potentially enhancing their reproductive potential. Collectively, this thesis evaluates multiple indicators of avian health, including the microbiome diversity, parasite infections, and movement ecology, and provides valuable insight into the ecological drivers and dynamics of host-microbe interactions.

Download

Share