Master of Science
Morbey, Yolanda E.
Guglielmo, Christopher G.
Millions of birds die annually in North America by colliding with windows. I investigated differential vulnerability to window collision among migratory songbird species using long-term citizen science datasets from two bird banding stations and the fatal light awareness program. I used negative binomial regressions to model species-specific catch ratios, a mixed-effects negative binomial regression to model trophic guild-specific catch ratios and mixed-effects logistic regressions to model the odds of catching different age classes. Species-specific vulnerability varied significantly. Blue-headed Vireos, Yellow-rumped Warblers and Ruby-crowned Kinglets were least vulnerable, while Ovenbirds, Common Yellowthroats, Fox Sparrows and Bay-breasted Warblers were most vulnerable. Foraging height influenced vulnerability with ground foragers being most vulnerable. The effect of age varied across species, with only some species showing significant effects. This study contributes to the growing foundation that is required for future studies to investigate why these factors influence vulnerability and how to minimize future collision mortality.
Summary for Lay Audience
There are many songbirds in North America that migrate in the fall to wintering grounds as far south as South America. During this annual fall migration, millions of birds die by colliding with windows. For my thesis, I investigated if some species of songbirds die from window collisions during fall migration more than others. I investigated this differential vulnerability using long-term datasets from three citizen science projects. Two of the datasets were from bird banding stations that collect regional bird abundance data (Tommy Thompson Park, Toronto, ON and Long Point Bird Observatory, Long Point, ON) and one was from the fatal light awareness program that collects bird-window collision data (FLAP, Toronto, ON). I used a variety of statistical models to compare the number of birds caught, or collected, by each citizen science program. These comparisons determined if different species of songbirds collided with windows at the same rate (equal vulnerability), or if they collided at different rates (differential vulnerability). Using this method, I investigated differential vulnerability in 36 species, as well as across 3 trophic guilds and 2 age classes. I found that species varied significantly in their relative vulnerabilities, and that Blue-headed Vireos, Yellow-rumped Warblers and Ruby-crowned Kinglets were least vulnerable, while Ovenbirds, Common Yellowthroats, Fox Sparrows and Bay-breasted Warblers were most vulnerable. Additionally, I found evidence that the trophic guild an individual belong to, specifically the height at which the bird forages, influences vulnerability with ground foragers being most vulnerable. Lastly, I found that the extent that age affects vulnerability varied across species, with only some species showing significant effects. This study contributes to the growing foundation that is required for future studies to investigate why these factors (i.e. species, trophic guild and age) influence vulnerability and how we can minimize future window collision mortality.
Colling, Olivia M., "Differential Vulnerability to Window Collision Mortality Among Migratory Songbird Species" (2019). Electronic Thesis and Dissertation Repository. 6410.