Presentation Title

Evolutionary Association Between Ultraviolet Light, Migration Distance and Non-breeding Latitude and Secondary Moults in North American and European Migratory Passerines

Format of Presentation

Poster to be presented the Friday of the conference

Abstract

Most migratory birds moult after breeding, replacing worn-out feathers from the previous season with new feathers, just prior to beginning their migratory journey south to the tropics. However, some species of migratory birds undergo a second moult on their overwintering grounds, replacing some, or all, of their feathers. Not all migratory birds undergo this prealternate moult and the evolutionary drivers of this behaviour remain unclear, but one potential driver of this strategy could be disproportionately high amounts of feather wear in species that undergo a second moult. The three main sources of wear I examined were ultra-violet (UV) radiation, migration distance, and migratory latitude. Birds exposed to longer day lengths throughout the winter due to their wintering location are exposed to a higher amount of UV radiation. Because migration is an intensive process requiring maneuvering harsh terrain and variable weather conditions, longer migration distances may lead to a higher amount of wear. Finally, the latitude at which birds overwinter may affect the amount of wear on their feathers through habitat or environmental conditions. Using a phylogenetic logistic regression to control for shared ancestry, I found that species undergoing a longer migration, wintering at more southern latitudes, and those experiencing longer and more variable day lengths all showed an evolutionary association with prealternate moult. In other words, my results suggest that high feather wear experienced by some migratory passerines drove the evolution of a secondary moult.

Department

Biological Sciences

Faculty Advisor

Matt Reudink

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Evolutionary Association Between Ultraviolet Light, Migration Distance and Non-breeding Latitude and Secondary Moults in North American and European Migratory Passerines

Most migratory birds moult after breeding, replacing worn-out feathers from the previous season with new feathers, just prior to beginning their migratory journey south to the tropics. However, some species of migratory birds undergo a second moult on their overwintering grounds, replacing some, or all, of their feathers. Not all migratory birds undergo this prealternate moult and the evolutionary drivers of this behaviour remain unclear, but one potential driver of this strategy could be disproportionately high amounts of feather wear in species that undergo a second moult. The three main sources of wear I examined were ultra-violet (UV) radiation, migration distance, and migratory latitude. Birds exposed to longer day lengths throughout the winter due to their wintering location are exposed to a higher amount of UV radiation. Because migration is an intensive process requiring maneuvering harsh terrain and variable weather conditions, longer migration distances may lead to a higher amount of wear. Finally, the latitude at which birds overwinter may affect the amount of wear on their feathers through habitat or environmental conditions. Using a phylogenetic logistic regression to control for shared ancestry, I found that species undergoing a longer migration, wintering at more southern latitudes, and those experiencing longer and more variable day lengths all showed an evolutionary association with prealternate moult. In other words, my results suggest that high feather wear experienced by some migratory passerines drove the evolution of a secondary moult.