Faculty Mentor(s)

Dr. Kelly Ronald, Biology

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Visual signal propagation through the environment can be influenced by many factors, including the visual background. For example, normally camouflaged animals can appear quite salient when the environmental substrate is changed. Deer can alter this visual background by consuming the forest understory; ultimately this can have implications for species that use visual signals to attract a mate or defend a territory. We are interested in studying how deer browsing affects the chromatic contrast (i.e., how much an animal stands out from the background for a given receiver) using an avian model system. Brown headed cowbirds (Molothrus ater) and wild turkeys (Meleagris gallopavo) inhabitat the forest understory that is subject to deer browsing . We used published data on cone photoreceptor sensitivity of these species to model chromatic contrast of avian plumage against forest backgrounds. We also used a general avian eye model to investigate the chromatic contrast of plumage colors across the visible light spectrum, from the red of Northern cardinals (Cardinalis cardinalis) to the blue of blue jays (Cyanocitta cristata). To calculate chromatic contrast we used spectroscopy measurements from (1) the forest understory as the visual background, (2) plumage reflectance and (3) irradiance measures. We modeled this in both deciduous and mixed forest types and at different heights from the forest floor (i.e., low and high). We predicted that areas that allow deer will cause birds to be more conspicuous. Additionally, we expected the effects of deer browsing to be greater at lower heights because of the increased foraging and disturbance of the forest floor. In the future, we will examine if achromatic contrast (i.e., contrast based on brightness cues) are affected similarly. Taken together, this work will shed light on how different environments can drastically affect the way birds communicate.


Research reported in this publication was supported in part by funding provided by the National Aeronautics and Space Administration (NASA), under award number 80NSSC20M0124, Michigan Space Grant Consortium and the Brookstra Faculty Development Fund.

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