The Impact of Human Disturbance on the Foraging Ecology of Green Herons (Butorides virescens)




Moore, Amanda A.

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As the trend towards urbanization continues, natural areas can become highly urbanized and recreational use of these natural areas might also increase. Waterbirds use areas that are generally subject to elevated levels of human disturbance and consequently are often considered highly susceptible to disturbance. In 2013 and 2014, I assessed the effects of human recreational disturbance on Green Herons (Butorides virescens) through the use of focal observations. I collected behavioral data during 154 observations along the headwaters of the San Marcos River located in Central Texas; the river varies in its degree of human recreational activity and thereby disturbance varied across sites. I built 15 linear regression models to assess the potential influence of human disturbance as well as potential influence of habitat differences between study sites on each of the response variables (4 foraging behaviors and foraging efficiency). Using Akaike’s Information Criterion (AIC) model selection, I found that differences in habitat provided the best explanation for the observed variation in 4 of the 5 response variables measured. These results suggest that Green Heron foraging behavior is not significantly affected by human recreational disturbance but influenced more by differences in habitat. It is possible that the birds have become habituated to disturbance and tolerant of humans and perhaps now only modify their foraging technique in order to maximize their foraging efficiency to suit a specific location. These findings are noteworthy because it is important to distinguish cases where human disturbance impacts a species from cases where it does not. The findings may assist in an ongoing effort to strike a balance between the needs of waterbird species for aquatic resources, and those of humans for recreational use of the same aquatic systems.



Foraging ecology, Green herons, Waterbirds, Human disturbance, Human recreation


Moore, A. A. (2014). <i>The impact of human disturbance on the foraging ecology of green herons (Butorides virescens)</i> (Unpublished thesis). Texas State University, San Marcos, Texas.


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