Western Grebes (Aechmophorus occidentalis) are a colonial nesting, piscivorous water bird. Their colonies can range from hundreds to thousands of individuals. The purpose of my investigation was to quantify species richness and species abundance at the grebe colony in comparison to a number of non-colony sites. The nesting period presents a challenge in that adult grebes must choose a location that provides protection as well as access to foraging grounds for a large number of individuals. Hence, the colony site should not only support grebes, but also be attractive habitat for other birds that share similar habitat requirements as the Western Grebe. It follows that the grebe colony would have higher species richness and species abundance than the other study sites. I conducted my investigation at Cascade Reservoir at Cascade, Idaho. I performed point counts at six different sites around Cascade Reservoir: the grebe colony, three natural sites, and two developed sites. I performed the point counts between June 19 – July 10 of 2018. I then calculated both Simpson’s and Shannon-Wiener indices for each site.
Results/Conclusions
Based on the points counts I calculated a Shannon-Wiener index of 1.63 for the grebe colony and a Simpson’s index of 0.71 These were higher than the developed site (mean Shannon index 1.39 and the mean Simpson index .68) and lower than the natural sites (mean Shannon 1.81, mean Simpson index .81). Although the colony scored lower than the natural sites, it did have both higher number of species (n=22) and higher number of individuals (n=103). The data suggests that the grebe colony does present attractive habitat for a multitude of other avian species. Western Grebes can serve as an umbrella species for other birds that rely on similar habitats. Future investigations should quantify various habitat metrics such as water quality and vegetation at the colony to target conservation efforts.