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Seabirds are a highly endangered group of vertebrates; they are more threatened than any other group of bird. However, the Common Murre is one species that is showing an increasing population trend; I found that Common Murres have shown a significant increase in δ15N since 1994, in contrast to the threatened Marbled Murrelet, which has a similar biology but has shown decreasing δ15 N values that typically correlate with declining population size. This is potentially due to sexual dimorphism that allows for the Common Murre to fill a larger niche. While I found no statistical difference between male and female isotope values, further evaluation could be used to see if this larger niche is a result of other factors. Stable isotope analysis of δ13C and δ15N is one way to investigate these population trends since they are capable of showing foraging habit (inshore vs. offshore) along with trophic level. Unfortunately, as of now, there is no standardized way to sample feathers for isotope analysis, and it has been shown that different locations on the feather show different isotope values which correlate with the melanin concentration of the location. I found a consistent offset in δ13C between the tip and base of the feathers sampled. This offset could lead to slight differences in interpretation of the foraging strategy being used by the bird. Since seabirds are in such a threatened position, it is important to have a paramount understanding of their habits possible to ensure the best conservation efforts are being utilized.
Gosciak, Kimberly, "Stable Isotopes in Seabirds" (2015). Williams Honors College, Honors Research Projects. 155.