Visual Analysis & Structural Coloration

This past week, field work proceeded as usual. We conducted assays, nest box checks, banded birds, and collected feather samples. I also begun visual analysis of the feather samples! Visual analysis will be used to get more information on how CORT levels impact individual condition, and will be overseen by Casey McLaughlin.

I begun the visual analysis process by measuring and weighing every feather that had been collected from the field sites thus far. Since this was the first time I got to spend in depth time looking at the feathers, it was really interesting to see the amount of individual variation in size, shape, coloration, growth bars, and overall condition.

One aspect of (blue) bluebird feathers that makes visual analysis particularly important is how they get their color. Bluebird feathers appear blue due to structural coloration. Unlike coloration caused by pigments, such as melanin, structural coloration is caused by the actual structure of the feather reflecting light in a certain way. This causes the feathers to look different at different angles, as demonstrated in the video posted below. Because it can be taxing for individuals to produce these elaborate structures, they tend to be accurate indicators of individual wellbeing. Individuals in poor condition, such as those experiencing high stress levels, may have imperfect structure that results in duller coloration. The next step of visual analysis will be conduct UV vis analysis with a spectrometer. This will give us more information on the brightness, hue, and chroma of the feather.


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