Prolefeed Studios recently received a grant from the Wisconsin Society for Ornithology to study the plumage of Black-Capped Chickadees (Poecile atricapillus) under reflected sunlight in the near ultraviolet spectrum (300-400 nanometers). Many birds and insects can see a wider range of electromagnetic radiation than humans can, including the 300-400nm band. Several researchers have theorized that Chickadees, which appear uniformly black and grey to the human eye, might exhibit more distinctive markings under UV illumination.
Using a specially built lens and an astronomical “Venus” filter, we were able to restrict the range of light entering a video camera to the ultraviolet portion of the spectrum. We then set up two cameras side-by-side, one sensitive only to UV light, the other unfiltered and sensitive to the visible spectrum, and videotaped birds on a bird feeder. By mapping the UV image to blue and then superimposing the UV and visible light images, we were able to create a false color video that simulates how Chickadees might look to other birds. Preliminary results are shown below.
Areas that reflect a high degree of UV light are shown in blue. These distinctive markings on the side of the bird’s cheeks and back may help with identifying mates. The next step in this project will be to try to videotape male and female chickadees to see if, as expected, there are marked differences in the UV markings of each gender. This may have to wait until fall when the birds form flocks, since nesting pairs are rarely seen together on bird feeders in the spring.
Some interesting discussions about this project on a couple of other discussion boards: