This post was contributed by Allison Walker, Mika Kirkhus, Rielle Hoeg, and Dave Shutler, authors of a recent paper in The Wilson Journal of Ornithology about using eDNA to identify raptor pellets.

In the field, bird researchers regularly encounter raptor pellets, which are regurgitated clumps of indigestible animal material such as fur, feather, and bones. However, where multiple species of similar-sized raptors occur, it can be hard to tell which species produced a pellet based on the pellet’s appearance alone. After field seasons spent on two Nova Scotian islands collecting raptor pellets as part of a study on predation on seabirds, one sample of pellets raised our eyebrows. The pellets we collected from an island known to host Great Horned Owls were small, about half the size of a computer mouse; those we collected from another island were huge — easily four times the size. We speculated about what could have disgorged such a monstrosity. Could it have been a Snowy Owl? Probably not, given the similar size of the two owls. An eagle? Seemed more likely, but how could we know for sure? Thus, we became interested in developing a way to identify bird species producing pellets based on residual environmental DNA (eDNA). We suspected DNA in pellets could come from a bird’s digestive tract cells, leaving behind a genetic signature in the field telling us “Who puked?”
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