This video is a great example of some fascinating evolutionary biology. Illinois Natural History Survey ornithologist Kevin Johnson describes his research on the history of feather lice. Anyone who works with birds knows they are lousy–as in, usually covered in lice.
But how did all those lice evolve? Did they share a common louse ancestor, and then diverge as their bird hosts diverged? Bird winglice from a parrot look a lot like bird wing lice on a duck–but those are very different and unrelated hosts. What does that tell us about the history of lice?
You can read the paper this video is based on here:
Johnson, K.P., Shreve, S.M. & Smith, V.S. (2012). Repeated adaptive divergence of microhabitat specialization in avian feather lice, BMC Biology, 10 (1) DOI: 10.1186/1741-7007-10-52
(Looking for a text transcript of the video; you can get most of the content text here)