"a team of biologists from the University of Utah have once again turned to pigeons to demonstrate evolution in action"

Atlantic:

In a simple experiment, Sarah Bush and Scott Villa placed feather-eating lice on differently colored pigeons, and left them there to breed and evolve—for four years. Over that time, the insects adapted to better match the color of their hosts, which made them harder to spot and pluck off.

...

these changes only occurred if the pigeons could preen themselves. Bush stopped half the birds from doing so by fitting them with poultry bits—plastic clip-ons that prevented them from closing the very tips of their beaks. On those birds, the lice suffered no risk of removal, and their colors stayed the same.

*Previously: "The Wild Experiment That Showed Evolution in Real Time"