https://phys.org/news/2018-07-golden-crowned-sparrows-false-crown-strangers.html

"To show that birds are using badges of status, you have to pit birds against each other that have never met to make sure they do not have prior information about fighting ability," explained Bruce Lyon, professor of ecology and evolutionary biology at UC Santa Cruz.

Lyon's lab has now been studying the Arboretum's golden-crowned sparrows for 15 years. The plumage studies have been led by Alexis Chaine, a former graduate student in the lab who is now at the National Center for Scientific Research (CNRS) station in Moulis, France.