This study had a hawk silhouette fly above roosters while they were alone, in the presence of another rooster, or in front of a mirror. Roosters typically give a warning call to other chickens if they see a predator. The idea was to test whether roosters responded to a predator as if their reflection was another chicken they needed to warn, because this behavior would indicate a lack of mirror self-recognition. Roosters did not warn their reflection, suggesting that they did not treat the reflection the same as they treated a separate rooster.