Chris Clarke wrote a wonderful little bit of ethological observation as a Facebook status.
Today I watched a raven with a Cheeto being carefully stalked by two California gulls looking for a way to snatch the treat away. The raven hid the Cheeto under a leaf as the gulls watched. The gulls seemingly concluded that the Cheeto was gone and wandered off.
As people pointed out in comments, this neatly shows that gulls don’t have object permanence while ravens do have theory of mind.
(I look forward to an avalanche of Cheeto ads in my future…)