From Science:
When it comes to good recollection, elephants get the lion’s share of the glory. But now an animal only slightly larger than an elephant’s toenail is giving the largest land mammal a run for its memory. Hummingbirds can keep a running tab of multiple aspects of their visits to at least eight different flowers over the course of several days, displaying a type of memory once attributed solely to humans.
There’s long been speculation that only people have a memory for unique personal experiences, which is indicative of a sense of self. If future experiments show that hummingbirds can also keep track of the quality or type of nectar, they could challenge the view that only humans have this sense, he says.
More here.