In late summer, Clark's Nutcrackers harvest seeds of Pinyon Pines. They stuff the seeds into pouches below their tongues, and then may fly several miles and bury the seeds. A single nutcracker may bury as many as 33,000 Pinyon Pine seeds in groups, or caches (pronounced CASH-es), of four of five seeds each. When winter comes and food is scarce, the bird returns to its thousands of caches and eats its seeds.
Earlier it was thought that probably nutcrackers remembered only the general area where their seeds were stored, or that perhaps they could smell the seeds. Now after many ingenious experiments, the truth is known. When it comes to remembering where their food is stored, nutcrackers have amazing memories. Their memories are not faultless, but nutcrackers are surely more gifted for this single cache-remembering task than average humans. If you hid seed in five or six thousand tiny holes in the ground scattered over a mountain slope, in several months' time could you remember where most of them were?
In the paragraph above, the phrase "for this single cache-remembering task" is important to notice. When we speak of a bird's amazing cache-finding memory, we're definitely not saying that the bird is "smart." It's simply that finding its food caches in winter is extremely important to the Clark's Nutcracker, so its brain has evolved to be wonderfully developed for the specific task of keeping track of exactly where it caches its thousands of seeds.