It is actually very difficult to distinguish
experimentally between an animal that is simply
using landmarks and one that is using a cognitive
map. The best evidence for a cognitive map comes
from research on the family of birds that includes
jays, crows, and nutcrackers. Many of these birds
store food in caches. A single bird may store nuts in
thousands of caches that may be widely dispersed.
The bird not only relocates each cache, but also
keeps track of food quality, avoiding caches in
which the food was relatively perishable and would
have decayed. ----