Birds may find way with cognitive map.

No matter where they roam, many animals return regularly to their nesting grounds, food storage sites, or other key locations. However, researchers have yet to determine conclusively whether any of these creatures constructs a mental picture of real-world landmarks, also known as a cognitive map, that guides them to their destinations.

Members of one bird species, the Clark's nutcracker, display a type of geographic insight which suggests that they may indeed consult cognitive maps, according to a report in the Nov. 20 Nature. After learning that they can recover edible seeds at the halfway point between two landmarks that vary in the distance that separates them, Clark's nutcrackers consistently seek out that midpoint in new situations.

"This finding is consistent with the existence of a cognitive map in Clark's nutcrackers, but it's not conclusive," says psychologist Alan C. Kamil of the University of Nebraska in Lincoln, who conducted the investigation with Nebraska colleague Juli E. Jones.

Many animals have shown an ability to reach a desired location on the basis of its distance and direction from a stable landmark, but Clark's nutcrackers navigate according to abstract geometric relationships between pairs of moving landmarks, Kamil and Jones assert.

Clark's nutcrackers avidly store seeds in the wild. A single bird may bury as many as 25,000 seeds in several thousand places during the fall, returning as many as 9 months later to dig up the booty.

In a large observation room, five nutcrackers readily learned to retrieve seeds buried by the scientists halfway between a green pipe and a yellow pipe. During the training, the short, vertical pipes were always oriented along a north-south line, but the distance between them was varied.

In trials featuring five new distances between the pipes, the birds flew to the halfway points, where the researchers had again buried seeds.

The animals strayed slightly from the halfway mark when the landmark orientation was rotated 45 [degrees] from the northsouth line. They veered even farther off course when facing a 90 [degrees] rotation. As the degree of rotation increased, Kamil theorizes, the birds were more apt to take their bearing from a single landmark rather than compare bearings from both landmarks.

Further research is needed to explore whether pigeons and other avian species also exploit geometric links between landmarks as they move about, remarks psychologist Sara J. Shettleworth of the University of Toronto.