Birds can remember what, where, and when.

Struggling with the temporal cognitive challenge posed by leftovers going bad in the fridge, people may not be so superior to other animals after all.

Scrub jays can remember when they cached a particular kind of food in a particular place, report Nicola S. Clayton of the University of California, Davis and Anthony Dickinson of the University of Cambridge in England. The birds tend not to bother recovering a perishable treat stored long enough to have rotted.

This pickiness "has many of the hallmarks of episodic memory," Clayton says. That's the kind of memory that lets a person mentally time-travel back to recall the suite of details of a particular experience, like stashing a casserole behind the milk. Are the scrub jays doing an avian version of the same thing?

"I can't ask them," Clayton laments. However, when she and Dickinson focus on bird behaviors, they find that the cache-recovery pattern of scrub jays fulfills the "`what,' `where,' and `when' criteria for episodic recall." The jay study "provides, to our knowledge, the first conclusive behavioural evidence of episodic-like memory in animals other than humans," the researchers say in the Sept. 17 Nature.

That birds have keen abilities for recovering food does not surprise Clayton because their skill has "life-or-death" consequences. For instance, chickadees that tough out the winter in Siberia must find many of the half-million seeds they hide each year. In the worst of the season, the chickadees have only about 3 hours of daylight for foraging.

Previous work has indicated that birds find their stashes not by smelling hidden food but by remembering the location. In laboratory tests, birds called Clark's nutcrackers have recalled where they buried something 9 months earlier. Birds also remember what they've stored. Black-capped chickadees, for example, retrieve favorite foods first.

To test for memories of specific events and their timing, Clayton and Dickinson let some scrub jays discover that wax-moth larvae, a favorite food, will rot after a few days. The researchers then gave the birds fresh larvae to bury in ice-cube trays full of sand. After five days, the jays cached peanuts.

When these birds later had a chance to harvest their treats, they mostly probed for the peanuts and ignored the larvae locations. Birds that did not know about the decay, however, spent more effort looking for the larvae than the peanuts.

Larry R. Squire, who studies primate memory at the University of California, San Diego, says he was already convinced that monkeys and rats could recall what happened when and where. "I think it's exciting that the bird work is so consistent with the mammals," he says.

The scrub jay study is more convincing than the work on mammals, says Endel Tulving of the Rotman Research Institute of Baycrest Centre in Toronto, a founder of episodic-memory theory, in the mammal demonstrations to date, "there are other ways that the animals could have solved the problems," he cautions.

Clayton's jay work strikes Tulving as "inventive and very clever." He says, "I think that she's got something there."