大山雀觅食时使用鸟瞰视野

Birds that hoard（贮藏） food for a rainy day better be sure that there are no great tits around to spy on where they hide their reserve of seeds and nuts. So says Anders Brodin and Utku Urhan of the University of Lund in Sweden, who found that great tits can remember the position of such hideaways up to 24 hours after seeing it cached. Interestingly, even though great tits share this mental ability with well-known hoarders such as crows and jays, they do not store up food themselves. The findings appear in Springer's journal Behavioral Ecology and Sociobiology. Observations were conducted in a laboratory especially designed for bird experiments. Caged great tits (Parus major) were first allowed to observe where marsh tits (Poecile palustris) stored away sunflower seeds. After a retention interval of either one or 24 hours, the birds were then allowed to go in search of these caches. The great tits did this most accurately after one hour, while they were just slightly less accurate in memorizing the hideaways after 24 hours.

In nature it is very useful to be able to observe others' cache and to memorize its location so that it can be recovered at a later stage. This elaborate strategy requires memory storage over an extended time. This skill has previously only been demonstrated in some species of corvids, such as the Mexican jay and Clark's nutcracker. The current Swedish study is the first to show that members of the Paridae family, which include tits, chickadees（山雀） and titmice, have the same observational spatial learning and memorizing ability.

Brodin and Urhan write that they are not surprised that great tits have the cognitive capacity to do observational learning, given their innovative feeding behavior in general. Previous research has shown that they could observe and learn complex foraging behavior not only from other birds of the same species but also from blue and marsh tits.

What Brodin and Urhan did find surprising is that this species is not itself a food hoarder, and may therefore not have the special memory adaptations in the brain that is possessed by specialized food hoarders. They believe that an observing pilferer uses different memorizing techniques than hoarders, and has some understanding of allocentric space that allows them to understand the position of the cache even if it is not in direct view.

"The ability of observational memorization could be more important for non-hoarders than for hoarders, as this could increase their chances of survival especially when foraging conditions are bad," says Brodin. "For example, after a blizzard, the access to stored food may be the difference between life and death."