Birds Remember Locations of Food Caches

Most Jays Have Exceptional Memory for Food Locations

Sep 15, 2008

Some birds can hide thousands of seeds and go right to them five or six months later. This is important because their survival may depend on finding the seeds again.

Some people are forever looking for their keys, eyeglasses, cell phones, TV remotes, and many other objects. It seems a foible of human nature that the smartest organism to ever live on Earth has such a problem remembering where an object was last placed. Who would think that a mere bird would perform better than a human? But they can remember where they stored food better than all other animals because their lives often depend on it.

What Kinds of Birds Store Food?

A wide range of songbirds cache (hoard) food. Chickadees and tits (Parus spp.) and nuthatches (Sitta spp.) visit bird feeders, fill their throat pouches with seeds (much as a chipmunk, Tamias sp., would fill its cheek pouches), fly away, and hide them in bark crevices, the ground, or under stones or logs. Woodpeckers visit shrubs and trees containing berries (poison ivy, bittersweet, juniper) or nuts (beech, oak), transport the seeds (sometmes several miles), and place them in bark crevices or holes they have previously drilled in a tree trunk or post. Acorn woodpeckers use communal posts year after year. Shrikes (Laniius spp.) kill grasshoppers, small mice, or other birds and impale them on the thorns of hawthorn (Crataegus spp,) trees for temporary storage.

Some Birds Can Remember Thousands of Caches

Many jay species cache several hundred seeds when food is plentiful. But the gold medal of caching goes to the jay family. Most jays store several thousand acorns, sunflower seeds, and pine nuts for later retrieval. Within the jays, there is a hierarchy of storage and retrieval abilities:

While most jays can carry a dozen or more small acorns in their throat pouches, nutcrackers will carry 100 or more pine nuts at a time in their even larger pouches. The seeds are usually buried in a hole in the ground that the jay digs just before depositing the seeds. One to ten seeds are placed in the hole and the caches are scattered over a large area. The hole is covered over and then a leaf, stone, twig, or scrap of litter is placed over the hole to camouflage it. The bird flies away and will not return to the hole until it is ready to retrieve the seeds. Sometimes a bird of another species or a squirrel will observe the jay bury the seeds and retrieve it as soon as the jay walks or flies away – sometimes while the jay is still nearby. But jays rarely steal from other jays - even when they observe the seeds being buried.

How Birds Remember Cache Locations

Multiple experiments performed with captive birds in Russell Balda's lab at Northern Arizona University have demonstrated they can remember caching locations by noting the positions of stones, shrubs, and other landmarks in the area. If the landmarks are shifted, the birds err in their retrieval attempts by searching in the correct locations according to the position of the landmarks, but not the actual locations of the seeds.

In the wild, nutcrackers will fly directly to a cache location even if the ground, trees, and shrubs are covered with several feet of snow, dig down to the precise location of the seeds, and retrieve them. Even first-year birds that had not visited the area of the seeds before caching them are able to return to the area, locate their caches, and dig directly to the seeds.

Clark's Nutcracker Has a Mutualistic Relationship with Whitebark Pine

Ronald Lanner, who has studied Clark's nutcracker for several decades, has documented adaptations that both the nutcrackers and the pines developed while forging a mutualistic relationship between them. He hypothesizes that the nutcracker's bill size, throat pouch, and memory abilities evolved as a result of the harsh winter conditions in this species' montain habitat. His comparison of the seed size and structure in pines whose seeds are planted by birds and those whose seeds are destroyed by birds indicate that the differences between these seeds are adaptations that favor, on the one hand, transport by the birds; and on the other, transport by wind.

The discussion of Clark's nutcracker is based on the book: Made for Each Other: A Symbiosis of Birds and Pines. Ronald M. Lanner. 1996. Oxford University Press, New York.

The copyright of the article Birds Remember Locations of Food Caches in Wild Birds is owned by Albert Burchsted. Permission to republish Birds Remember Locations of Food Caches in print or online must be granted by the author in writing.