How crows cache food Most members of the crow family that have been studied in detail in the wild have been seen to hide food. In captivity, many ravens, magpies, and jays appear to have the compulsion to hide food. Often the food is carried inside the throat of the bird so it is only when the bird is seen to regurgitate or when the food caches are discovered that the extent of food hiding becomes clear.
Food-hiding behavior is usually not seen when the food consists of such small, well-hidden, living items as insects or earthworms. However, when a surplus of bread is supplied to wild jays or crows they quickly begin to hide away supplies. They typically use small holes in the ground, under debris or vegetation, but sites above ground entrees or buildings may also be used. Deliberate effort is usually made to cover the hidden food by raking loose material on top of it, or by walking a short distance to find a stone or another object to place on top.
Several instances have been reported of very hungry ravens and crows, when suddenly faced with an abundance of food, taking the trouble to hide a large quantity before beginning to eat. However, the extent to which food is deliberately stored for later use varies widely between species. Where there are no seasons of major shortage the hiding and later recovery of food are on a small scale, for example with magpies and jackdaws in England. Other species use
Stored reserves of food to allow survival through harsh winter conditions when only scanty food supplies remain available.
The Gray jay inhabits forests of spruce and other conifers over large areas of northern Canada. During the winter, food supplies are very scarce in these forests and the thick and extensive snow cover would prevent the jays from recovering food hidden in the ground. Instead, spruce seeds and other foods are stored in the foliage of the conifers and stuck to the leaves with saliva. For this purpose, the Cray jay has evolved especially large salivary glands.
Food hiding may serve two functions in addition to, or instead of, the provision of food supply during periods of shortage. One suggestion was that the extensive transport and surface burial of acorns by jays and of hazel-nuts by nutcrackers was aimed at the spreading and perpetuation of these trees.
The second suggestion was that the Blue jay may carry and hide food to remove surplus food from its territory. This was argued to have the effect of discouraging other Blue jays from trespassing in search of food, and hence perhaps competing for food later when it may be scarce. Despite these possible explanations, several studies have suggested that at least some members of the crow family derive a significant part of their diet from stored reserves during a season of food shortage. Hence it seems likely that this is the main function of food hiding.
The crows’ memory for the whereabouts of hidden food is good. European nutcrackers spend much of the fall hiding hazelnuts or pine seeds in holes in the ground, often carrying them for over a kilometer. During the winter, the diet of the nutcrackers includes a high proportion of this stored food, and they can excavate food from beneath 20 cm (8in) or more of snow covers. There are records of nutcrackers feeding hazelnuts to their nestlings in the late spring and these nuts were presumably hidden during the previous fall. Nonetheless, some of the hidden nuts and pine seeds are not recovered and these may germinate, having been both dispersed and “planted” by the nutcrackers.
By comparison with the European nut-cracker, a study of jays in Holland suggested they were less efficient at recovering acorns, relying in part on the development of growing shoot to reveal the hiding place. However, jays also recover many acorns before they germinate, and there is one instance recorded of them digging through snow to find them.
Social crows such as the rook may have difficulty in hiding food where it will not be discovered by other members of the flock. There are several observations of the meteor and other birds of the flock watching food being hidden and then quickly trying to find it. In these instances, the bird often appears to have difficulty locating the exact spot. Whereas the bird that hid the food may be immediately successful in recovering it.
See more: Ravens