Stash the cache
THIS time of year is hard for birds, with cold temperatures and little time to find sufficient food. This is when putting out food can make a real difference. Birds at a feeder often feed while perching there, cracking open seed after seed or chipping away at peanuts. Others grab and fly, snatching a piece and disappearing only to return again very quickly for more.
These birds are ‘caching’ – taking advantage of a ready (and readily refilled) food source by taking as much as they can and storing it away. One benefit of this is that the stored food is available at any time, so birds which successfully hide food don’t need a large supply of body fat, or spend a long time searching for food, which is better for avoiding predators.
A wide range of birds hide food in winter, including tits and chickadees, nuthatches, jays, nutcrackers and crows, woodpeckers, shrikes (impaled in a larder), falcons and even owls. Chickadees can hide as many as 80,000 seeds for retrieval, which they find successfully, while a single
Jay can store up to 3,000 in a month and a study of the species in Germany estimated that 250 Jays removed 3,000 kg of acorns in a mere 20 days! Pygmy owls have been known to hide up to 200 items, mainly small mammals
Tits and nuthatches tend to take a single seed or nut and fly off with it, storing it in a suitable place such as a crack in a tree or under some peeling bark. Jays are able to carry off several nuts at a time, having a distendable pouch in front of the tongue, and will usually bury them all underground in one stash.
By using many different locations to store their food – known as scatter hoarding – birds reduce the chance of food being found by others. Great Tits are known to watch Coal Tits to learn where their hoards are. Jays in North America hide their food in shady areas or behind large objects to screen their precise location from others that might be watching.
Research in North America showed that birds with the best spatial memories are more likely to survive their first winter and that females that mate with males with good memories, produce bigger broods. Birds which store food usually have an especially well-developed hippocampus which gives them a better memory, and their brains actually increase in size in the autumn to prepare for the winter, decreasing again in spring.
Tits and nuthatches are known to remember locations for only a few weeks, while corvids can remember where things have been placed for many months. To relocate their food stores birds will use landmarks such as rocks and trees and also a sun compass. Some species rely less on their memory and simply place food stores throughout their territory and then relocate it by searching at a later date. Chris Harbard