It is during the autumn and early winter months that Jays are at their most conspicuous, the numbers present often increased by the arrival of birds from further afield. Although a wary species, individual jays may become surprisingly approachable when they visit gardens to take bird table fare or cache acorns.
The mighty Oak
Acorns are the staple food for Jays during the autumn months and individual birds may travel some distance to find a supply. Birds may be seen collecting the acorns, with three or four carried in an adapted gullet and one more held in the bill. The acorns are usually taken away from the immediate vicinity of the oak to be cached elsewhere, typically in a hole that the Jay has made in the ground with its beak.
The close association between the Jay and oak trees is reflected in the scientific name given to this colourful member of the crow family. The word ‘glandarius’, which forms the species component of the bird’s scientific name, is derived from the Latin word for acorn. An individual Jay may hoard as many as 3,000 acorns and these will provide the bird with food over the coming months. Jays have an amazing ability to recall the location of their hoarded acorns, although it is known that (during the summer) they can use the presence of a newly germinated sapling to reveal the presence of an acorn at its base.
Ups and Downs
The numbers of Jays present here during the autumn and winter is influenced by acorn crops over a wider area. As with other trees, the crop of acorns is an unpredictable resource and acorn abundance may vary considerably between years. When crops elsewhere have been poor, substantial numbers of Jays are thought to arrive here from northern and eastern Europe, although this has yet to be confirmed by bird ringing – probably because so few Jays are ringed each year.
Our breeding population of Jays is largely sedentary in its habits and numbers have been generally stable over the past 40 or so years. The long term pattern hides some short term variation, with a pronounced fall in the CBC/BBS trend during the late 1980s; the index recovered from the late 1990s and is now back at about the level seen in the 1970s.
The association with oak and deciduous woodland drives the pattern of abundance revealed by Bird Atlas 2007-11. Both breeding season and winter abundance are at their highest levels in the south and east of England, with the New Forest and the Surrey Weald particular strongholds. Avoidance of upland landscapes is also evident and the species is also far less common in the open arable landscapes of the Fens and north into Lincolnshire. The atlas data also reveal an increase in the bird’s range since the 1968-72 Breeding Atlas, with parts of Scotland and Ireland newly occupied.
A bit of a loner
Unlike many other members of the crow family, Jays do not form large flocks. Instead, small groups may be encountered in spring and these are thought to be unpaired birds looking for a mate. Even the two members of an established pair seem to spend relatively little time together, although they will work together to defend their breeding territory and both birds construct the nest and feed their young. The nest of a Jay is usually placed fairly high in a tree and consists of a scruffy base of twigs onto which is placed a more delicate cup of rootlets and finer twigs. BTO Nest Recorders fortunate enough to have seen a Jay nest say it looks like a giant version of the more commonly encountered Bullfinch nest.
Jays are resourceful birds and will take a wide range of foods. They are perhaps best described as opportunists, taking foods that happen to be abundant. In addition to acorns, they will take beetles and caterpillars and they will also raid the nests of smaller birds to take eggs and young. Jays sometimes take food put out in gardens, particularly when they have hungry young in the nest to feed, something revealed by the weekly observations of BTO Garden BirdWatch participants.
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