Hide the hazelnuts, the Nutcracker’s are invading…

They came from the east. Nobody sent an invitation, nobody checked their papers, and every single one of them arrived with their cheeks full of illicit snacks. Yes, we are experiencing an irruption of Nutcrackers, and by all accounts both sub-species are on the move South. Normal birds are wary of humans. Nutcrackers have read about this and decided it doesn't apply to them. They perch on the very top of the tallest, most visible tree. Approach to within a few metres and the bird will look at you with an expression of mild disappointment, as if you were the one who had wandered into its territory.

The Nutcracker, a chocolate-brown, white-flecked corvid, about 33 cm long, with a dark cap, a white-tipped tail and a bright white undertail. It flies with a woodpecker-like undulating flight and gives a dry, rasping krraah. The Nutcracker specialises in conifer seeds and hazelnuts, carrying them in a pouch under the tongue and burying thousands in scattered caches. It relocates them months later, even under snow. The forgotten ones become new Siberian and Arolla pines. The Siberian birds (the slender-billed form, macrorhynchos) head west when the taiga's pine seed crop fails. They arrive in southern Scandinavia and beyond in autumn.

Why irruptions happen? Irruptions follow a boom-then-bust cycle. A good seed year in the taiga produces strong breeding success and a large population. A following crop failure of Siberian pine (and sometimes hazel) then pushes many birds, especially juveniles, south and west in late summer and autumn. They cross Finland, the Baltics and southern Scandinavia, and the largest waves reach Germany, the Netherlands and Britain. Major irruptions come every so often rather than on a fixed schedule. A bonus for me as a photographer, often these irruptive birds are tame and easy to watch. They show up in gardens, parks and woodland edges, feeding on hazelnuts, acorns and walnuts, and sometimes visiting bird tables. Many are forced to move on once natural food runs out, though some overwinter.

Welcome to southern Scandinavia, Nutcracker, you are a welcome guest.