Siskins are heading south. Many have been seen by those early-rising birdwatchers who go to the high hilltops and watch migrating birds fly past at dawn. They have also been arriving in flocks in the alder trees beside rivers in southern England.

These brilliant little green-and-gold finches nest mainly in Scotland and the North in firs and pines, though since the Second World War they have also colonised some of the new conifer forests in the South. Many more now fly into Britain from the Continent for the winter.

When they feed in the alders, siskins are not always easy to see. They hang upside down, drawing seeds out of the alder cones with their long, narrow beaks, and among the tangle of cones, long purple catkins and green leaves, which linger late on alders, their silhouettes are easily lost to sight, especially when the vegetation is shaking in the wind.

Siskins can often be detected by their calls, which are thin, sweet notes or faint twanging sounds. However, they sometimes display themselves in a striking way. A strange collective panic seizes them, and they rush out of the tree in a tight-knit flock, together making a mosaic of tinkling sound, like the aural equivalent of a shimmer of sunlight.

They wheel rapidly around, then come plunging back into the tree.

One winter I found a large flock in a very different situation. A field of flax had been harvested, and numerous siskins were feeding on the oily seeds that had been left behind in the thin brown stalks of stubble. Sharing this windfall were chaffinches and yellowhammers, and those siskins that had eaten their fill were sitting in trees along the field’s edge. All were facing the wintry sun to warm their white stomachs, with their gold wing-bars gleaming.

Siskins have also become garden birds. The first one ever recorded at a bird table was in 1963, which was a hard winter. Since then they have become regular visitors to garden peanut feeders. So it is just the moment to put out one of those, and hope.