It’s interesting to reflect that until the 19th century, breeding siskins were confined to the northernmost Scottish pinewoods. Even now they’re erratically spread and often no more than wandering winter visitors to this county. This was the perfect place to find them. The Derwent ran under the road bridge as a glimmering black plane then vanished into a skein of alder branches along each bank. Siskins love alder seeds, and even above the river roar I could hear their distinctive “be-Doo” calls. Perhaps the best way to convey the species’ tiny size – it measures approximately 12cm and weighs 12g – is that I could see the birds in the bare alders only when they moved. The flock rotated around the canopy in a random churn, birds pinging bough to bough in search of seeds, so that it was almost impossible to estimate their numbers. Even worse, as I made a tally I could never relocate them the moment they landed, so that the count never proceeded beyond about fifteen-ish. I guessed, therefore, that in total there might be 20. Then they flew sequentially, one after another, to an adjacent alder. I logged the whole thing. There were 56. Needless to say, the tree into which all moved still looked as bare as its predecessor. It was as if they had vanished into the grey winter light. Yet I could hear them and that was more than enough. The odd title “siskin” derives from a German equivalent Erlenzeisig (erlen simply means alder) but the zeisig element was almost certainly taken from an older Czech word čižek. Language fails miserably before siskin sounds but the Middle European name is beautifully onomatopoeic of the song’s prelude. It is a weird invertebrate wheeze that rounds out and swells into a jumbled run of liquid twittering notes. Best of all is when a male delivers the whole thing during an aerial display. He appears little more than a silhouetted blob bounding above the treetops, except that the wingbeats are slow and deep and exaggerated, and his creaking song unfurls among all that cold air like brightly coloured streamers in the hands of a dancer.