The arrival of milder weather suddenly made February’s eight days of snow and ice seem like a distant memory, to the extent that a flock of 17 fieldfares loafing in oak trees appeared anachronistic, despite the fact that winter thrushes may be with us for some weeks yet.
Still on the subject of winter thrushes, three times in the past ten days I’ve been cheered enormously by a redwing chorus. In early spring, at almost any time of day, you may be fortunate enough to hear a babble of bird calls, not unlike the sound a flock of starlings makes before bedding down for the night or, perhaps more fancifully, a rushing stream in full spate. Not starlings, though, but redwings, and it isn’t what is sometimes described as sub-song, when a bird sings a simplified version of its song quietly to itself. The clear six or seven descending notes of the redwing’s true song are nothing like the unmusical chatter of this chorus. Given the timing, it seems reasonable to assume that the behaviour is somehow linked to the birds’ forthcoming migration to a breeding season in Scandinavia. But what do these gatherings achieve? It is hard not to conclude that the birds are passing on information of some sort, possibly relating to their fitness to migrate, which in turn might help them “agree” when to make a move. Back in 1962, Vero Copner Wynne-Edwards (I was about to say that we don’t get names like that anymore, and then I remembered we have a prime minister called Alexander Boris de Pfeffel Johnson), professor of zoology at Aberdeen university, published his theory on group selection in a weighty tome, Animal dispersion in relation to social behaviour. In it he gave hundreds of examples to advance his belief that natural selection could operate at the group level, rather than just on the individual, and the redwing chorus is a case he might have used, maintaining that the choral gathering is an opportunity for the birds to estimate their numbers and adjust their breeding accordingly. Little evidence has been produced for the reality of group selection, a phenomenon that Richard Dawkins aimed to demolish in his 1976 best-seller, The Selfish Gene. It is, however, hard to square selfishness with apparent altruistic behaviour seen in animals and humans, and the time may be ripe for Wynne-Edwards’s theory to be revived in amended form. But to return to the redwings: it is often remarkably difficult to make out the birds at the tops of the oaks, especially as they may be spread out over many trees, but small groups can sometimes be seen moving around. At some invisible signal the chorus would suddenly fade away, but after a few seconds’ silence rapidly build back to full strength. Another prompt that I have been unable to view causes a small group of perhaps 20-50 birds to leave abruptly. The chorus continues unabated, but then a minute or two later another breakaway party departs. I can’t be sure how long any of these choruses lasted, but certainly over half an hour in some cases, and on one occasion I counted a total of at least 190 birds leaving in the space of five minutes or so, after which the wood fell silent.
Just as I embarked on my spring survey work, the weather turned against me – windy, cold and damp – which all helped to suppress bird song and nesting activity. However, I have managed to register more lesser spotted woodpeckers than usual, including two pairs that were interacting with each other one morning, but disappointingly I have still only heard one chiffchaff , which arrived on the earliest ever date of 1st March.
Michael Walter