Let’s hear it for a sweet singing bird
Lest you should think he never could recapture, The first fine careless rapture
THE climate has gone mad. Plants are growing out of season, bumblebees are on the wing, pigeons and blackbirds are said to be nesting. Venture forth early on clear calm mornings and you may hear a fine dawn chorus. The robin is the great winter singer but the dominant early morning vocalist is the song thrush. The bird of Home Thoughts, from Abroad sang ‘now that April’s there’, but song thrushes will perform in any season if spring-like weather arrives. The song is unmistakeable; its short phrases, as Robert Browning noted, are always repeated.
Song thrush numbers have fallen steadily in Britain since the 1970s. The bird suffers in cold weather. It’s thought that the British population may fall by as much as 70% during a severe winter. The situation in Ireland is less clear; no recent population estimates have been published but declines were noted when Arctic conditions gripped the country in 1947 and 1963. There may have been a similar drop last year but so many thrushes are singing in the leafy suburbs that it’s tempting to think the bird has held its own. We will know for sure when the results of the new Bird Atlas survey are published. Ever square in the country was visited by BirdWatch Ireland volunteers in the last four years.
It was believed, until recently, that Irish song thrushes went abroad in the autumn and were replaced by foreign ones coming here for the winter. In 1988, the prestigious Birds of the Western Palaearctic Volume V declared that British and Irish song thrushes move to France and Spain. We now know this isn’t so. Over 534,000 song thrushes had been ringed in Britain and Ireland prior to the publication, in 2002, of the Migration Atlas. Of these, 11,400 were found subsequently. Although some adventurous ones visited France Spain and Portugal, thrushes breeding in Britain, the authors declare, ‘are strikingly sedentary’. Only a quarter of those ringed during the breeding season moved more than 20km. Few song thrushes have been ringed in Ireland but there’s no evidence to suggest our birds are any different from British ones. Foreign thrushes pass through the Saltees and Cape Clear each autumn but not enough ringing has been carried out to say whether the Dutch and Scandinavian ones, which visit Britain, reach us.
The song thrush and the blackbird, rivals for our affections, are often compared. Both are fine singers which frequent parks and gardens. They nest in similar places and eat the slugs which gardeners detest. Up to the 1940’s, song thrushes were more numerous than blackbirds. Then the tables were turned; blackbirds became dominant and have remained so ever since. According to the last Atlas estimate, there were 4.4 million blackbird territories in Britain and 1.8m in Ireland between 1988 and 1991. The figures for song thrush were 990,000 and 390,000.
A mature blackbird can weigh up to 108 grams whereas a song thrush will tip the scales at 85 grams. Being bigger, a blackbird needs to find more food, which is a disadvantage in hard times. On the other hand, size is an asset in cold weather. Big creatures lose heat more slowly than small ones, a reason perhaps why blackbirds are less vulnerable in winter. The song thrush, however, has a trick up its sleeve which the blackbird lacks. Snails have hard shells, difficult for a bird to break open. The song thrush carries snails to a large stone, or a rocky outcrop, known as an ‘anvil’. Holding the shell by the lip, it bashes the hapless snail repeatedly against the stone to smash open the shell. The noise is a give-away; a blackbird hearing the hammering will home-in on the sound and rob the thrush of its meal. When young blackbirds try mugging starlings, however, they get a rude awakening; though smaller than song thrushes, starlings are made of sterner stuff and send the bullies packing.
