Bird of the Month
Warbler species can look so alike that song is the more reliable guide. Among the genus Sylvia ( silva, a wood), the fresh-leaf green and dead-leaf brown birds, with grey variations in between, are specially challenging – if visible at all, once spring has sprung.
Fortunately, because its numbers are rising, one whose appearance is as distinctive as its song is the blackcap ( Sylvia atricapilla). Were it not for the ‘cap’, they could be one of the grey variations of the Sylviidae, notably the garden warbler; but the cap, neat as any skullcap – black in the male, rust brown in the female – is unmistakable.
They are also easier to see because 3,000-odd winter here. Unlike the garden warbler, the blackcap does not migrate from tropical Africa; but it remains a predominantly summer visitor – from Morocco and southern Europe.
London is a good indicator of its rise in numbers both in summer and winter. In the 1940s, none bred in the centre and few farther out but, by the mid-1990s, across London this had risen to 82 per cent. Wimbledon Common now hosts more than a hundred breeding pairs. Warmer weather has also contributed to the winter migration, predominantly from Germany, with birds choosing to come here rather than Spain and Portugal. It’s the male’s rambling song and vociferousness that causes most excitement among bird lovers. John Clare called it The March Nightingale:
Now sallow catkins once all downy white
Turn like the sunshine into golden light
The rocking clown leans oer the spinney rail In admiration of the sunny sight The while the Blackcap doth his ears assail
With such a rich and such an early song
He stops his own and thinks the nightingale
Hath of her monthly reckoning counted wrong
‘Sweet jug jug jug’ comes loud upon his ear
Those sounds that unto may by right belong
Yet on the awthorn scarce a leaf appears…
The blackcap is also called the ‘northern nightingale’. Gilbert White described its song as ‘a sweet, wild note’; hence the recent book on birdsong, A Sweet, Wild Note by Richard Smyth. The blackcap’s song is Smyth’s favourite: ‘Cracked, drunken, loud, littered with chitters and whistles, and generally all over the shop – it doesn’t sound like music to me, and I think that’s sort of the point. The blackcap doesn’t give a damn what it sounds like to me.’
The females migrate later than the males; so, when they arrive, a male’s song is all important: first as an announcement, then in comparison with other males – the terrain offered and lustiness promised by the strength of its delivery. Blackcaps are undergrowth nesters. It is conservatively estimated that ten per cent in Britain are killed by cats.