Outlook is bleak for the comeback kid

THE area of North County Dublin where I live used to be farmed.

In recent years, however, fertile coastal land has been disappearing under concrete. The last of the local farmers have sold out and, while the lands await ‘development’, large fields are lying fallow.

In the brief interregnum, grasses and wild flowers have free rein; the hawthorn and elder bushes in the hedgerows are blossoming, the skylarks and meadow pipits are back in force, reed buntings are nesting and hares, not seen in a decade, are staging a cautious comeback. Now, whitethroats have arrived and a pair are nesting.

This visitor from Africa, a bird little known to the general public, was here a few decades ago until human encroachment and the cutting back of hedges by over-enthusiastic farmers drove it away.

The little songster gets its name from the white bib which extends down its neck and throat, conspicuous against the light grey of the rest of its plumage. The song is a brisk little jingle, like that of the dunnock, but jerkier and quite distinctive. Whitethroats like scrubby places and will nest in hedges adjoining overgrown fields. Although it’s not that fearful of people and will sing from the top of a bush despite the presence of humans, this is a bird which keeps its distance. You won’t find one visiting your bird table or nesting close to your home.

The comeback kid is famous for spectacular population crashes followed by a plodding recovery from each new disaster. None of the whitetroat’s warbler relatives exhibit such patterns. Chiffchaff willow warbler and sedge warbler numbers fluctuate a little from year to year but the whitethroat is a true drama queen.

The problem first came to light in 1969 when bird ringers in Britain noticed they were catching very few whitethroats. Individual ringers put this down to local factors and the random nature of bird catches but, when the ringing totals for all of Britain and Ireland were calculated, the population was found to have crashed by a staggering 77%.

Of the five million whitethroats which had left these islands the previous autumn, only about 600,000 had returned. There was a further drop in 1974, when numbers reached an all-time low. Several Wall Street-type crashes have occurred since then. The population, like share prices, recovered somewhat in the late 1970s, only to collapse again in 1984. There was another Black Friday-style plunge in 1991; boom and bust seem to be par for the course with this little bird, at least in recent decades. But what causes such dramatic swings?

Ringing, which had helped to document the crashes, also explained why they occur. According to the British Trust for Ornithology, 7,528 whitethroats were ringed in Britain and Ireland in 2005, a fairly normal year, and a total of 345,740 had been ringed up to then. The number of ringed birds ‘recovered’ was 1,070. According to the BTO’s Migration Atlas, which appeared in 2002, only 20 British or Irish ringed whitethroats have been found elsewhere. This is not a huge sample but it’s big enough to give us an outline of the birds’ migration routes.

The young birds of the year start moving south ahead of the adults, their parents staying put while they moult their worn-out feathers and grow new ones; it’s important for migrant birds to have their wings and tails in peak condition when they travel. It’s thought that both adult and young whitethroats converge on the south of England from where they cross the English Channel into France. They don’t seem to linger in France but move on immediately to Spain and Portugal. There they rest and refuel in traditional haunts such as the Coto Doñana. Whitethroats captured by ringers in Portugal put on almost half a gram of fat each day, extra fuel which the birds take on before embarking on the most arduous stage of their journey.

Most of the whitethroats from our part of Europe probably cross the Mediterranean at its narrowest point around Gibraltar. Where they go next is a matter of speculation; only five British or Irish ringed whitethroats have been reported from Africa. The whitethroats’ ultimate destination, however, is known; their winter stomping ground is the Sahel region, just south of the Sahara. This vast semi-desert area has patches of dry grassland, with clumps of hardy bushes and thorny scrub. For most of the year, the Sahel bakes under a merciless scorching sun but the Autumn rains drench the area, creating an explosion of plant growth. The succulents absorb water to tide them over the dry periods of the year. The insects and spiders, which emerge with the rains, are food for visiting birds.

That, at any rate, was how the system used to work. Then a new phenomenon appeared; global warming. Higher temperatures have affected the annual wind cycles in North Africa and these, in turn, have prevented the rains from coming. Longer periods of drought are altering the ecology of the Sahel region affecting man and beast alike. In some years, the rains fail to arrive at all. Climate change is a major factor in the appalling wars which have broken out in the region in recent years. Meanwhile, Nero fiddles and Rome burns; we affluent westerners do nothing to curb our extravagant emissions of greenhouse gases. The outlook is bleak for North Africans and whitethroats alike.

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