How songs of springtime reveal four birds in one

A small bird whose song is one of the most distinctive sounds of spring in Britain is actually four separate species, scientists have discovered.

A small bird whose song is one of the most distinctive sounds of spring in Britain is actually four separate species, scientists have discovered.

The chiffchaff, a green warbler that floods into Europe by the millions from its wintering grounds in Africa, is now arriving in Britain. Its repeated chiff-chaff high-note, low-note song is as unmistakable as that of the cuckoo's, if not so well fixed in the popular imagination, and much more widespread.

But sophisticated computer analysis of it - followed up by DNA evidence - has led scientists to realise that Europe and western Asia are annually visited by four distinct species of chiffchaff rather than one.

The bird that normally occurs in Britain, and which is now to be called the common chiffchaff, stretches in its range from France through Scandinavia to Russia.

But the one that visits Spain and Portugal is separate, and is now to be called the Iberian chiffchaff, while the Canary Islands chiffchaff is different again. To complete the picture, the bird that occurs from Turkey down to Afghanistan is also a separate species, now to be called the mountain chiffchaff.

A group of German scientists, led by Andreas Helbig from the University of Greifswald in north-eastern Germany, has established the differences, and reported them in Ibis, the journal of the British Ornithologists' Union. Using sonograms - computer print-outs of the different songs - they show, for example, how the common chiffchaff, Phylloscopus collybita, differs from the Iberian chiffchaff, P. brehmii.

The first has "an ascending note, ranging from about 2kHz to 5kHz, with a harmonic upper tone which is always present", while the second "produces a note starting with an ascent, then descending with a longer downstroke, a quite unique structure not found in any other chiffchaff". Analysis of the DNA of birds of each of the four types has confirmed that they are separate species.

Steve Dudley, administrator of the British Ornithologists' Union, said: "This is quite a feat, because essentially all four of them resemble each other very, very closely.

"There are subtle differences such as bill structure, but in terms of their general appearance they are very, very similar."

One of the newly described species, the Iberian chiffchaff, has now been added to the official list of birds occurring in Britain - now numbering 553 - which the British Ornithologists' Union maintains. A bird seen at Brent reservoir in north London in 1972 was tape-recorded and one of Dr Helbig's German colleagues has confirmed its identity from analysis of the song.

Several other records are awaiting confirmation, including that of the bird on this page, seen, heard and tape-recorded last summer at Portland, Dorset.