Learning the ancient languages of birds and bats

The leading shoots of the spruce trees on the acre stick up like slender masts above the billowing sails so recently hoisted by alders, field maples, birches. As nesting places, the dark spruces scarcely rate among our hillside birds, but as song posts they are highly popular.

As the sun cleared the ridge this morning, it picked out three soloists, spaced out on topmost tufts - spaced out, you could think, even in the contemporary sense, as blackbird, wren and willow warbler were giving their all to their favourite arias, heads thrown back, oblivious. The wren was the nearest of the trio of gilded finials, little throat pulsing in contractions of the syrinx, and I pushed the window farther open to catch the ritual, note-perfect response from its neighbour across the hedge.

"The language of birds," wrote the parson and naturalist Gilbert White in 1788, "is very ancient, and, like other ancient modes of speech, very elliptical: little is said, but much is meant and understood."

Since the first attempt to show birdsong in musical notation, in 1650, its precise sounds and meanings have driven ornithologists to extreme efforts of analysis.

After years of relatively simple phonetic equivalents of key song phrases, the new Collins Bird Guide goes into paroxysms of, so to speak, exact approximation. Thus, the song of the wren: "zitrivi-si svisvi-svi-svi-svi! zivusu zu-zu-zuzu! si zirrrrrr svi-svi-svi! siyu-zerrrrr! sivi!"

And this for the song thrush: "Song loud and proclaiming, sounds cocksure and dogmatic; strongly varied, often squeaky and shrill cascades of notes, pauses few and very brief; characteristic is recurring repetitions 2-4 times of same group of notes, eg. kuklivi kucklivi! tixitixi-tixi, pii-eh! trru-trrutrru tixifix! chuchuchu ko-kukiklix! ko-kukiklix! . . ."

Or, as Browning preferred: "That's the wise thrush; he sings each song twice over/Lest you should think he never could recapture/The first fine careless rapture!"

A man who knew his birdsong, if not in quite such phonetic detail, was the 19thcentury Irish botanist Henry Chichester Hart (described memorably by Robert Lloyd Praeger as "a man of magnificent physique, a daring climber and tireless walker, and though his pace was usually too fast for exhaustive work, he missed little").

Hart was gung-ho for the mountains, but also enjoyed a brisk ramble through the spring oak woods of Wicklow, sorting out the songs of the newly arrived warblers: willow warbler, chiffchaff, blackcap and the rest. "No other method," he insisted, "is so valuable or sure as that of the sense of hearing."

Nonetheless, the plaintive whistle of the wood warbler, a rare visitor of which he was "tolerably certain" teased him to the point of shooting one, just to be sure. (That was what one did before binoculars.)

All the little warblers have strikingly different songs, just because so many of them look so similar they even confuse each other. One I have been waiting for is the sedge warbler, whose ratchety voice rings out across the vegetable plot long before I find him with the glasses: an otherwise nondescript little brown bird singled out by a stripe above the eye.

He is famous for his repertoire, mixing as many as 50 phrases in long streams of song, switching from one to another at random and almost never repeating himself in a run of perhaps two minutes.

Among his jumbled syllables are often quick imitations of other birds - chaffinch, linnet, blue tit, sparrow - rattled off as if proving an extra accomplishment in his lonely-heart ads for a mate.

This kind of analysis has been made possible by tape recordings printed out as "sonagrams" that plot the frequency of sounds against time. One of the densest patterns belongs to the grasshopper warbler, whose metallic, monotonous, sewingmachine chirr from the depths of a willow may get through more than 250,000 double notes in a night.

The voiceprints of most of our garden birds show a much more complex and elaborate calligraphy, even in the day-today calls to do with finding food, keeping contact, sounding alarm and so on. The chaffinch, for example, has 14 basic calls that it can vary to convey about a score of signals.

WE pay so much heed to the territorial and amatory proclamations of the cock birds in May's dawn chorus that we forget the small talk of birds continues, largely sotto voce, for the rest of the year. When it comes to bats, too, our fascination with their ultrasonic sonar ignores the clicks, chirps, squeaks and bell-like sounds of their ordinary social intercourse.

Recording the bats' high-frequency sounds in flight has, however, been changing the picture of Ireland's species. Until 1996, the number stood at seven, but the analysis of flight calls has helped to add another two - the "soprano" pipistrelle (with a voice notched up 10 kilohertz from that of the common one), and Nathusius's pipistrelle, picked up initially at a treeline in Co Derry.

Now the hunt is on for the presence of the barbastelle, a medium-sized bat threatened with extinction in much of Europe and never physically found. It hunts low over water, or at treetop height along the edges of woods, and as a "whispering" bat, producing very quiet echolocation calls through its nostrils, is easily overlooked.

The first report of its calls came in 1997, from two visiting bat experts who recorded it in Portumna, Co Galway. This prompted the UK's Vincent Wildlife Trust to extend to Ireland a project using concrete boxes as artificial roost sites in woodland. Sixty-two of them were put up in Portumna Forest Park and another 100 in two other nature reserves in Co Galway.

Although bats began using them at Portumna within a month of their erection, no barbastelle has yet shown (or sounded) its nose. This will, no doubt, tantalise the delegates to the Third Irish Bat Conference at the town's Shannon Oaks Hotel next weekend. It's an indoor meeting, with no fieldwork, because of footand-mouth disease, but some participants, I suspect, will want to slip off to the edge of the woods at evening, bat detector in one hand and mobile phone in the other.

For conference details, contact Kate McAney on 093-35304 or katemcaney@vwt.org.uk