Little voice

The hawthorn has a little fan of lettuce-green at every node, but still its silhouette before sunrise is gaunt and wintry. In a dark scribble of twigs above my head, a tiny ball of fluff, a wren, was vehemently engaged in song. I could see the black needle-points of his beak, trembling against the sky's one patch of light.

The strength of wren-song is a cliche among the countryside's surprises: so much power from so small a source. But here was something else to wonder at. Wrens not only sing in territorial rivalry; they have an understanding about it. The bird above me made a song-statement, five seconds long, loud, clear and staccato: "This-isme-standing-here-in-my-ownplace-in-the-best-of-all-possiblewor lds!" One beat of silence, then an identical declaration rang out from the shadows of a willow bush 100 metres distant.

Five such exchanges per minute, for many minutes, and always they heard each other out. I could feel the stillness of the wren above me, the intentness of its listening. And each time, though I was braced for it, the vigour of its response, with stubby tail cocked like a trigger, seemed to shake the thorn-tree to its roots.

But for such operatics, Troglo-dytes troglodytes could seem an almost wilfully obscure little bird, nosing around like a mouse in the lower reaches of hedges or woodland undergrowth. But it has an adaptability that brought its ancestors out from America, across the Bering land-bridge, to found a European race of wrens that extends from Ireland to the Urals, and from Norway to the Mediterranean.

No hedgerow bird has its willingness to creep into holes after spiders or squeeze through the labyrinth of tangled roots and twigs. The dunnock, or hedgesparrow, is adapted to explore the ground for food, turning over little bits of leaf or twig; the robin, to keep watch from a vantage-point and fly down to seize small morsels. Only the wren searches incessantly in three dimensions, even upside-down on a wall. An inveterate insect-eater with a thin, sharp beak it has nothing to gain from human bird-tables, and its occasional exploration of rural interiors has none of the robin's bright-eyed awareness of people: it is looking for insects and more insects. Given this single-mindedness, together with a year-round defence of territory and a structured insistence of song, the uncertainties of the male wren's spring love-life come as some surprise.

The cock builds a number of nests - up to half-a-dozen - in March and April, many of which are never used. Some are started with a hectic bout of construction and then abandoned. Others are painstakingly woven, the bowl roofed over with a dome so that the nest becomes egg-shaped, with a front entrance, a threshold and even an eaves over the door to catch rain-drops.

"I have often said to myself," wrote the Rev Edward A. Armstrong, "Here's a rainy day. I'll go and see where the wrens are building". This Belfast-born clergyman, one of the century's outstanding ornithologists, wrote a fine monograph, The Wren (1955) in which he explained the durability of a finished nest. It is built with wet material which, as it dries, contracts and twists so that the scraps interlock, weaving a tough shell from delicate fronds of moss or grass.

It's the female wren, however, attracted into the territory and inspecting the nests on offer, who decides which one she likes and wants to furnish. Nearly always, it is the one best hidden from predators, and she may help finish it by installing a mattress of feathers. She lays her half-dozen eggs - white, or slightly speckled - in April and, in most summers, goes on to rear a second brood.

The cock, meanwhile, may acquire a second wife, occasionally even a third. These just drift in, as it were, attracted by the neighbourhood as well as the male display. It's an optional and successive polygamy, not the harem-gathering of some game birds, and probably happens mostly in the rich woodland, full of nest-holes, that is the wren's idea of heaven. Where life is leaner - in a rocky niche of some bleak Atlantic island, for example - monogamy is probably quite sufficient (more than 20 wrens' nests were once found on Little Skellig).

The wren's domestic arrangements are certainly no more unconventional than that of its neighbour in the hedge, the dunnock. This archetypal little brown bird, my garden's least conspicuous inhabitant, repeatedly startles me on winter mornings with the sweetness and strength of its song. And in spring the dunnock's love-life can be positively suburban in its taste for irregular liasons.

The female dunnock builds the nest by herself, a mossy cup lined with hair or feathers, and defends an exclusive territory against other females. The males then compete with each other to defend the female territories. Where a male is satisfied with one female territory, the result is monogamy, but the male often expands his territory to include a second female. The wives then chase each other jealously, with the male hopping about in between them.

A female, on the other hand, may stake out a territory too big for one male to defend. When a second male comes on the scene, there's a fight. If neither comes out on top, then both males agree to defend the territory jointly and share the female. It is an uneasy alliance, not helped by the female slipping off through the shrubbery, away from the first male, to solicit copulation from the second as well.

There is always some advantage to these quirks of behaviour. Once the dunnock chicks are born, both fathers collect food for them, working side by side. And those extra nests the wren builds can make cosy, life-saving roosts on winter nights.