Lonely lapwings and the secret world of non-breeders

Early to my desk, I found the hillside seriously somnolent: the ewes still pillowed, their lambs close and dozing. The ocean gleamed with zig-zags of calm and the strand was as bare as the whole bank holiday Monday.

But then, at the far ditch, a bird rose sharply into the air. Dark and floppy-winged, it flung itself aloft, climbing and circling house-high above the pasture, abruptly tumbling and plunging, then rising again – and again.

Even without its distant, creaky cries, the flashes of white beneath the wings declared a cock lapwing in territorial display, new and exciting to me as I watched across the hedge. Wheatears and pipits in that rough meadow, yes, but breeding lapwings were new.

Soon, however, in an odd lurch of hops from one fencepost to the next, the bird vanished and did not reappear. His solitary display, bereft of any female lapwing, had left him to wander on.

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Ireland’s lapwing, like the curlew and other ground-nesting waders, seem doomed to a dismal decline. Their breeding range in Ireland has halved and at the Shannon callows, once a stronghold, numbers are down by more than 80 per cent.

BirdWatch Ireland, with Government support, is seeking help from citizen scientists in a national survey of breeding pairs: follow Project Lapwing on Twitter or at Biodiversity Ireland.

Meanwhile, my lonely lapwing set me thinking of all the birds in springtime that never find a mate. “Floaters” as ornithologists call them, have a largely unknown life. But now, from eagles to sparrows, their role in conserving bird populations is under growing study.

‘Limit to multiplication’

Floaters themselves are scarcely new – Darwin was aware of non-breeding birds. And one of Ireland's finest field naturalists, Charles Moffat, was the first to hint at their significance. In a paper in the Irish Naturalist in 1903, on the spring rivalry of birds, Moffat offered "some views on the limit to multiplication". They challenged the widespread idea that, for bird population to remain stable, up to 90 per cent of new young birds must die.

Spring rivalry for territory, he argued, “results in such a parcelling out of land as must limit the number of breeding pairs to a fairly constant figure and prevent indefinite increase. . . at the same time condemning the less powerful individuals to unproductiveness rather than death.”

In what’s sometimes known as “Moffat’s Equilibrium”, non-breeders are available to fill nesting vacancies, a buffer that can protect populations from decline or extinction.

Some floaters may hang around on the fringe of breeding territories, living secretive, unstudied lives or perhaps sneaking the odd “extra-pair copulation” as they wait for a vacant territory.

In birds such as crows, swans and waders, non-breeders occur separately in flocks, sometimes of nearly half the population. Some may also act as "helpers" to active families. In Greenland, with ornithologist David Cabot, I watched as pairs of barnacle geese, marshalling their chicks against marauding Arctic foxes, were joined by non-breeding geese in a fierce, deterrent beating of wings.

With May so much the month of the cuckoo, I inquired of Google Scholar as to the occurrence of male floaters: how many of them go on carolling in vain? But any such research eluded me. Spare females, I learned, do exist and may be hunted out of the territories of breeding cuckoo pairs.

Notorious lifestyle

To describe them as pairs seems ill-fitting, given the notorious lifestyle in which the female lays her eggs in the nests of unwitting songbirds (in Ireland, mainly the meadow pipit).

Indeed, the female is rarely seen, keeping well under cover between her swift and parasitic sorties, but also hunting the hairy caterpillars that most other birds reject. Her sex life can be arduous, given the frequent, pressing attention of the male, which can sometimes yield up to 25 eggs in a season. Females have been seen with two or more pursuers.

Such sexual harassment has even been linked to the colour of their plumage. Most cuckoos of both sexes resemble some sort of hawk, with greyish back, barred underparts, long tail and direct, dashing flight. But some females are quite rufously brown, like their young.

Experiments with decoy females have found that males “attempted to copulate more frequently and excessively with the grey morph”, suggesting evolution of the brownies as a female-only force for selection.

As I write, early in May, no cuckoo has arrived on this side of the hill. The Burren and Connemara usually have the greatest density of pairs, but the species is rapidly declining in both islands.

In the UK, the British Trust for Ornithology tracks the migration of five satellite-tagged cuckoos on their spring return from the forests of the Congo. It has a webpage that maps their routes, and on last inspection four of the birds had arrived in England in April.

In Ireland, records in the whole island are collected by Dr Damien McFerran at the Ulster Museum (habitas.org.uk/records/submit-cuckoo-record). Do be sure it wasn't a collared dove.