The case of the killer hedgehog

Another Life: One reason we stopped keeping ducks was their reckless disregard for security, refusing to return to the duckhouse on summer nights and laying their eggs in hidden nests along the banks of the stream.

Once, roused in the dark by a crescendo of quacking, I took a torch to The Hollow and found a hedgehog in mid- plunder, while the duck flapped helplessly nearby.

The appetite of hedgehogs for birds' eggs, and newborn chicks, along with slugs, beetles and earthworms, may undermine the Tiggywinkle image that earns them nightly saucers of Pedigree Chum in more affluent suburban gardens. But it has long been known to gamekeepers raising pheasants, and it earns them special mention as "heavy predators of some hedge-bottom and ground-nesting species" in a new report on the mammal predation of songbirds.

Commissioned by SongBird Survival, a UK charity, it is the work of Prof Roy Brown of the University of London, a biologist and veteran authority on countryside management. He argues that while songbird decline is freely blamed on the intensification of farming, the impact of "increased levels of predator activity", notably by mammals, has been largely overlooked.

The most serious mammal predators in his review are grey squirrels and feral cats. Where grey squirrel densities are high, the breeding failure of small birds nesting in woodland-edge and hedgerow may be almost total.

Field-nesting birds - skylarks, for example - can also be wiped out locally where feral cats are on the prowl (these are not, Brown hastens to point out, well-fed domestic tabbies but cats left to live off the land).

Hedgehogs appear to match rats in serious predation of half a dozen species each (though not all the same birds - hedgehogs get special blame for raiding blackbird and songthrush nests).

Stoats and mink can devastate skylarks and meadow pipits, while foxes do rather less focused damage across most of the songbird list. Badgers can be beastly to skylark and pipit nests, but mostly scavenge on bird remains.

Such "negative interactions" are measured by specific studies in particular habitats. In a five-year study of 11 hill farms in the English Pennines, for example, where neighbouring gamekeepers had stopped shooting stoats, the animals' "activity levels increased dramatically", wiping out the local skylarks and virtually all the meadow pipits. Thus, one abnormal situation was succeeded by another - and perhaps quite temporary - one. (On my own hillside, innocent of gamekeepers and webbed with field banks and stone walls, stoats, skylarks and pipits appear to have a stable, if sometimes mortal, relationship.)

SongBird Survival rejects "the popular view that predator and prey achieve a balance - that is pure wishful thinking". That puts the group right out of step with the Royal Society for the Protection of Birds, which constantly uses this argument to defend the natural role of birds of prey. Brown himself wants more research into the impact of predation - avian as well as mammal - and into the possible need to manage it in the cause of biodiversity.

Introduced aliens among the predators, such as mink and grey squirrel, seem obvious targets for control. Feral cats are unequivocally a dire force in the wild - as the suburbanisation of Ireland is likely to make shockingly clear - and the rat population seems likely to keep pace. But the need to defend "threatened" species can sometimes shade into playing favourites in nature and pursuing controls shaped by human sentiment. Our lovable native red squirrels, for example, at natural population densities, wreak just as much havoc on the birds' nests of conifer forests as do the greys elsewhere.

In Ireland, there is greater tolerance and even enjoyment of stoats in the countryside, now that few farms keep poultry (a stoat's raid on our ducklings was the final discouragement). As rats increase around new rural suburbs, we might, indeed, be glad of any increase in stoats as a natural control.

The case against hedgehogs in Brown's report is somewhat short on specifics: in one study, a temporary increase in hedgehogs meant more predation of wrens' nests; in another, fewer hedgehogs meant more skylarks. Nowhere is there any suggestion that hedgehogs are generally on the rise.

Indeed, The New Hedgehog Book, just published, suggests a general decline, at least in Britain, where even a good habitat for hedgehogs is likely to support no more than one per hectare. And this would have to be free of badgers, the hedgehog's mortal enemy.

Higher popular regard for hedgehogs, many more (but smaller) gardens, heavier road traffic, loss of open countryside - the variables are many, but none suggests a hedgehog paradise. The new book is an update by Pat Morris, Britain's leading hedgehog expert, of one first published more than 20 years ago, a model of entertaining and exact information. In Morris's view, any careful study of hedgehogs shows them as "insignificant predators" on birds.

• The New Hedgehog Book, by Pat Morris, is published by Whittet Books, £12.99