The Wildlife of Farmyard Barns and Garden Sheds
Outhouses, such as garden sheds and farmyard barns, offer animals a place to shelter from heat, cold or glaring light and provide nooks and crannies for roosting, nesting and hibernating sites, while the web of invertebrate life they support presents predators with an excellent food supply.
From the point of view of the abundance and variety of their inmates, sheds, barns and other outhouses are rather like our gardens — the older, better-established and often more unkempt they are, the more wildlife they contain.
A garden shed filled with stacks of old cardboard boxes and newspapers is a haven for the primitive wingless insects known as silverfish. They thrive between the damp mouldering layers and, with the capacity to digest cellulose, can subsist on a diet of starchy tissue (including plant bulbs), paper and, supplemented by the debris that collects between cracks in the floor. Since silverfish are active mainly at night, they are not often seen.
The other chief inhabitants of this micro-habitat are the diminutive booklice, which likewise relish the paste in book-bindings, and also graze on the fungus mould that develops between layers of damp paper. If the soft wood cladding of a shed becomes very sodden it is vulnerable to a much more insidious fungus —. The reddish-brown spores germinate in wood with about 20% moisture content. Thus nourished, the fungus can spread to drier areas of the walls and, in time, cause collapse of the whole structure.
Among flying insects, wasps and bees commonly choose outhouses as breeding sites. A typical sign of spring is a queen wasp (either the common or the German species), which has probably overwintered in the building, rasping laboriously with her mouthparts at the dried clapboards and making a fine wood-pulp with her saliva. Each tiny load is carried to the chosen site (perhaps a roof-beam), to be fashioned into a nest, a delicate umbrella of greyish paper, only an inch or so across. It shields a few cells, in each of which the queen wasp lays an egg. The hatching grubs develop, after about five weeks, into a small squad of worker wasps which enlarge the nest.
Much less obtrusive is the mason bee Osmia rufa, whose breeding output is negligible by comparison with that of the wasps. On a warm spring day the female may be seen inspecting the walls of buildings for a suitable nest site. In a heavily pitted surface, such as limestone, she seems endlessly exacting in her quest, entering and reversing out of hole after hole until she finds one that is to her liking. Finally, she may decide on a crack between boards, or even a keyhole. Here she lays a small batch of eggs, leaves enough pollen and nectar for them to reach adulthood, and then abandons them.
Wasps and bees, equipped with stings, are well protected from the various centipede, beetle and spider predators that lurk in the gloomy corners of such buildings. Typical indoor spiders are web-builders, trapping the more defenceless resident prey and those, especially flies, that enter from outside. An old shed or barn is often festooned with the dusty, sheet-like webs of Tegenaria domestica, an agile, long-legged spider whose body grows to alarming proportions in the late summer and autumn when there is a surfeit of flies. On the window frames you often find the finer lacework webs of Ciniflo fenestralis, a spider more dependent on crawling insects for food.
In barns, cowsheds and stables, especially where manure is allowed to accumulate, flying insects are especially abundant. These are prey to swallows hawking in the air, and to house sparrows and pied wagtails scouring the ground litter. Such insect food is particularly beneficial to the birds in the breeding season, when the enormous workload of sustaining a hungry brood puts a premium on a rich food supply close at hand. A sparrow with a midden right on its doorstep is, therefore, at a great advantage over one that has to fly further. Much of the sparrow nestlings’ diet consists of dipteran Ries, supplemented by caterpillars, dry grain and, where available, bread. By preference, therefore, sparrows nest in the barn abutting the food source, often tunnelling under the eaves, into the ivy-covered walls or among the thatch roofing if it is the worse for wear.
Some birds, such as the barn owl, have suffered from the loss of nesting sites as the old stone barns have been replaced with modern metal structures, but others have adapted better to the changing architecture of farm buildings. The swallow of today, for instance, can weld its nest of mud and saliva as readily to an iron girder as its predecessors did to an old oak beam.
Barns also serve many birds well as safe, warm roosting sites. In farmyards the crossbeams of some outhouses are sought at dusk by collared doves which, like the house sparrows, prosper in close association with man. They are familiar on farms right up to the north of Scotland, capitalising on the popularity of cereal crops which assure them a supply of grain.
Grain stores in barns attract not only sparrows but also a wide variety of small mammals, although some of these, too, supplement their diet with insects. A garden shed is often home to the relatively innocuous wood mouse, especially in winter when it offers welcome refuge and warmth. From here nocturnal forays are made into the garden to feed. Another incomer is the harvest mouse, which likewise resorts to the comfort of barns for the winter, sometimes in large numbers. (Up to 30 harvest mouse nests were once found in a single stack of hay bales on one farm in Lincolnshire.) Much less welcome, however, is a colony of brown rats, which devour and soil the stores of grain and fodder.
Among the larger mammals, the fox — if given the opportunity — is a frequent visitor to farmyard barns. In the spring foxes sometimes choose the barn foundations in which to excavate their den. In recent years, with its spread into urban habitats, the fox has also taken to making its earth beneath the floors of garden sheds, where it may find less opposition than it does from the farmer. Feral cats, if unmolested, may also establish their colonies in barns, and a score or more cats may operate from there, radiating out to hunt voles and mice, small birds, and even insects in the surrounding countryside.
In winter farm buildings have special survival value to very small birds, which quickly lose body heat in the long cold nights unless they can find a snug roost. Many wrens improve their lot by roosting cheek by jowl in holes in walls, thatch, and even in swallow nests. The wrens, normally pugnacious as individuals in defence of territorial claims, are united in the common goal of shared body warmth and cluster peaceably in a tight ball.
The insulation of their fellows also accounts, in part, for the communal hibernation of some of our smaller bats, notably the pipistrelle and the whiskered. Hundreds may assemble to hang in theof old barns, often representing the combined population of the surrounding countryside. The spectacular long-eared bat, however, shuns the company of others, hibernating alone in stables and cellars.
Various other animals are likewise attracted to the shelter of outbuildings for winter hibernation. Many insects, such as ladybirds and earwigs, overwinter between slats of wood, under eaves and in similar retreats. Most go unnoticed, but a warm winter’s day may coax an unexpected butterfly into activity. Common hibernators are the tortoiseshell and the peacock. Many are conspicuously faded and tatty and only a few are vigorous enough to breed in spring.
Toads and newts also creep into the lumber of a garden shed to overwinter, mostly entering and leaving unseen. Toads sometimes favour a crevice under the paving in a greenhouse, where the higher temperatures help them to eke out their winter fat stores. Among reptiles, slow-worms often hibernate indoors.