Winter
Adrian Thomas suggests the best ways to encourage hole-nesting birds in your garden
In the vast ancient wildwoods of the past, any old, dead and dying trees would have been peppered with holes: knot holes, rot holes and old woodpecker holes.
Several of our bird species evolved to take advantage of these opportunities. They learnt to seek out cavities whose entrances were just big enough to squeeze into but which opened into roomy inner chambers. Here they could make their nests, hidden from view, safe from the elements and out of reach of anything that might want to snack on their eggs or nestlings.
Most of our gardens are in places where these forests would once have stood, but few of them now contain trees of the right age or size to offer these kinds of natural nest sites.
However, what we do have is the ability to mimic what is missing. Bring on the humble nestbox!
The history of the artificial nestbox is long, if you count the dovecotes that have been around since Egyptian times and became widespread across Europe and beyond. Here, domesticated but free-flying pigeons were encouraged to breed and were then used for meat, eggs, feathers and guano.
However, we can trace the history of nestboxes to help wild birds back to two key figures. The first was the eccentric Charles Waterton who, in the first half of the 19th century, created a nature reserve at his home, Walton Hall near Wakefield, where he hollowed out logs for nesting birds as well as building a tower for roosting starlings.
But it was aGerman landowner, Baron Hans von Berlepsch, who really brought the idea of putting up nestboxes to a wider audience. Around the turn of the 20th century, the Baron set about studying birds’ nesting habits because he wanted to boost the populations of insect-eating birds to help with agriculture and forestry.
He measured hundreds of woodpecker holes, which he considered to be what hole-nesting birds wanted, and then built nestboxes that replicated their size and shape. His designs were so successful that they were mass produced in Germany, with many shipped to the UK for sale.
Box designs have developed considerably since that day, now being simpler and cheaper to produce. It was realised that the exact dimensions of a woodpecker hole weren’t absolutely necessary and that birds would take happily to rectangular boxes, although the right hole sizes remained vital for them.
Some hole-nesting birds use crevices in cliffs; house martins evolved to build mud-globule nesting cups under the overhangs of rocky precipices.
