A walk through Thetford Forest gives the impression that you are in a huge monoculture; the ranks of immense, silver-grey trunked conifers stretch away into their dark, unwelcoming distance. Yet there is some sort of diversity here. Where the stands of conifers run alongside a road there is a thin veneer of deciduous trees, oak and beech, planted perhaps to give passers-by the impression that the woodland is natural. Within the acres of plantation woodland itself, there are stands of different age, collectively providing a varied micro-habitat for birds, animals and plants. While the younger-aged stands support important species, like nightjar and woodlark, mature stands provide nesting sites for crows, long-eared owl and goshawk. There is even some degree of diversity to the types of conifers that have been planted and this can also have an effect on which bird and animal species are present.
Two of the most significant pines in the forest are the Scot’s pine, which has not been a native in England for some 4,000 years, and the Corsican pine, a species that is commonly planted on dry, sandy soils across southern England. The Scot’s pine is a familiar part of the Breckland landscape, its twisted forms often present in the exposed hedgerows and shelterbelts. Many of these were planted during the enclosures of the 19th Century, as they were thought to be a better choice on such light soils than the more traditional hazel or hawthorn.
If you were to map the distribution of crow and bird of prey nests within the forest, you would most likely see a preference for nesting in Scot’s pine over Corsican. This is because of the different shape of the two trees, that of the Scot’s pine being better suited for supporting the nests of crows. Crows prefer to nest slightly down from the top of the tree, generally on a strong limb or in a stout fork against the trunk. Since a new nest is built each year, the old nests become available for those birds of prey, like hobby, that tend not to make their own nest. Over the next few years we will see a change in the types of conifers being planted within the forest. This follows an outbreak of red band needle blight disease. In Britain, the disease is caused by a fungus called Dothistroma septosporum, which has hit Corsican pines across a wide area. A moratorium on the planting of Corsican pine will be in place for at least the next five years, while research into the disease is carried out. Consequently, we are likely to see more Scot’s pine, larch and sitka spruce being planted, which should benefit future generations of crows.