Forestry Commission Picture Library /Isobel Cameron
Woodland management for birds: Birds and woodlands in Wales
Establish coppice management with its
associated varied field layer.
Establish appropriate grazing regime.
Managing grazing and browsing
Grazing is traditional in many woodland areas, particularly the Welsh upland oak woods, where livestock are often given access from adjacent farmland. This contributes to the development of closed canopy woodland with a sparse shrub layer and has been a key factor in woodland management, creating the open woodland habitats preferred by many priority bird species. However, livestock can suppress sapling development (often preventing regeneration) and the development of a dense shrub layer. Grazing is a key management tool, but it needs to be managed sensitively to deliver the objectives identified in the planning process.
Browsing by deer, ponies, goats, and rabbits has been occurring since before people began to actively manage woodland. Deer may be increasing in Wales, and in some areas goats have also been increasing; browsing by both can impact on woodland structure.
Understanding the effects of grazing and browsing on the development or suppression of woodland vegetation is essential to ensure that other management will create the structural diversity
intended. Grazing is beneficial in maintaining a characteristic woodland type, eg open upland oak woods suited to wood warblers or pied flycatchers. However, without control, it is easy for grazing and browsing pressure to cause damage to woodland structure and its regenerative capacity; the degree to which grazing or browsing affects the structure of the woodland will depend on the relative proportions, and availability, of palatable to non-palatable vegetation.
Relatively light grazing pressure maintains the ground layer in good condition, and enhances variations in its structure, eg tussocky grasses and dwarf shrubs; this is important for ground-nesting birds, eg willow and wood warblers, because it retains the conditions that shelter their nests.
Higher grazing densities can compromise structural diversity and many bird nesting opportunities and niches for invertebrates are lost. The ground layer is an important source of invertebrate biomass, and heavy grazing will keep the vegetation short, limiting its potential value to biodiversity. Temporarily high stocking rates that exploit spring vegetation growth will also dramatically heighten the risk of nest trampling.
With increases in stocking density, the more palatable species, including seedling trees and saplings, will be prevented from developing, and where grazing levels are intense, only the inedible species will survive. With time, this has implications for the species composition of the wood, and
Plate 3 Where deer densities are high the shrub layer can be absent.
Plate 4 Where grazing pressure is appropriate, glade habitat is maintained without damage to the shrub edge.
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