The latest Breeding Bird Survey for the British Trust for Ornithology in partnership with The Royal Society for the Protection of Birds and the Joint Nature Conservation Committee, has highlighted a significant decline in woodland bird species. The annual survey has revealed numbers down by more than 50% in several species, the worst hit being the willow tit down by 77%.
The reason for the decline is not obvious. It isn’t due to loss of habitat – there is more woodland in the UK today than there has ever been, and, on the whole, modern woodland management is more sympathetic to environmental concerns. The Farm Woodland Scheme and Farm Woodland Premium Scheme have also encouraged the planting of small woodlands.
It may be that the composition and structure of the UK’s woodlands has changed over time. Traditional methods of management such as coppicing provide a perfect habitat for warblers and nightingales, for instance. The coppicing process whereby the wood is regularly cut back creates open woodland with plenty of undergrowth for nesting. Where coppice is left to grow unchecked, eventually the canopy closes and the undergrowth is shaded out. Mature woodland with a closed canopy supports tree-dwelling birds such as the woodpecker, but offers a less diverse selection of species overall.
Many woodland species infact like the woodland edges and open areas where there is shrubby, low-level cover. An explosion in the number of deer in the UK has had a noticeable impact on just this sort of habitat through grazing at the herb and low shrub level. It is quite likely that this is making a serious impact on woodland bird numbers.
Migration has also been suggested as a factor. Several British woodland birds, for example the wood warbler, are annual summer visitors who spend the winter in sub-Saharan Africa. It has been suggested that drought in that region may be having an effect.
Interestingly, studies in the Netherlands have suggested that reduction of habitat quality through traffic noise from nearby roads can significantly affect local woodland bird population.
The BTO relies on volunteers to help them compile the annual Breeding Bird Surveys. If you would like to get involved, e-mail [email protected]