Although broadleaved woodland, an important habitat for many birds, is increasing in the UK, songbird populations are still in decline. An interesting new review of previous research, combined with a field study by the Forestry Commission, has provided some possible solutions to this quandary.
Researchers studied a representative sample of broadland lowland woodlands in England and Wales, assessing the effect of woodland management (silvicultural intervention and control of deer browsing) on vegetation structure, and the relationships between vegetation structure and woodland birds.
Different bird species have different habitat and resource requirements, which researchers identified from a review of existing literature. For example, while hawfinches mainly forage in woodland canopy, dunnocks forage on the ground and willow tits are reliant on the shrub layer for their foraging requirements. Wood warblers prefer mature woodland, whereas song thrush require woodland in a younger stage of development.
As well as summarising resource requirements for 17 target bird species, the study classified different woodland stand structures from A to F, which related to their value to birds:
A – dense low shrub layer
B – dense high shrub layer
C – open understory
D – open canopy
E – closed canopy, few strata
F – closed canopy, multiple strata
The most frequently occurring structures found currently in lowland broadleaved woodlands in England and Wales were stand type E, which are of least value to woodland birds.
The crucial finding from this research is that a very high proportion of lowland broadleaved woodland in England and Wales is of fairly uniform structure. This lack of structural heterogeneity means that our woodlands are missing the mosaic of habitats which different bird species rely on.
Simply increasing the UK’s area of broadleaved woodland is not enough to help songbird populations recover: these woodlands need appropriate, targeted management to deliver a mixture of different stand structures at the landscape scale.
This research has identified a novel approach, providing woodland owners and managers with practical management advice to increase the biodiversity value of their woodland. Creating a more diverse structure through targeted woodland management practices is essential to provide suitable habitat and resources, and to enable woodland bird populations to thrive.
Read the full research paper here.