From moorland to forest - how do birds respond?

A mosaic of upland habitats (photo by John Calladine)

Most of the characteristic open upland habitats of Scotland result from millennia of anthropogenic influence. The complex geology, topography and other environmental conditions working with and against man have led to the open often peat-dominated landscapes being described emotively as one of Europe’s last remaining ‘wildernesses’ or as a degraded ‘wet desert’.

Regardless of how the uplands are perceived, the way in which they have been managed has determined their bird communities. Moorlands (in their broadest definition) can support a unique assemblage of breeding waders, gamebirds, passerines and raptors. At the same time, many ecologists look enviously towards Scandinavia and the extensive forests and alpine scrub there and speculate about what we might now be missing in Scotland.

Conifer plantations in the Lecht (photo by Chris Pendlebury)

Following very long-term deforestation, significant and systematic efforts to increase the woodland cover of Scotland started in the 20th Century and continue into the 21st. Initially driven by policies to reduce dependency on overseas sourced timber products, these have progressively evolved to include environmental and ecosystem service attributes together driving a reforestation programme. Current targets aim to increase woodland cover in Scotland from 17% to 25% of its land area. Although that figure is inclusive of commercially managed plantations, there are now many examples of native woodland expansion and recreation across the uplands. Examples include the Scottish Forestry Alliance, the Carrifran Wildwood Initiative, the Mountain Woodlands Project plus many estate-based plantings that are managed by NGOs (e.g. NTS and the John Muir Trust), Forestry Commission Scotland or privately.

Reforestation in response to agricultural abandonment has transformed landscapes in several mountain regions of mainland Europe with associated losses of open country species but increases in forest species. This raises many interesting questions for the future of the Scottish uplands. Since the 1990s the BTO has been involved with a number of ongoing studies that assess how bird communities develop in response to increases in tree cover in the uplands and will give some insights into the assemblages that could potentially develop if large scale changes occur. Our studies include the periodic monitoring of naturally regenerating scrub woodland in the central and eastern Highlands and of mixed regenerating and newly planted native-type woodlands across upland Scotland. Further studies have included assessments of the bird communities found in shrubs within conifer plantations, both at their restructured edges and within regenerating crops. 

The development of these ‘new’ forests will take many decades but already the shrublands and ungrazed exclosures that have been created are supporting important numbers of some birds such as Cuckoo, Willow Warbler, Grasshopper Warbler, Whinchat, Tree Pipit and Reed Bunting. As well as these species that have declined in many parts of lowland Britain, more typical upland species, for example Black Grouse and Short-eared Owl, are found in such areas.

Monitoring of shrubland and woodland colonists is certainly fascinating but what about the losses of open habitat species? Bird Atlas 2007-11 will be a valuable source of data to identify areas that remain important for those open-country bird assemblages, areas that could prove suitable for shrub and woodland expansion, and areas where conservationists might best concentrate efforts to stem the decline of many of those birds.
There are interesting times ahead for the uplands, not just threats to conservation but also opportunities for habitat restoration and expansion. Whether bird assemblages that more closely resemble those of Scandinavia (Bluethroat and Lapland Bunting as regular breeders for example) could ever develop is questionable given the insularity and smaller scale of our uplands, but changes seem likely.  
We are grateful to the AEB Trust and the J & JR Wilson Trust for funding some of our current studies on shrubland birds.
A selection of published scientific papers by the BTO describing shrubland and developing woodland bird studies include:
  • Calladine, J. & Bray J. 2012. The importance of altitude and aspect for breeding Whinchats Saxicola rubetra in the uplands: limitations of the uplands as a refuge for a declining, formerly widespread species? Bird Study 59: 43-51.
  • Calladine, J., Bielinski, A. & Shaw, G. 2013. Effects on bird abundance and species richness of edge restructuring to include shrubs at the interface between conifer plantations and moorland. Bird Study In press.
  • Fuller, R.J. 2012. Avian responses to transitional habitats in temperate cultural landscapes: woodland edges and young growth. In Birds and Habitat: Relationships in Changing Landscapes (Ed. Fuller, R.J.) Cambridge University Press, Cambridge. Pp 125-149.
  • Fuller, R.J., Gillings, S. & Whitfield, D.P. 1999. Responses of breeding birds to expansion of scrub in the eastern Scottish highlands: preliminary implications for conservation strategies. Vogelwelt 120: 53-62.
  • Fuller, R.J., Atkinson, P.W., Garnett, M.C., Conway, G.J., Bibby, C.J. & Johnstone, I.G. 2006. Breeding bird communities in the upland margins (ffridd) of Wales in the mid-1980s. Bird Study 53: 177-186
  • Gillings, S., Fuller, R.J. & Henderson, C.B. 1998. Avian community composition and patterns of bird distribution within birch-heath mosaics in north-east Scotland. Ornis Fennica 75: 27-37.
  • Gillings, S., Fuller, R.J. & Balmer, D.E. 2000.  Breeding birds in scrub in the Scottish Highlands: Variation in community composition between scrub type and successional stage.  Scottish Forestry 54: 73-85.
  • Helle, P. & Fuller, R.J. 1988. Migrant passerine birds in European forest successions in relation to vegetation height and geographic position. Journal of Animal Ecology 57: 565-579.

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