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Birds and woodland structure: opportunities from woodfuel

Birds and woodland structure: opportunities from woodfuel. Rob Fuller British Trust for Ornithology. PART 1: OVERVIEW OF EFFECTS OF WOODLAND STRUCTURE ON BIRD POPULATIONS IN LOWLAND WOODS illustrated by coppice cycles effects of structure on key resources .

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Birds and woodland structure: opportunities from woodfuel

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  1. Birds and woodland structure: opportunities from woodfuel Rob Fuller British Trust for Ornithology

  2. PART 1: OVERVIEW OF EFFECTS OF WOODLAND STRUCTURE ON BIRD POPULATIONS IN LOWLAND WOODS • illustrated by coppice cycles • effects of structure on key resources

  3. Elements of structure within woodland of importance to birds permanent open space edge structures / ecotones foliage complexity – field and shrub layers canopy structure – height and cover tree size and maturity

  4. Establishment • whitethroat • dunnock • tree pipit • yellowhammer Effects of coppice rotations on bird populations

  5. Canopy closure (c. 6yrs) • willow warbler • garden warbler • blackcap • bullfinch Effects of coppice rotations on bird populations

  6. Post canopy closure • more hole-nesters • low bird densities • low bird diversity • community stability persists over many decades Effects of coppice rotations on bird populations

  7. 12 100 10 8 80 6 4 2 60 0 4 8 14 20 30 40 20 0 % m Coppice height Coppice cover 4 8 14 20 30 Index Index 40 40 35 35 30 30 Field layer density Shrub layer density 25 25 20 20 15 15 10 10 5 5 0 0 4 8 14 20 30 4 8 14 20 30 Age of coppice (summers of growth) Fuller & Henderson 1992 Bird Study 39:73-88

  8. Bird density and tree height, Bradfield Woods 4.5 Willow Warbler 3.5 2.5 1.5 0.5 0 0 2 4 6 8 10 12 14 3.5 1.6 Nightingale Garden Warbler 1.2 2.5 density (terr/ha) 0.8 1.5 0.4 0.5 0 0 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 height (m)

  9. Insects --- tree species microclimate decaying wood dampness Fruit ---- shading tree species Tree composition Edge structures Gaps FOOD Tree size Growth stage Edge structures Tree holes Foliage complexity SHELTER Patch size Linkages Resource nexus Network structure Patch types SPACE

  10. PART 2: RECENT POPULATION CHANGES IN LOWLAND WOODLAND BIRD POPULATIONS • changes in habitat structure through canopy closure and deer browsing are one mechanism possibly driving some of these changes

  11. Widespread resident passerines Short-distance migrants Long-distance migrants Some specialist residents

  12. Reduction in woodland management • Demise of coppice management • Weak timber markets • Increased canopy closure and shading • Reduced open space and low vegetation • Simplified bird communities

  13. Intensive deer browsing and canopy closure have similar impacts on understorey structures and bird populations

  14. PART 3: WHAT MIGHT WOODFUEL MANAGEMENT MEAN FOR WOODLAND BIRD POPULATIONS? WILL IT INTRODUCE BENEFICIAL STRUCTURES? • coppice structures are highly variable • little is known about how thinning affects habitat quality for wildlife

  15. Deer browsing Densityof standard trees Density of coppice stools Low foliage structure Migrant bird population Rotation length Tree & shrub composition Coppice vigour

  16. Warbler density (terrs. ha –1) Songbird density (terrs. ha –1) 100 40 20 50 84 86 88 90 92 84 86 88 90 92 SHRAWLEY WOOD (lime coppice) Fuller & Green (1998) Forestry 71:199-218 Recent coppice Singled coppice Old coppice

  17. CONCLUSIONS Woodfuel has great potential for enhancing avian diversity and abundance of some declining species There is uncertainty about exactly what management systems will become widespread and what habitat structures these will generate Will deer reduce habitat quality of young growth created by woodfuel managent? Structured monitoring of biodiversity responses is essential to determine what woodfuel actually delivers

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