KEY CONCLUSIONS FROM THE 'BIRDS ON FARMS' SURVEY BY BIRDS AUSTRALIA

• As the number of native birds increases with the increasing tree cover, the number of exotic birds decreases threefold.
  
• Where more than 80% of the farm trees are local native species, the diversity of woodland-dependent birds is 43% greater.
  
• Woodland-dependant birds are 8% more diverse in farm sites where at least two different tree species are present. In such sites, honeyeaters are 9% and fruit-eaters 7% more diverse.
  
• Woodland -dependant birds are 21% less diverse in farm sites where trees are regenerated naturally compared with sites where trees had been planted.
  
• Small foliage-gleaning birds are 26% less diverse in farm sites where exotic trees had been planted instead of native trees. By contrast exotic birds are about five times more diverse in these sites.
  
• Cereal cropping reduces the diversity of woodland-dependant birds, particularly understorey birds and ground-nesters.
  
• Bird diversity, especially of ground-foraging birds, is lower in farm sites in which fertiliser had been applied over the last five years.
  
• The diversity of birds, particularly ground-nesting and understorey birds, is less on farm sites where ploughing had occurred over at least 25% of the area.
  
• Bird diversity is re-established about 15 years after the removal of stock from a heavily grazed site. This increase in diversity continues, reaching a maximum diversity, after about 25 years.
  
• Ground-foraging birds are 16% more diverse in sites with native pasture. Diversity is lowest where fertiliser has been applied.
  
• Understorey birds are most diverse in farm sites that are never grazed (5% increase) and are 9% less diverse in sites that are frequently grazed.
  
• Total bird diversity decreased by 25% in sites where much of the ground cover has been removed, leaving smooth, lawn-like grass.
  
• Bird diversity declines in patches of woodland smaller than 10 hectares.
  
• Woodland-dependent birds are 31% more diverse in farm sites surrounded by other woodland. By contrast, exotic birds are 51% more diverse in isolated farm sites.
  
• Woodland-dependent birds are 12% more diverse in broad strips of native vegetation, compared with narrow strips (less than 50m wide).
  
• Ground-foraging birds are 12% more diverse in these broad strips.
  
• Bird diversity increases by 30% for every 10 large trees present at a farm site (tree older than 80 years).
  
• The diversity of woodland-dependent hollow-nesting birds increased by 20% for every 10 large trees present.
  
• A critical age for planted trees appears to be between five and ten years, after which bird diversity is significantly greater.
  
• The critical tree age for woodland-dependent ground-foragers is about 35 years.
  
• For every ten fallen trees present in a farm site, the diversity of ground-foraging birds increases by 30% and bark-foraging birds by 70%.
  
• Total bird diversity is greater in farm sites with leaf litter, particularly when the litter is present in dense clumps.
  
• In farm sites where understorey shrubs are present, there is a 31% increase in diversity of woodland-dependent birds. Small woodland-dependent foliage-gleaner-birds that help to control the spread of eucalypt dieback-increased by 24%.
  
• Noisy Miners are 78% less likely to occur in sites where understorey shrubs are present.
  
• Ground-nesting birds are almost three times as diverse where understorey is present. A river or creek line results in a 21% increase in the diversity of woodland-dependent bird in a farm site.
  
• Bird diversity increases by 3% with each additional farm dam.
  
• Small birds are 28% more diverse and ground-nesters are 29% more diverse when waterways are present.
  
• With the addition of features such as dense shrubs vegetation, shallow areas for birds to feed, islands or dead trees for bird to roost, or fencing to exclude livestock, there is a 14% increase in waterbird diversity. The presence of two such features results in a 28% increase in waterbird diversity. Three results in a 42% increase in diversity, and so on.
  
• Over the past 20 years, 10 million hectares of native vegetation have been cleared in Australia. This clearing has brought about the loss of an estimated 150 million birds. Over the same 20-year period, Australia has witnessed the rapid growth of the national landcare movement. Today there are more than 4000 landcare groups, all committed to restoring farm sustainability in various ways, including re-establishing and maintaining native ecosystems.
  
• Bird's Australia's 'Birds on Farm Survey started in 1995 to asses whether the environmental work carried out by organizations such as Land Care was drawing birds back into rural areas.