2 November 2009
Is this talk about national bird declines just hot air?
No. As well as all these apparent disappearances of birds, there has been a serious, countrywide, decline in the numbers of many birds, including many well known and loved species such as the song thrush, skylark, lapwing and house sparrow.
This decline has been slow and gradual, rather than sudden. Most of the declining species are farmland birds. On the other hand, most woodland species such as the blue tit, nuthatch and great spotted woodpecker are still doing alright. However, declines may have started in woodland habitat also, with lesser spotted woodpecker and willow tit now red-listed because of their severe declines.
Why are they declining?
Extensive research has shown that these declines are caused primarily by changes in agriculture.
1. Increased efficiency
This has led to:
- grubbing up of hedgerows to create larger fields
- ploughing up closer to the edge of the field to increase the planted area
- drainage to dry out damper areas and remove wet flushes from others, all to increase production
2. Changes in cropping practices
This had led to:
- shift from spring to autumn sown cereals
- as soon as one crop is harvested, next one goes in - the land has no time to rest and lie fallow
3. Specialisation of farms and regions to either arable or livestock production
This has resultied in loss of the habitat diversity that many birds need to survive.
4. Increase in the use of farm chemicals – fertilisers and pesticides
5. Increased efficiency in grain and animal feed storage, and exclusion of wild birds from cattle feeding stations
6. Changes in farm buildings
Replacing old buildings with modern ones excludes nesting birds and bats.
How much have they declined?
Although the actual factors that cause the decline are similar to most species, the exact way they act differs, which is why some species have been declining for 30 years, while in others the decline has only become prominent in the past 10 years.
The following lists percentage declines of some bird species recorded in the Common Bird Census between 1970 and 1999:
- Tree sparrow -95%
- Corn bunting -88%
- Willow tit -78%
- Spotted flycatcher -77%
- Woodcock -74%
- Starling -71%
- Turtle dove -71%
- Song thrush -56%
- Bullfinch -53%
- Skylark -52%
- Cuckoo -33%
Policies affecting our birds
Changes in agricultural practices have had a devastating effect on farmland birds, and this process has been fuelled, particularly in north-west Europe, by European agricultural policies.
The 2003 Common Agricultural Policy reform is a step in the right direction, breaking the link between subsidies and production. We think the new policies will help to make a significant difference for farmland wildlife. Today, we understand more about the causes of these bird declines, and we are working to devise new management techniques to reverse the downward trend and benefit farmland birds.
Many people don’t think that this would be the reason for the decline of birds in suburban and urban areas. However, as 80% of this country is farmland, what happens there will affect birds in all habitats. This is especially true of urban populations, since in most cases, the urban and suburban populations are an overspill from the better habitats in the countryside.
The house sparrow is an exception to this. Its populations in city centres are self-sustaining, and the exact way that the exceptionally great declines in centres of large cities are caused may differ in some respects from the surrounding countryside. As yet, the definitive cause for the city centre declines has not been determined.