Reasons for declines
in farmland birds |
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Nationally, there are three main reasons for the loss of wildlife
on farmed land:
- Farming has become more specialised.
Historically most farms were a mix of grassland and different arable
crops. However, there has been a broad shift to either specialised
dairy or arable farming. Many animals cannot find all their needs
(food and nest sites) supplied in areas dominated by only a few
types of land use.
- Farming has become much more
intensive, with increased applications of fertiliser
and pesticides. Herbicides and insecticides reduce numbers of wild
plants and insects, thus reducing the food supply for other wildlife,
such as birds and mammals. Highly fertilised land becomes less botanically
diverse, while a faster growing and frequently cut sward (eg, silage)
provides fewer nesting sites for birds.
- Habitats such as chalk grassland, broad-leaved woodland,
flower-rich meadows old, unimproved pastures, heathland and river
and coastal grasslands have been lost
through conversion to other land uses, agricultural intensification or through inappropriate or
lack of management (eg, changes in grazing practice). Many plants
and animals declined as they could not adapt to the loss of their
particular habitat.
Land is, of course, being removed from agriculture for housing and
road building. However, in SW England, as in other parts of the UK,
the major change that affects farmland wildlife is the nature of farming
itself, rather than the area lost to development. Mixed farming has
been replaced by intensive dairying enterprises in many areas, especially
in the west. Low-intensity pastoral farming combined with arable is
now less common. The following changes are responsible for the continuing
declines in many farmland birds:
- Loss of weed seeds
- an essential winter food. The change from spring- to autumn-sown
cereals and the loss of over-winter weedy stubbles, together with
the loss of areas of marginal land and the increased use of herbicides
in arable crops, has removed much of this food for birds such as
buntings, finches and larks.
- Loss of insects
- an important food for chicks and many adult birds. Grasshoppers
form 75% of the diet of some chicks and sawfly larvae are an essential
food for grey partridge chicks. Meadows and pastures are the main
habitat for insects but `improvement' of grassland (and arable)
by using pesticides and nitrogen-based fertilisers has reduced insect
populations and so has been a major cause of declines in species
such as grey partridge.
- Loss of nest sites
- some birds breed in scrub, hedges and trees, others are ground-nesters
requiring tussocky grassland or bare or sparsely vegetated land
such as spring cereals. Removal of nesting habitats, or management
such as drainage or too frequent cutting or high stocking densities,
obviously affects birds, with some being unable to breed or, if
they do nest, many broods are lost. Ground-nesting species like
lapwing cannot find suitable bare ground nesting sites among winter
crops.
- Changes in the management
of wet grassland - many species breed and feed on
damp grassland (eg, snipe). Land drainage and the move from traditional
wetland management of high water tables and low intensity grazing
has made much of this habitat unsuitable for many birds.
Predation
Birds of prey, magpies and other natural predators are often blamed
for declines in farmland birds and other wildlife. However, RSPB research
found changes in agricultural practice to be the main cause of the
loss of farmland birds such as skylark, lapwing and
linnet. The most effective means of reversing declines is through land management changes to provide more
insect and seed food and nest sites (eg, cirl buntings recovered because
farmers improved habitat, not by increasing predator control).
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