open crops for some species to nest in (Hudson et al. 1994; Wilson et al.
1997). It has also reduced vegetation diversity in grassland.- Increased use of herbicides and insecticides, which has decreased the
availability of weed seeds and arthropod prey for birds, particularly for
chicks of some species (Potts 1986; Campbell et al. 1997; Newton 1998).
Management techniques have focused on reinstating spring sowing and provid-
ing winter stubbles, reducing herbicide use, planting strips of unharvested crops
to provide a winter seed source for birds (wild bird cover) and in particular, pro-
viding strips of unsprayed arable (conservation headlands) and/or grassland
(grass margins) around the edges of fields to provide invertebrate food for chicks.
Restricting such measures to field margins minimizes loss of agricultural pro-
duction, while maximizing benefits to birds that prefer to feed close to adjacent
hedgerows.
The quality of hedgerows adjacent to arable fields also influences their use by
birds. The total number of bird species tends to be highest along tall hedges with
many trees, although this is mainly due to these supporting more species associ-
ated with woodland and woodland edge. Some species though, for example
Whitethroat Sylvia communisand Yellowhammer Emberiza citrinellaprefer
shorter hedges with few trees (Green et al. 1994; Parish et al. 1994).
14.12 Conclusions
Although many of the principles of managing specific habitats for birds and
other wildlife are fairly well understood, there is clearly much to be learnt in
terms of fine-tuning habitat management to different sites. It is only by record-
ing management, monitoring its effects and disseminating this information to
others, that it will be possible to optimize the limited resources available for
conservation.
As we have seen, habitat management for birds encompasses a wide variety of
techniques, ranging from low intensity ones such as light grazing by herbivores
to more intensive ones such as lowering the surface of reedbeds. These more
intensive techniques are expensive and only ever likely to be practical on a small
scale. Within protected areas, the challenge for habitat management in the future
is to minimizethe intensity of management needed to conserve threatened
species by increasing the size of existing fragments of semi-natural habitat and
restoring, as far as practical, better functioning of natural processes within them.
Outside protected areas, the main challenge for habitat management in devel-
oped countries will be to identify further practical measures that can be adopted
362 |Habitat management