factors other than the physical condition of the habitat can also be important. In
particular, there will be no point in creating suitable conditions for particular
birds if the site is too small, too disturbed, or in the wrong geographical location
to attract them. Other factors influencing bird use at a site might include avail-
ability of food and nest sites, predation, brood parasitism, disease and pollutant,
and pesticide levels. Use of an area by migratory and dispersive birds may also
be influenced by population processes taking place on a much wider scale, and
outside the area being managed (Baillie et al. 2000).
14.4.2Taking account of the requirements of non-bird species
Although various high-profile examples of habitat management have been
enacted specifically to benefit individual bird species, these are the exception and
have usually been undertaken as “crisis management” for severely threatened
birds, such as Kirtland’s Warbler Dendroica kirtlandii, Corncrake Crex crex,
Bittern Botaurus stellaris or Red-cockaded Woodpecker Picoides borealis
(Byelichet al. 1985; Kulhavy et al. 1995; Green and Gibbons 2000; Smith et al.
2000). In practice, most habitat management for birds is intended to maintain
a characteristic habitat and its associated fauna and flora, taking particular
account of the requirements of rare and charismatic species. Conflicts between
requirements of birds and other species are rare, not least because most habitat
management involves maintaining groups of species that have already coexisted
under a previous management regime (see Section 14.2).
Habitat management for plants usually focuses on maintaining or increasing
plant species-richness and maintaining populations of rare or otherwise highly
valued plants. Both can be irrelevant to the suitability of the habitat for birds and
other animals. For plants a major constraint in restoring species-rich terrestrial
and aquatic systems is provided by the high levels of phosphorus derived from
previous fertilizer application or sewage treatment works. Some types of habitat
for birds can often be created at sites with high nutrient levels, although such
conditions can hinder successful restoration of aquatic habitat by preventing
growth of macrophytes. High nutrient levels can also prevent successful restora-
tion of short, nutrient-poor grassland or heathland until time has allowed these
nutrients to leach out.
Birds are larger than invertebrates and occur at lower densities, so usually
require larger areas of suitable habitat. Most insects have annual life-cycles, dur-
ing which they can require a range of different conditions during their larval,
pupal, and adult stages. They can therefore only persist at a site if it provides all
these conditions every year.
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