colonizing reed can be kept open by cutting on a short rotation to remove dead
stems. Open water can be maintained by cutting reed underwater to reduce its
vigor.
14.9.7Scrub
The presence of scrub in swamps and fens increases the total number of breeding
bird species, mainly through addition of generalist scrub species (e.g. Hanowski
et al. 1999). Extensive colonization by scrub reduces the value of the swamp or
fen for scarcer wetland species. Established scrub can be removed by cutting
(usually requiring treatment of stumps with herbicide to prevent regrowth),
burning, or clearing in winter when the ground is sufficiently frozen using a
modified blade on a bulldozer (“shearing”). Burning is most effective in the dry
conditions of late summer or autumn, when the fire can burn deep enough to kill
the roots of scrub.
14.9.8Wet woodlands
Wet woodlands can support distinctive assemblages of birds, but are rarely man-
aged specifically for them. An exception is in oak-dominated forested wetlands
managed for timber in the Mississippi and associated valleys in the USA
(so-called “greentree reservoirs”). Here, water levels are manipulated to mimic
natural winter flooding and make acorns and other food available to Mallard
Anas platyrhynchosand Wood Ducks Aix sponsa(Reinecke et al. 1989).
14.10 Managing intertidal habitats
Intertidal habitats comprise mudflats, sandbanks, saltmarsh, and mangroves.
Saltmarshes can be grazed or burnt to create suitable vegetation structure for
birds and encourage preferred food plants for wildfowl. Autumn or early winter
burning is commonly used in the southern USA to stimulate succulent new
growth of food plants for wildfowl, such as Olney Three-square Bulrush Scirpus
olneyifor wintering Lesser Snow Geese Chen caerulescens caerulescens. Burning
also increases access to their nutritious rhizomes, and increases use by loafing and
feeding seed-eating ducks (Chabreck et al. 1989) and icterids, but decreases use
by Marsh Wrens Cistothorus palustrisand Sedge Wrens C. platensisduring the
season that burning takes place. Use of these areas by passerines returns to pre-burn
levels by the following spring or winter (Van’t Hul et al. 1997; Gabrey et al. 1999,
2001). Grazing can be used to create suitable vegetation for nesting Redshank
Tringa totanuson saltmarshes in the United Kingdom (Norris et al. 1997), and
to encourage open swards of Common Salt-marsh Grass Puccinellia maritima
360 |Habitat management