Management for waterways and wetlands birds may range from intensive hand-rearing of wildfowl, in order to replenish shooting stocks, to setting aside vast reedbeds for a single breeding pair of marsh harriers. The emphasis here is on the creation of suitable nesting sites and, for wildfowl and to a lesser extent waders, provision of feeding and resting areas. It is also important to recognise that management may involve culling, especially on village ponds or small lakes in amenity areas. Feeding of ducks and geese by the public can quickly encourage levels to rise to above that which the pond would naturally support. This results in destruction of pond and bankside vegetation, and eutrophication of the water. Numbers must then be reduced and feeding discouraged to allow the pond to recover.
Breeding and nesting
Below is information on general requirements and some examples of techniques to encourage nesting. Publications of the RSPB and Wildfowl and Wetlands Trust should be consulted for further details.
Artificial nest sites for birds of open ground
Most waders, and other species such as terns, can be encouraged to nest by providing suitable protected areas, such as small low-lying islands of sand or gravel, vegetated or bare according to the preferences of various species. It may be necessary to supply nest or lining materials such as the cockle or oyster shells required by oystercatchers. Some species have more complex requirements for successful raising of young. For example, adult avocets prefer patches of open water with shallow islands, while their chicks require gradually sloping banks in light plant cover for feeding. This may also attract terns and gulls, but both species can be discouraged by winter flooding of the islands. Gulls are frequent unwanted occupants of nest sites designed for other species and it may be necessary to destroy their eggs. In this, as in other matters of detailed site management, the regional office of English Nature should be consulted.
Nest sites for waterfowl
Many species of waterfowl adapt readily to nesting rafts provided with suitable cover or with boxes or baskets. Combining rafts with island sites may increase the breeding density still further. The configuration of the shore and the amount and placement of cover plants are important, since mallard and other waterfowl defend a nesting territory based on sight lines. The ideal shoreline is wavy or castellated, with many individual ‘brood bays’ which can be excavated to the design shown below.
In the breeding areas, food and shelter are vital to the survival of young birds. Both newly hatched dabbling and diving ducks require a high proportion of invertebrate animal food, the nature of which varies with the species, although after a few days dabblers become increasingly vegetarian. The best way to ensure a healthy invertebrate food supply is to ensure a varied aquatic and shoreline vegetation. The breeding area should be about half plant cover and half open water. Plants should have food as well as shelter value.
Ducklings must be able to find shelter at the immediate nest site. The ground should slope very gradually, since even a 50mm (2”) step may defeat day-old ducklings. Rafts should have ramps. Large areas of open water should be broken by clumps of reedswamp or islands with bays which provide areas of calm water no matter what the wind. It may be necessary to provide shoreline wave barriers with suitable openings or ramps.
Nest sites for kingfishers, sand martins and shelduck
Kingfishers and sand martins nest in near-vertical, stone-free sandy banks. They dig their nest holes at least 1.2m (4’) above ground level and up to 1m (3’) deep to escape predators. Sand martins live in colonies, and require extensive areas of bare sand, which are created by fresh vertical cutting from lateral erosion of a stream, rather than by slumping. After several years their nest holes become enlarged to the point where sparrows and eventually starlings can take them over. As this occurs and vegetation gradually encroaches on the face, the colony diminishes unless the cutting is renewed.
Existing or potential kingfisher and sand martin banks can be improved by cutting or building, depending on the problem at hand. Where an existing cliff has slumped or become overgrown, the first step is to clear all scrub and trees from the face. Next, the face should be cut back to vertical, using mattocks. The spoil, in most cases, can be simply pushed to the bottom. Renew a high bank in a series of terraces to avoid having to shift too much material:
Where a potential site is too low, it can be built up provided enough sand is available nearby. Secure corrugated iron shuttering at the top of the existing bank with long stakes driven along the face of the bank. Pack stone-free sand behind the shuttering, tapering the ends of the bank and stabilising the new material with logs held by stakes. (Diagram below).
If possible, build the bank in autumn and leave the shuttering in place until just before the nesting season next spring, to give it a chance to consolidate.
Shelduck dig tunnels in more gradual sandy banks or more often take over old rabbit burrows. Kingfishers, sand martins and shelduck all may take advantage of artificial nest tunnels of a size appropriate to each species. These are especially useful in soil which is too soft to support a simple burrow.
The following general pattern can be made out of timber, driftwood or slabs of rock. The dimensions must be adjusted for the species. Lengths of large or small diameter drain pipe can also be used for tunnels for each of these species. For shelduck, a length of l50mm (6”) drain pipe can be fitted in the top of a clean 22 litre (5 gallon) can. Note that shelduck nests should be set so they slope downwards from the bank.
Nest box for dippers and grey wagtails
The following small open-fronted nest box is suitable for dippers and grey wagtails.
Feeding
Waders find most of their food in mud or silt which is moist or just covered by water. Bare sandy shores and steep banks are not attractive to them. Banks can be cut down as shown to provide wide shallows.
Excavation or hydrological management can be used to create ‘scrapes’ of shallow water and mud. Where possible, two or more hydrologically separate scrapes should be provided, so that one can remain flooded, while water in the other is gradually drawn down to provide areas of very shallow water and wet mud for feeding. The draw down should coincide with the migration periods. For details see Merritt, A (Wildfowl and Wetlands Trust, 1994) and Burgess, Neil D and Hirons, Graham JM (1990).
Waterfowl can be classified into two groups: dabblers, which take mainly vegetable food, and divers, which are carnivorous. Food plants are included in the vegetation tables. Choose plants which provide food requirements through all seasons and remember that some plants, such as reedmace (Typha latifolia), whose seeds are not utilised, are still important because they support high numbers of invertebrates needed by young ducklings and nesting females. Dabblers require 400-600mm (1’6”-2’) of water for feeding. Species such as widgeon and geese prefer gradually sloping open banks for access to shoreside grazing areas. Divers need at least 1m (3’) and can use up to about 4.5m (15’) of water for feeding.
A site’s attraction for dabbling duck and geese may be increased by supplementary feeding with mixed grain, pulped potatoes, acorns etc. In many cases it is undesirable to influence natural population distribution in this way, and feeding must always be limited to avoid taming the birds and making them reluctant to fly. The general rule is to set out feed half an hour before ducks fly in each evening and to feed only as much as can be eaten by morning. About 5 kg (12lb) of food each day is sufficient for 70-80 ducks, where the food rests on a hard bottom, or somewhat more on a marshy bottom where some food is lost in the mud. Temporary winter flooding of shoreside grazing areas can be very beneficial because it liberates seeds still clinging to plants and makes them available to ducks and geese.
Flighting, resting and moulting
Dabbling and grazing waterfowl, outside the breeding and moulting season when their movements are necessarily limited, tend to establish regular daily routines in which they fly to one water body or a safe area of open water at dawn to spend the day. Most wildfowl shooting is centred around the feeding areas since the resting areas must remain undisturbed except for three or four shoots a year at most. Ponds, to be attractive, must be near enough to flighting areas to be noticed. Sometimes flyways are cleared leading in towards a pond. These should be based on the observed pattern of wildfowl flighting and should never be developed to the extent that all tree shelter is removed. ‘Flight’ or feeding ponds can be as small as 15 x 6m (50 x 20’), so long as they have the depth of water needed by different species. Resting ponds should be at least 0.8 hectares (2 acres) in extent to provide safety and freedom from disturbance.
Shelter is essential, particularly on large bodies of water where duck are unable either to feed or to rest if they are constantly blown downwind. Islands provide the best shelter on large ponds, especially if arranged to create areas of calm water between them. Ponds should be surrounded by a belt of reedswamp or marsh vegetation for shelter and to provide a trap for seeds blown over the area. Large ponds need a screen of trees 18-28m (20-30 yards) back from the shore.
Waterfowl require ‘loafing spots’ to rest during bad weather and to sun themselves in summer. These are relatively bare areas of island, spit or mud flat which are sheltered and free from disturbance and predation. They can be easily incorporated into islands managed for feeding or nesting by uprooting coarse vegetation or use of herbicide, or by placing polythene sheets under the topsoil to keep plants from rooting. Beginning in June, first drakes and then ducks moult and are flightless for several weeks. During this period they are highly vulnerable to predation and need dense cover for hiding as well as safe areas of open water.
Predation, competition and disturbance
The main predators of ground-nesting birds are, in order of destructiveness, crows, rats and foxes. Weasels are not usually significant but feral mink, where they occur, can cause great damage. Providing birds with islands or raft nest sites foils mammalian predators, while Dutch nest baskets and boxes designed with anti-crow ‘porches’ keep nests hidden from avian attack. Gulls are both predators on the young chicks of shore birds and competitors for nest sites on open sand or gravel. Pike take a heavy toll of ducklings in some waters.
Competition for nesting sites between members of the same species which use the same habitat is largely unavoidable. The territories of colony-nesters vary from as little as the length which a sitting bird can reach to a few metres in diameter, depending on the species. The only way to encourage more nests is to extend the area of suitable terrain. Waterfowl can be ‘tricked’ into nesting closer together by restricting their visibility, as mentioned above. Swans are notably aggressive toward their own kind.
Ideally, disturbance should be prevented by providing at least 90m (100 yards) of buffer zone between water birds and sources of interference. Diving duck prefer to see threats, and so remain calmly in the middle of open water while people are at the shore, but dabblers and waders take flight at the approach of people on foot or their sudden appearance on top of a bank. Severe disturbance at intervals of a few days is worse than continuous ‘background’ disturbance, since many water birds come to accept continuous noise or passage of people or machines even at close range. The danger of disturbance is greatest on open beaches, where people may be completely unaware that they or their dogs have set up nesting shorebirds and may be trampling their nests.
Grazing animals, especially goats and cows, must be fenced from areas of marginal vegetation otherwise they browse and trample it until it provides neither food nor shelter for birds. Cows may crush pasture nests but usually only on an insignificant scale. Many ground nesters depend on grazing animals in varying degrees to create nesting habitat and feeding areas.
