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Artificial islands |
Design and locationShapeThe shape of an island must be always determined by practical considerations. However, teardrop-shaped islands with the narrower and lower portion towards viewing hides, and the wider and higher end pointing away from the hides would provide optimal viewing conditions for the public. At sites where erosion from a particular direction is a problem, the shape and alignment of the islands may have to be determined by the prevailing current. Making the island margins crenulated provides sheltered bays for young birds, increases the length of edge for feeding birds, and allows direct access to the water for island-nesting birds. The surfaceOnce the island has been created, two or three overlapping layers of polythene bags must be laid flat on the spoil base to produce a constant and smooth appearance. Their purpose is to prevent coarse, deep-rooted plants from taking hold. Take care not to leave depressions that will fill with water, sand or any other materials that could damage the plastic. The bags can then be covered with either:
or
For both of these options the polythene is held down with large rocks, pre-cast concrete or mud boulders. You can also use branches of old willow or any other species well adapted to water, sticking them all around the borders as stakes. This option will give the island a more natural appearance. However, perforating the polythene with these stacks can affect its durability if the island is placed in a highly erosive environment. Note for waterfowl islandsThe exact profile of islands for breeding ducks, geese, swans and other waterfowl is not as critical as for terns and waders. It is more important that the islands are allowed to vegetate until they support a tall (0.5-1.9 m) vegetation cover, because this provides ideal waterfowl nesting habitat and reduces predation of their nests (in areas where nests are easily accessible). LocationThe distribution of islands in water bodies will influence their use by breeding birds. For example, islands further from the shoreline support a higher density than those close to mainland. Island distribution will also determine the visibility of birds on islands to the public, which needs to be considered at visitor-oriented reserves or leisure areas. Provision of islands with different amounts of vegetation cover attract different breeding birds. |
Hummingbird hawkmoth - Steve Round
Tree sparrow perched on branch in woodland - Sue Tranter (rspb-images.com, Ref: 1018091)