Action: Provide artificial nesting sites for wildfowl using artificial/floating islands
- Two studies from North America found that a variety of wildfowl used artificial islands and floating rafts, and had high (70–80%) nesting success.
- A replicated study from across the UK found that wildfowl preferentially nested on well vegetated islands, compared to bare ones.
Some species of wildfowl nest on the ground and so as well as providing nest boxes (see separate intervention), conservationists may be able to increase the survival of wildfowl broods by providing artificial island or floating rafts in water bodies.
Supporting evidence from individual studies
A replicated study on two marshland sites in Pennsylvania, USA, in 1976-8 (Brenner & Mondok 1979), found that 56% of 20-34 artificial nesting rafts were used by wildfowl, with mallards Anas platyrhynchos using up to 50% of nest rafts, blue-winged teal A. discors up to 9% and Canada geese Branta canadensis up to 5%. Hatching success on rafts was 80%. Rafts had a wooden frame and Styrofoam centre, an arching roof of wire mesh with two anchors of different weights allowing the raft to float up and down with changing water levels. The authors estimate the cost at $0.85/duckling (in 1979 dollars).
A replicated study at seven prairieland impoundments in Alberta, Canada (Giroux 1981), found that in 1976-8, 1,349 nests from 13 species of wildfowl were found on 75 artificial islands (75 islands searched in 1976-7 and 53 in 1978). Ducks (12 species) nested at densities of 1.8-29.1 nests/ha, with 43-59% success. Canada geese Branta canadensis nested at densities of 0.2-7.1 nests/ha, with 70% success (144 nests). Islands were most productive when small, far from shore and with high vegetation cover. Islands were created before flooding of the impoundments by raising some areas about to be flooded or isolating peninsulas with ditches and were between 0.13 ha and 6.6 ha in size.
A replicated 1992 study of the use of artificial islands and floating platforms in 17 wetland nature reserves across the UK (Burgess & Hirons 1992) found that 11 species of wildfowl nested with greater frequency on well vegetated islands and platforms than on sparsely vegetated ones. This pattern was strongest at inland northern reserves, where all 11 species used well-vegetated sites, but none used sparsely covered ones. At coastal sites and southern reserves the pattern was weaker, but well-vegetated sites were always used by more species. The species studied were eight species of ducks, Canada geese Branta canadensis, feral greylag geese Anser anser and mute swans Cygnus olor. At four sites, the provision of vegetated islands or rafts resulted in the establishment of new populations of five duck species. The review also examines island and platform use by grebes, divers, ground-nesting seabirds, waders and rails.
- Brenner F.J. & Mondok J.J. (1979) Waterfowl nesting rafts designed for fluctuating water levels. The Journal of Wildlife Management, 43, 979-982
- Giroux J.F.O. (1981) Use of artificial islands by nesting waterfowl in southeastern Alberta. The Journal of Wildlife Management, 45, 669-679
- Burgess N.D. & Hirons G.J.M. (1992) Creation and management of artificial nesting sites for wetland birds. Journal of Environmental Management, 34, 285-295