Objective: Create safe nesting and roosting sites for birds
Definitions
● Dredged sediment = sediment/debris removed from the bottom of water bodies,
such as harbours, lakes and rivers.
● Dredge islands = artificial islands created with the controlled disposal of dredged
sediment.
● Intertidal = the area between high and low tide.
● Nesting = when birds lay eggs and protect their chicks.
● Roosting = when birds are resting, sleeping or preening, i.e. this is an energy-
saving behaviour.
● Shorebirds = birds of the order Charadriiformes; includes waders, gulls and terns
that use coastal habitats for feeding, roosting and/or nesting.
1. Description
Historically, islands made out of dredged material were created as a by-product of sediment disposal, but have since proven to be valuable refuges for roosting, nesting and foraging shorebirds (Buckley & McCaffrey, 1978; Yozzo et al. , 2004; Scarton et al. , 2013). For example, in the USA, over 2,000 islands have been constructed in the Atlantic and Gulf Coast estuaries and are used extensively by shorebirds (Yozzo et al. , 2004). As islands are located away from the shore, they can provide nesting birds with some protection from disturbance, either from predators or humans (Goodship & Furness, 2022). Depending on the target species, vegetation on created islands may require management (see Cutts et al., 2024). Trees and shrubs that colonise islands can be useful for canopy-nesting birds (Yozzo et al. , 2004) but will be a deterrent to shorebirds, particularly gulls and terns which prefer dry ground and open space for nesting (Conway et al. , 2005; Ausden, 2007). It has been suggested (Golder et al. , 2008) that creating artificial islands can stimulate loss of (semi-)natural sites (a) because artificial islands use sediment that might otherwise be used to recharge natural sites, and (b) because it gives the impression that any loss of natural sites can be easily compensated. We are not aware of any evidence supporting these assumptions.
2. Evidence for effects on biodiversity
Birds : Around the world, islands created from dredged material have been shown to support shorebird species as roosting or breeding sites (Buckley & McCaffrey, 1978; Landin & Soots, 1978; Parnell et al ., 1986; Burton et al ., 1996; Powell & Collier, 2000; Erwin et al ., 2003; Yozzo et al. , 2004; Akers & Allcorn, 2006; Aulert et al. , 2012; Scarton et al. , 2013; Chan et al ., 2019). Shorebirds known to breed on dredge-material islands include Little Ringed plover Charadrius
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