The shallow waters between Holy Island and mainland Anglesey comprise mudflats and sandflats with large areas of seagrass (unusual marine flowering plants) and areas of saltmarsh. These support a wide range of wintering water-birds, especially ringed plover, greenshank, red-breasted merganser and goldeneye. At both the northern and southern end are areas of rare dune heathland and the whole site supports a range in scarce plants such as sea lavender, dwarf rush and golden samphire.
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