 There are eight main pools in the reserve , some of which are maintained to support specific flora or fauna . At the centre of the reserve is East Marsh Pool , the largest of the pools , which contains two islands . Tern Island is composed of gravel and pebbles which attracts certain species to breed here , notably common tern and little ringed plover . There are also a number of artificial rafts on the pool , again to induce common tern to breed ; eight pairs did so in 2008 . Willow Island is much larger and more grassy , providing suitable areas for lapwing , common redshank and green sandpiper . The existence of the islands helps to prevent the nests of species such as these being predated by foxes . There are three hides overlooking the pool . An artificial structure alongside the pool is designed to attract sand martins to breed , as they did when the gravel quarry was operational ; this was successful for the first time in 2009 , with eight <unk> occupied and over 40 young fledged . 
