Durham Bird Club has developed Castle Lake to attract a wide range of bird species with the addition of breeding islands, scrapes, wet ditches, reed beds and hedgerow systems. It is for its birdlife that Castle Lake is quite rightly renowned. During summer and autumn, it is quite possible to see 60-70 species at the site.
A total of 183 bird species (not including those birds regarded as ‘escapes’, generally wildfowl) have been recorded at Castle Lake, with an exceptional 150 species recorded during in around the site in 2011. During summer and autumn, it is quite possible to see 60-70 species at the site and in its immediate locale and over the relative short lifespan of the site, 30 species of waders have been reported. Considerable and increasing numbers of birds, but especially waterfowl and waders have continued to be recorded over the past 20 years, especially during migration periods and the winter. Indeed, away from the Tees marshes, Castle Lake regularly records the highest counts of non-estuarine wildfowl and waders in the county.
To the south of the village is a large body of water formed mainly from ground water and part of a complex of wetlands surrounding the village on two sides. A series of ponds started developing around twenty years ago, with the largest and most important as regards its bird life, now known locally as ‘Castle Lake’. Although this lake is the most recent of the area’s wetlands to form, it has become, by some measure, the largest and undoubtedly the area’s most important area for birds.
Indeed, it has become a very significant site for birds in the North East, and forms a key link within the system of inland lowland wetland on the limestone escarpment in County Durham that include the larger water bodies of Hurworth Burn, Crookfoot and Hart Reservoirs and also much smaller, but still highly important ponds at Wheatley Hill, Cassop and Quarrington Hill.