The estuary in north east Wales has been a nature reserve for centuries. During the winter, more than 100,000 waders and 20,000 water fowl make it their home.
Brent Geese and knot on Hilbre Island
Between the Wirral on the English side and the NE Wales coast it covers more than 30,000 acres. It has extensive areas of mud flats, sand flats and salt marsh which attract a great variety of birds, particularly migratory birds.
It's a fantastic place to watch and film birds, especially rare species. And at Gronant, near the mouth of the estuary, there's one very special and endangered migrant.
Gronant is unique because it supports Wales' only remaining colony of breeding little terns. Little terns are dainty sea birds.
They spend the winter at sea off the West African coast feeding on fish. Each Spring, they migrate to this same beach near Prestatyn to nest and lay their eggs on the shingle. Pretty risky business, with all the potential traffic on the beach.
The colony is wardened all daylight hours (4am - 10pm) by paid staff from Denbighshire Countryside Services and a robust group of volunteers. There is also a close working relationship with the RSPB.
When hatched, the small vulnerable chicks are well camouflaged and incredibly difficult to see. But within three weeks of hatching, they will fly. Until then, they are very vulnerable to predators.