It provides an early wintering site for almost the entire Nearctic population of pale-bellied brent geese.

In addition to the reserve, the site contains The Kingfisher Kitchen, gift and book shop, The Graffan Gallery, exhibition areas, hides, woodland walks, sensory garden, events and activities, free parking, a picnic area[1] and a reconstruction of a Crannog, an ancient type of dwelling found in Scotland and Ireland from the European Neolithic Period to the early 18th century.

[2] The Visitor Centre features award-winning sustainable design including rain water harvesting, natural reed bed filtration systems for waste water, solar power and provides sweeping vistas of the northern shore of Strangford lough from the Kingfisher kitchen.

[4] In the eighteenth and nineteenth centuries, lime was quarried at the site, and processed in Hoffmann kilns.

[8] In 2021 Castle Espie was used as a filming location for the BBC wildlife series Springwatch and Autumnwatch presented by Gillian Burke and in January 2022 Winterwatch presented by Megan McCubbin[9][10][11] Castle Espie (from Irish Caistéal an Easpaig, meaning 'castle of the bishop')[12] is also a townland of 255 acres in the civil parish of Tullynakill and the historic barony of Castlereagh Lower.