The river at Castleconnell is also known for its rich bird life, and particularly its swans, many of which are migratory Icelandic Whooper Swans wintering and breeding on the river.
These reclaimed lands are now regarded as one of Ireland's premier wetlands for wildlife conservation and birdwatching, supporting over 4,000 Whooper Swans and thousands of Greenland white front, Barnacle, Greylagg and Brent geese.
Newtown Cunningham is located close to Blanket Nook, a wetland area that is a wintering site for the rare Whooper Swan.
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173 birds are known from the Reserve including protected species such as Black Stork, Black-billed Capercaillie, Greater Spotted Eagle, the Kamchatkan or Stellar's Sea Eagle, Mandarin Duck, Oriental White Stork, Red-crowned Crane, White-naped Crane, White-tailed Sea Eagle, and Whooper Swan.
It has been identified by BirdLife International as an Important Bird Area (IBA) because it supports populations of various water- and wetland birds including Swan Geese, Greater White-fronted Geese, Whooper Swans, Oriental Storks, White-naped Cranes and Red-crowned Cranes.
It is an important breeding, moulting and resting area for numerous birds including the Kingfisher, Bittern, Whooper Swan, Goosander, Great Crested Grebe, Crane and Sea Eagle.