Coole is an important location for wintering wetland birds. It is a particularly important site for Whooper Swans. Although once important for Bewick swans, in recent years in line with national trends, the use of the site by Bewicks has fallen off. Large numbers of widgeon, pochard and mallard duck use the site, in addition to smaller numbers of tufted duck, curlew, dunlin and lapwing. The last species and the common sandpiper, is known to breed in the wetlands around Coole and Garryland. There is known to be a strong association between this site and other wetlands in the district. Waterfowl commute between the respective sites, depending on the prevailing water levels. For instance, when winter water levels are low in nearby wetlands, the whooper swans favour Coole.
The woods of the nature reserve support the usual assemblage of woodland birds, each using its own niche. Jay and tree creeper are commonly seen, even in the high visitor use areas of the reserve.