The term 'white-tailed sea bird' is a description of two species of birds, the ERNE (4 letters) and the Ern (3 letters). The ERNE is a large sea eagle that is found in Europe, Asia, and North America. It has a white tail and a wingspan of up to 2 meters. The Ern is a smaller species of sea bird that is found in the northern hemisphere. It has a white tail and a wingspan of up to 1 meter. Both species are known for their graceful flight and their ability to dive for fish.