Birds that belong to the cormorant family are very similar to each other, but the cormorant most often seen in urban Japan is the Great Cormorant, which is commonly found around shallow sea areas as well as inland rivers and lakes. They are also often seen flying over Tokyo metropolitan area as they travel between Tokyo Bay and fresh water areas. During the breeding period, they will have white feathers on the neck and the base of the legs.
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In Japan, the cormorant known for its fishing skills is the Japanese Cormorant, not the Great Cormorant. Rarely seen in inland areas, Japanese Cormorants, which are only found in the sea around Japan, usually live near reefs. In China, it is the Great Cormorant that is known for its fishing abilities.
While both juvenile Great Cormorants and Japanese Cormorants have brown feathers, adults have delicate glossy black feathers. If you have an opportunity to view these species up close, pay attention to their eyes and nostrils. You'll notice that the eyes are a beautiful emerald green, but you won't be able see the nostrils, which can usually be found at the base of upper bill. Although some birds, like cranes, have nostrils big enough to see through to the opposite side, the nostrils of birds that catch fish by diving, such as the cormorant, the booby and the pelican, are closed and appear as a line.
In the 1970s, Great Cormorant populations declined dramatically but today you can see them at ponds in parks and around urban rivers. The reason behind the drop in numbers can likely be attributed to such factors as the loss of major feeding grounds due to the reclamation of inner bays and water pollution. To what, then, can we attribute their rebound since that time? Possible reasons include improvements in the quality of rivers, enabling cormorants to catch fish easier, and the releasing of juvenile fish into rivers for inland water fisheries. This rebound, however, has caused another problem. Because they are large and eat large quantities of fish, Great Cormorants have become a nuisance due to the negative impact they impose on inland water fisheries.
In recent years, some regions have established councils aimed at conserving the Great Cormorant. The activities to co-exist with Great Cormorant are also continued.
Because they have no teeth, birds swallow fish whole without chewing. Cormorants are no exception, swallowing entire fish head-first. If a bird were to consume a fish from the tail, it would have trouble swallowing it because the fish's scales and fins would stick in its throat.
When cormorants fly, they stretch their long neck straight forward, making them look like geese. Because a flock of cormorants will fly lined up in formation, it can easily be mistaken for a flock of geese. Such flight formations are not unique to geese, but can also be seen among such big birds as cormorants, cranes and swans.