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Caspian Tern (Hydroprogne caspia)

The largest tern in the world, and one of the most aggressive, the Caspian Tern can easily hold its own amongst gulls and other seabirds. More than that, it can displace them. There are consistent records of Caspian Terns evicting Herring Gulls from sites where they wish to nest – and Herring Gulls are not pushovers. The Caspian Terns do it by arriving on a desirable spot en masse, and simply staying put, carrying on with whatever displays they were undertaking the day before, and acting as if nothing had happened.

Watching a Caspian Tern feed is a spectacular sight. In common with most terns it is a plunge-diver, and will enter the water with a highly impressive splash, sometimes immersing itself completely. Not surprisingly it tends to subsist on larger fish than other terns, usually those at least 9 cm long (towards the upper limit for a Sandwich Tern, for example), and up to 25 cm at times. The larger specimens are typically taken to the shore, where they are despatched with a few blows of the Caspian Tern’s outsize bill. Some Caspian Terns eat carrion, and even the live eggs and young of other birds.

In Europe most of the colonies are medium sized (10-200 pairs), and some are known to have been occupied for at least 100 years. One of the regular sights of early in the breeding season is High Flying, in which birds lift up more than 100 m above the ground with slow deliberate wing-beats. The Caspian Tern’s High Flight differs from that of smaller terns in that only one or two birds are ever involved, and they never carry fish.