Common tern: the sea swallow

Do we often associate summer migrants to Britain as being hirundines (swallows, martins, etc) and warblers; generally small insect eaters? This is not the case as the tern family clearly illustrate. Terns fly south for the winter returning to us in spring to nest when our warmer seas are (hopefully) teaming with small fish.
The most numerous of the tern family nesting in Dorset is
the common tern (Sterna hirundo). They nest around Brownsea Island, especially on the lagoon, and also at Lodmoor and a few at Abbotsbury. I was surprised to learn that the main loss of eggs and young on Brownsea is due to trampling by foraging sika deer, usually at night when the visitors have gone home and all is quiet.
It is quite easy to distinguish the common tern from the sandwich tern that also nests on Brownsea because it is smaller, it has a red bill and lacks the sandwich tern's scruffy hair cut. It is much harder however, to tell the common tern from the Arctic tern as the Arctic tern has no black tip to its bill, otherwise they are virtually identical. During the months of migration we get both species passing through and so quite often the exact identity is unknown and they are then informally called comic tern's, honestly, no joke! 
The common tern is also informally known as the sea swallow, not just because it migrates like the swallow but because of its pronounced forked tail and swift flight. They can be seen along the shores of Studland Beach and Swanage as well as in Poole Harbour diving in to the sea after sand eels which are their staple diet. Sand eels are actually small silver coloured fish and not really eels.
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