• Name: Common Tern | Sterna hirundo
  • Size: 77-98cm wingspan
  • Life span: 12 years  
  • Diet: Common Tern mainly eat fish (i.e. Sand eels), but also consume shrimps and other crustaceans, small squid, marine worms, and leeches.
  • Reproduction: Common terns are monogamous, which means they mate with only one partner during a breeding season; with a female laying 2-3 eggs between April and June.
  • When to see: Spring and Summer (April to September)
  • Where to see: Common terns breed along coasts with shingle beaches and on rocky islands, i.e. Green and Stony Island, Samson | Annet and the Western Rocks in Scilly. 
  • Conservation status: ICUN Redlist | Least Concern (Global).  Birds of Conservation Concern 4 | Amber (UK)
  • Population Trend: Decreasing
  • Threats:  Human activity/disturbance through increases in recreational activities, naturally fluctuating water-levels flooding their nest sites, habitat loss from coastal development, erosion, pollution and invasive vegetation at nesting sites.
  • Fun Fact: A Common tern, when incubating eggs, flies off the nest in order to poo at a distance of 5-50 m (16-160 ft), doing so in water nearby or on the territory of another tern.

Description: Often called "sea swallows" due to their long tails, Common terns visit Scilly in Summer and can infrequently be seen at other times of the year; passing to and from breeding grounds elsewhere. 

They have a sliver-grey-white colouration with a black head and red bill. Their flight is graceful and they are mainly seen hovering over water before diving, arrow-like into the sea for fish. 

They are generally seen in Scilly in small numbers where their distinctive high-pitched chattering call can be heard. 

Sadly, numbers of Common terns in Scilly have dropped by 85% since 2000 and are now at risk from being lost as a breeding species here.  Their decline is marked by an Amber Conservation Status and is due to climate change and overfishing globally.

In 2018 very few Common terns returned to Scilly at all; 10 birds showed an interest in nesting on the south end of Annet in late May but no eggs were found.

Want to know more?  Check out our latest Seabird Monitoring & Research Technical Report for the most up to date information about how this charismatic species is fairing in Scilly.


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With thanks to Joe Pender for the Common tern image