The terns are arriving back, a sure sign of summer! Pretty soon, the Dublin Port colony, among others, will resound to the calls of breeding Common and Arctic Terns. So, the Dublin Bay Birds Project has compiled a photo guide below to aid in telling these two quite similar species apart. We hope you’ll find it useful when out birdwatching in Dublin Bay or further afield!
Arctic Tern in breeding plumage. (Jan Rod).
Common Tern in breeding plumage. (Cameron Moore).
The profile of the bird can be really useful when viewing these species at a distance, when features such as bill colour are less easily seen.
Guide to the Arctic Terns profile. Note the rounded head, relatively short bill and neck which lend to the ‘hunched’ appearance. (Jan Rod).
Guide to the Common Terns profile. Note the longer neck and bill compared to the Arctic Tern. (Cameron Moore).
More often than not, you will be observing terns in flight. Once more the shape of the body is quite useful. From the bill to the beginning of the wings is quite short on the Arctic Tern, while the tail streamers give a lengthened appearance to the end of the bird. The Common Tern looks more equally balanced on each side. The Arctic Terns wings are narrower than the Common Terns and their flight is more buoyant. One of the most useful id ‘tricks’ however is the underside of the wing, which is illustrated below.
Arctic Tern in flight. (Kevin Murphy).
Common Tern in flight. (Brian Burke).
Have a lovely summer and happy seabird watching!
Thanks to Dublin Port Company for supporting and funding this work.