Common Tern
Do not lump them in with other terns, or dare to call them ‘gulls’! This is one seductive seabird...
This elegant ‘Sea Swallow’ has very much become an expected summer fixture of many an urban watercourse up and down the land. Common Terns, like Little Ringed Plovers, are opportunists, originally taking advantage of the many possibilities for nesting along the shorelines of reservoirs and the accidental gravelly islands created in our gravel pits.
They have also been encouraged to breed on artificial tern rafts in urban reservoirs to great success. I remember the introduction of such rafts at my then local patch, Brent Reservoir. They were quickly colonised by many breeding pairs and soon became an avian speciality of that corner of north-west
London. In other areas they have also taken to breeding on flat rooftops. I have especially seen this in industrial estates in Riga, Latvia. Yes, Common Terns have now become very familiar birds to us.
Common mistakes
It is fascinating to think that when Carl Linnaeus first classified this species as the ‘Swallow Tern’, way back in 1753, he was probably eying up the skin of an Arctic Tern.
It is a familiar problem, so I can’t blame him for making that mistake. Besides, as all birders will know much to their chagrin, Common Terns can be tricky to separate from the very similar looking Arctic Tern, its inveterate traveller of a cousin, especially if not seen well or in juvenile/non-breeding plumage. Birders often lump the two when they are unable to tell them apart. They are often referred as ‘Commic’ Terns or ‘Carctic’ Terns, as I have also heard frustrated birders utter.
There are supposedly four subspecies across the world, and the current thinking is that their closest relative is not the Arctic Tern but in fact the Antarctic Tern – another alarmingly similar looking tern. Of the four subspecies the longipennis race, breeding in Central Siberia into China and wintering in Australasia, is quite distinctive during the breeding season with a completely black bill and darker red-brown legs.
However, when it sports its non-breeding plumage you are on your own, because nominate Common Terns in the same plumage, with which they mix, look devilishly similar. As if it wasn’t difficult enough to differentiate our Common Terns from all the other similar looking terns!
Far and wide
It may come as a surprise that the Common Tern has a circumpolar distribution breeding in the temperate and subarctic regions of Europe, Asia and North America. They breed across a wider range of habitats than any of their relatives, including urban environs. Our birds mostly winter off the coasts of western and southern Africa. You may note that the birds look a little different in other parts of the world. I remember being a little flummoxed by the birds purporting to be Common Terns that I saw in southern Texas one year.
I was struggling to convince myself that they were not Forster’s Terns. One thing is for sure though, the Common Tern population is declining in North America with its distribution as a breeding bird being mainly in the north-east of the continent. Perhaps there are fewer than 80,000 pairs, currently.
They were originally hunted for the millinery trade in the 1880s as their wings were used to adorn the silly hats that women wore at the time.
There was an outcry in the UK around the same time against the slaughter of Great Crested Grebes and egrets for women’s hats, and it was the impetus for the birth of the RSPB. The same thing was occurring in the US against the tern slaughter that led to the formation of the Audubon societies.
Subsequently, with protection, the nearly extirpated Common Tern made a massive comeback.
However, by the middle of the 20th Century, the burgeoning gull populations and toxic chemicals in the water systems triggered the start of their existing demise. Now, they are generally outnumbered in North America by the similar Forster’s Tern. There seems to be a reoccurring theme here that, despite being called Common Terns, they are not necessarily the most common tern whereever they are found.
They are certainly not the most common tern in the UK as that accolade goes to the Arctic Tern, that probably outnumber our more urban tern by 2:1. Many of us are unaware of this fact because most UK Arctic Terns mainly nest far from the nearest rush hour traffic jam, in north-west Scotland. So, for most of us, a tern gracefully making its way along a river pausing to plunge dive after a small fish is not only a delight to watch but is highly likely to be a Common Tern.
This idyllic vision is perhaps only spoilt by their regular screeching calls. I for one do not find their calls a distraction to their beauty. I view it as part of the natural urban soundscape during the lazy days of summer.