How to

23 June 2016

How They Keep Warm – Arctic Tern

The arctic tern has the distinction of being the only animal included in this recurring feature that you can see in the wild in the UK. They winter in the Antarctic, but during May and June they fly north to nest, and many of them end up here, mostly around Scotland, Ireland and North Wales. They’re one of the only animals which can be found in both poles, but only during the summer. The almost perpetual sunlight during the polar summers results in a huge surge in plant reproduction, especially plankton, which attracts the huge shoals of fish which the terns prey on.

Despite only being around during the summer, the terns still have to deal with extremely low temperatures, which they primarily do by eating. A lot. Arctic terns have a stupidly high metabolic rate, and will gorge themselves on fish and krill throughout their stay in both poles to supplement the energy reserves they need not only to stay warm, but fly somewhere in the region of 90,000km every year. That’s twice around the world.

Migration is, of course, its own form of keeping warm, as being in constant transit means that the birds always have the best weather for nesting, hunting and fledging. Much like penguins, the terns have reduced nerve and muscular presence in their feet, since they actually nest on the ice. They also nest with other birds, as a protective measure and also a means of being able to find the best building materials.

Their feathers form a very tight seal against the wind, adding to the streamlined design of their bodies. Their wings are pointed, their tail feathers are dart shaped and their bones are hollow. Thanks to these adaptations, they can stay on the wing for hours on end in any weather, and they can even sleep on the wing, which is incomprehensively ridiculous.

On the ground they aren’t quite so coordinated, but when they dive bomb into the water to feed, they’re lethal. The density of their feathers not only insulates them, but has a waterproofing effect so that they don’t get weighed down after diving into the water after prey. 

Callum Davies

Callum is a film school graduate who is now making a name for himself as a journalist and content writer. His vices include flat whites and 90s hip-hop.