Arctic tern

749px-Arctic_Tern_2006_06_08

Profile

The arctic tern is a small to medium-sized bird living inside both the Arctic and Antarctic circles. Adults are gray or white in color with red beaks and legs and black “caps” on their heads. Sometimes arctic terns have black tips on their wings. These animals look a lot like common terns. Some of the differences between these two animals are that the arctic tern is smaller, has a shorter bill and a longer tail. Birders sometimes confuse these two terns, and unidentified terns are sometimes called “commic terns,” a mix between common and arctic terns. The arctic tern has so short legs that when standing, it almost looks like the bird is crouching down. During the summer breeding season, adults live in the arctic circle in the areas in red on the map below. During the other part of the year, they live in the part of the map highlighted in blue. While they are in the southern part of their range, arctic terns molt. Sometimes this molt occurs so fast that individuals are unable to fly for a period of time.

Sterna paradisaea distr mig.png

Size

Arctic terns can have a wingspan of as large as thirty inches (85 cm). From their beak to the tip of their tail, these birds are at most fifteen inches (39 cm) long. Despite being this size, arctic terns weigh at most 4.3 ounces (120 g). This is about the weight of a stick of butter.

Diet

Because they live near the ocean, arctic terns feed mainly on fish, but also on crustaceans and insects. Their favorite food is sand eels, which they catch during short dives into the water. Although most hunting flights stay within 1.8 miles (3 km) of the individual’s colony, some hunts have been recorded to take place up to 6.2 miles (10 km) from the breeding colony. Sometimes arctic terns will catch insects in mid air or will even startle other birds into dropping their food.

Status and threats

The arctic tern is ranked as Least Concern on the IUCN Red List. The global population of these animals is estimated to be somewhere in between one million and two million breeding pairs. Among the most populated places are Iceland, Alaska, and Russia with hundreds of thousands of breeding pairs in each of these three places. One of the main threats to arctic terns is animals raiding the nests (which are on the ground). Animals that harm the arctic tern population in this way include hedgehogs, minks, and rats. Sometimes livestock will also trample nests. Humans can harm arctic terns by destroying their habitat with development and by over-fishing.

Migration

Many people know the arctic tern for its long migration. It was previously thought that these animals migrated up to 25,000 miles (about 40,000 km) round trip! About five years ago, however, studies were released that showed these animals migrated in a zig-zag pattern. This revelation upped the arctic tern’s migration to about 41,000 miles (71,000 km) round trip. There is a good reason for the terns to go so far out of their way. By doing so, they fly with the wind making their migration go faster and not take as much work.

Arctic terns live for thirty years or more, and this makes their lifetime migration distance total one and a half million miles (2.4 million km)! This is the distance of going to the moon and back three times! These animals also see more sunlight each year than any other bird. This is because it is almost always summer where they are. When they are in the Arctic circle, it is summer there and the sun shines almost all day. When they migrate south to the antarctic circle, it is summer there too because it is in the opposite hemisphere. In Antarctica, the sun shines almost all day again.

The reason this research was not done sooner was because the technology was not available to do this. Previous tracking devices would be too heavy for the small birds to carry, and it wasn’t until a tracker weighing just 1/20 of an ounce (1.4 g) was developed that scientists were able to put a tracker on these birds.

Mating

At the age of three to four years, both males and females mate for life. Arctic terns preform mating and nesting in the Northern hemisphere. This happens during the months of June and July. Males court females in a display that is known as a “fish fight.” This display is not actually a fight but an aerial dance which ends in the male presenting the female a gift of a fish, the bird equivalent of chocolates.

Eggs and young

Nests are made in hollows in the ground and are often hidden in short plants a good distance from the ocean. Every year each female lays between one and three eggs. Males guard the nest and chase away threats by diving at them. Threats include predators or livestock that could trample the nests. The eggs incubate for up to 24 days, and about another 24 days after hatching, the young are able to fly. The hatchlings come in two colors: brown and grey. Different chicks within the same family may be different colors. After hatching, the young will stay with their parents for one to two months before they become completely independent.

Don’t forget to scroll down and comment your guess about what the next animal is!

800px-Nautilus-JB-01

Sources:

Photo credits:

  • Arctic tern – Public domain
  • Arctic tern range map – Andreas Trepte
  • Mystery animal – Public Domain

One Response

  1. Steve Dwire
    Steve Dwire at |

    I’m glad to know they come in both arctic and common varieties. As they say, one good tern deserves another.

Comments are closed.

%d bloggers like this: