Posted by: Dan | March 21, 2007

Icons of Migration: Arctic Tern

It’s time to pay homage to the champion migrant, the Arctic Tern (Sterna paradisaea). These birds enjoy summer year-round, as they migrate from one pole to the other in accordance with the seasons.

The Arctic Tern is the World Champion for migration. They migrate from Maine and areas further north to the coast of Africa and then south to Antarctica. Some migrate over 20,000 miles a year–The average Arctic Tern in its life will travel a distance equal to going to the moon and back!

Fun facts below the fold…

  • Arctic Terns are medium-sized birds, with a length of 33-39 centimetres (13-15 in) and a wingspan of 76-85 cm (26-30 in). They are mainly grey and white plumaged, with a red beak (as long as the head, straight, with pronounced gonys) and feet, white forehead, a black-nape and crown (streaked white) , and white cheeks. The gray mantle is 305 mm, and the scapulars are fringed brown, some tipped white. The upper wing is gray with a white leading edge, and the collar is completely white, as is the rump. The deeply forked tail is whitish, with grey outer webs. The hindcrown to the ear-coverts is black.
  • Arctic Terns are long-lived birds, with many reaching twenty years of age. They eat mainly fish and small marine invertebrates. The species is abundant, with an estimated one million individuals. While the trend in the number of individuals in the species as a whole is not known, exploitation in the past has reduced this bird’s numbers in the southern reaches of its range.
  • Arctic Terns mate for life, and in most cases, return to the same colony each year. Breeding begins around the third or fourth year. Courtship is elaborate, especially in birds nesting for the first time. Courtship begins with a so-called “high flight”, where a female will chase the male to a high altitude and then slowly descend. This display is followed by “fish flights”, where the male will offer fish to the female. Courtship on the ground involves strutting with a raised tail and lowered wings. After this, both birds will usually fly and circle each other.
  • When molting its wing feathers during the winter, the Arctic Tern rarely flies, instead speading much of its time resting on small blocks of ice at the edge of the pack ice. Its molt happens so quickly that some individuals are nearly flightless for a while.
  • It is one of the most aggressive terns, fiercely defensive of its nest and young. It will attack humans and large predators, usually striking the top or back of the head. Although it is too small to cause serious injury, it is capable of drawing blood. Other birds can benefit from nesting in an area defended by Arctic Terns.
  • When hatched, the chicks are downy. Neither altricial nor precocial, the chicks begin to move around and explore their surroundings within one to three days after hatching. Usually, they do not stray far from the nest. Chicks are brooded by the adults for the first ten days after hatching. Both parents care for hatchlings. Chick diets always include fish, and parents selectively bring larger prey items to chicks than they eat themselves. Males bring more food than females. Feeding by the parents lasts for roughly a month before being weaned off slowly. After fledging, the juveniles learn to feed themselves, including the difficult method of plunge-diving. They will fly south to winter with the help of their parents.

Note: Yes, much of this information was gathered via Wikipedia – my apologies, but it simply is the most useful reference for a non-expert such as myself. Oh well – it’s still a fascinating bird.


Responses

  1. PZ blogs about a “Back to Genesis” conference which will feature astronaut Col . Jeffrey Williams. I checked the link and found that Cornell’s own John Sanford will also be speaking.

  2. Wouldn’t it be cool to be these birds and see the world like this? Great post and love the map!

  3. Wikipedia helps us all sound like experts! It’s amazing that such prodigious travelers mate for life, and even more phenomenal that they find their mates year after year.


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