The Arctic tern (Sterna paradisaea) is a small seabird that is known for its incredibly long migration route. The Arctic tern flies farther than any other bird species, migrating from its Arctic breeding grounds to the Antarctic region each year. This round trip journey covers over 70,000 km (43,000 miles), which means the Arctic tern sees two summers every year. The Arctic tern’s migration route takes it over oceans, along coastlines, and across continents as it travels between its northern and southern homes. Understanding the flight path of the Arctic tern provides insight into the amazing endurance flights these birds undertake.
Breeding Grounds in the Arctic
The Arctic tern breeds in the far north polar regions during the summer months. Their breeding grounds extend along Arctic coasts and islands in Alaska, Canada, Greenland, Svalbard, and Russia. Here they nest in small colonies, laying 1-3 eggs in nests on the ground. After the eggs hatch in around 3 weeks, the chicks fledge in another 3-4 weeks. By late August or early September, the fledglings are ready for the long journey south.
Fall Migration Route
As the days shorten and temperatures drop in the Arctic autumn, the terns begin their southbound migration. They generally follow coastlines along North and South America to reach their Antarctic summering grounds. Some key stops along their southbound route include:
- Atlantic Canada and the Northeastern United States
- Southeastern United States and the Gulf of Mexico
- Caribbean Islands
- Coastal South America
The terns fly during the day and rest at night, traveling an average of 200-300 km each day. Some individuals fly over 9,000 km nonstop from the Arctic to Antarctica! Their journey covers around 25,000 km on average from Arctic to Antarctic regions.
Summering Grounds in the Antarctic
The Arctic terns arrive at their Antarctic summering areas starting in late September/October. They spread out across a wide swath of Antarctic and subantarctic coasts and islands. Key summering grounds include:
- Southern tip of South America
- Falkland Islands
- South Georgia Island
- South Orkney Islands
- South Sandwich Islands
- Antarctic Peninsula
- Ross Sea and Weddell Sea coasts
Here the terns feast on the rich ocean life of the Southern Ocean. They fatten up for the long return trip north.
Spring Migration Route
As the southern summer ends, the Arctic terns begin migrating north again in February and March. They follow a similar coastal path up the west coast of South America and North America. Then they spread out to breeding sites across the Arctic by May.
Some major stopover sites on their northbound trek include:
- Southern coast of South America
- Caribbean Islands
- Southeastern United States
- Northeastern United States and Atlantic Canada
Again the terns fly mainly during the day, resting on coastal waters at night. After flying over 25,000 km south the previous autumn, they now complete a similar epic journey in the opposite direction.
Total Round Trip Distance
By migrating from the Arctic to the Antarctic and back each year, the Arctic tern logs an incredible distance. The total round trip covers more than 70,000 km (43,000 miles). This is the longest regular migration of any bird species on Earth.
Some key facts about the Arctic tern’s huge migration route:
- Total round trip distance: >70,000 km (>43,000 miles)
- One-way trip distance: 25,000 – 30,000 km (15,500-18,600 miles)
- Daily travel distance: 200-300 km (125-185 miles)
- Top speed: 90 km/h (56 mph)
- Total flight time for round trip: 90 – 100 days
This extreme travel allows the Arctic tern to experience endless summer, breeding in the far north before heading south to feast in the productive Antarctic seas. They migrate farthest of any species on the planet!
Route Variations
While the Arctic-Antarctic migration is typical for the species, some populations follow slightly different routes. For example:
- European breeding terns may migrate down the west coast of Africa
- Birds nesting in Siberia follow coasts in East Asia
- Some individuals cross oceans and interior landmasses
Researchers are still studying the many migration strategies and routes taken by different tern groups. Satellite tracking technology is helping reveal their full range.
Navigation and Orientation
Navigating tens of thousands of kilometers over oceans and continents is an incredible challenge. How do Arctic terns manage their marathon migrations? They use a variety of cues:
- Instinct – following innate migration direction and timing
- Sun compass – using the sun’s position for orientation
- Stars – using stars for nighttime navigation
- Earth’s magnetic field – sensing magnetic cues for latitude
- Polarized light – judging direction from light polarization patterns
- Landscape – using landmarks and coastlines
They also likely rely on mental maps, spatial memory, and experience to reach their target destinations after previous journeys. Their navigational systems and adaptability are remarkable.
Threats and Conservation
The Arctic tern’s specialized migration strategy makes it vulnerable to certain threats:
- Climate change – altering breeding and feeding habitat
- Overfishing – reducing food supply
- Pollution – contaminating marine food webs
- Disturbance – disrupting breeding colonies
- Predators – taking eggs and chicks
However, the Arctic tern remains widespread and numerous. Population trends seem stable so far, with an estimated global population of 2-3 million pairs. Ongoing conservation efforts aim to protect important breeding colonies, migration stopover sites, and Antarctic feeding grounds to ensure the survival of these epic migrators.
Unusual Abilities and Adaptations
Some key abilities and adaptations help Arctic terns achieve their extreme migrations:
- Strength and stamina – high aerobic capacity, strength to fly thousands of miles
- Navigational systems – sun, stars, magnetic cues, spatial memory guide migration
- Dynamic flight – superb aerial agility for feeding and migration
- Salt gland – excretes excess salt from marine diet
- Plumage patterns – black cap and grey wings reduce glare
- Long lifespan – 30+ years allows multiple journeys
These adaptations make the Arctic tern a true champion of migration. Their abilities continue to astound biologists and birdwatchers alike.
Research Methods
Scientists have used various techniques to study Arctic terns and track their migrations:
- Banding – metal ID tags allow return records
- Geolocators – light-level loggers record migration routes
- Satellite tags – transmit location data remotely
- Stable isotope analysis – chemical signatures from feathers reveal origins
- Field observations – surveys of breeding and wintering grounds
- Genetic analysis – population genetics reveals connectivity
Advanced tracking technology is yielding new insights into the Arctic tern’s flight paths and migration habits. Combined with field studies, this research helps expand knowledge of the remarkable travels of this species.
Comparison to Other Migrations
The Arctic tern’s 70,000 km round trip migration is unmatched in the animal kingdom. Some other epic migrations include:
- Humpback whale – up to 16,000 km between polar feeding and tropical breeding areas
- Leatherback turtle – 15,000 km between nesting and foraging sites
- Monarch butterfly – up to 5,000 km between Canada and Mexico
- Bar-tailed godwit – 12,000 km between Alaska and New Zealand
While other species conduct lengthy migrations, the Arctic tern’s pole-to-pole journey is incomparable for its great distance covered. They are true champions of flight!
Fascinating Facts
- An Arctic tern chick born this year could migrate with the same individuals for over 20 years due to the tern’s long lifespan.
- Fossil evidence shows the Arctic tern lineage has likely made these marathon migrations for over 125,000 years.
- An Arctic tern flying from pole to pole will travel further in its lifetime than the distance from Earth to the Moon.
- The Arctic tern has the longest daylight period of any animal, experiencing up to 20 hours of sunlight each day during portions of its migration.
- Arctic terns defend their breeding grounds aggressively. They will dive-bomb intruders, earning them the nickname “sea swallow.”
- Ancient seafarers used to capture Arctic terns and release them far from land. They followed the bird’s orientation back towards their breeding colony.
Importance of Migration Route
The Arctic tern’s extensive migration route:
- Allows access to abundant prey in both northern and southern polar oceans
- Provides extended daylight period for feeding and rearing chicks
- Allows avoidance of harsh winter conditions at higher latitudes
- Enables nesting in predator-free Arctic habitats
- May facilitate avoidance of parasites
This specialized migratory strategy is key to the Arctic tern’s survival. It provides a competitive advantage over less mobile species. But it also requires incredible fortitude to endure long periods of non-stop flight across vast distances.
Conclusion
The epic migration of the Arctic tern is one of nature’s great wonders. By traveling from Arctic to Antarctic regions each year, they complete an astonishing >70,000 km round trip journey. Their route traverses oceans, coastlines, and continents as they pursue endless summer in both hemispheres. This extreme migration cycle is made possible by the tern’s high mobility, advanced navigational capabilities, and physiological adaptations for endurance flight. While threats exist from climate change, pollution, and disturbance, the Arctic tern remains a robust and widespread species. Ongoing conservation measures aim to protect the tern’s critical breeding and feeding habitats across its flyway. The Arctic tern’s globetrotting migration will continue to inspire awe and research for generations to come.
