Tracking of Arctic tern migrations 2007-2008

Greenland Institute of Natural Resources

The study of long-distance migration provides insights into the habits and performance of organisms at the limit of their physical abilities. The Arctic tern Sterna paradisaea is the epitome of such behavior; despite its small size (<125 g), banding recoveries and at-sea surveys suggest that its annual migration from boreal and high Arctic breeding grounds to the Southern Ocean may be the longest seasonal movement of any animal. Our tracking of 11 Arctic terns fitted with miniature (1.4 g) geolocators revealed that these birds do indeed travel huge distances (more than 80,000 km annually for some individuals). As well as confirming the location of the main wintering region, we also identified a previously unknown oceanic stopover area in the North Atlantic used by birds from at least two breeding populations (from Greenland and Iceland). Although birds from the same colony took one of two alternative southbound migration routes following the African or South American coast, all returned on a broadly similar, sigmoidal trajectory, crossing from east to west in the Atlantic in the region of the equatorial Intertropical Convergence Zone. Arctic terns clearly target regions of high marine productivity both as stopover and wintering areas, and exploit prevailing global wind systems to reduce flight costs on long-distance commutes.

The Arctic tern is known to make the longest annual migration in the animal kingdom. During its breeding season, it is found far to the north where summer days are long, and it winters far south in the southern hemisphere, where the days are longest during November to February. This means that the Arctic tern probably experiences more sun light during a calendar year than any other creature on Earth. The long-distance travel of the Arctic tern is well-known both amongst researchers and in the broader public. Now, for the first time, technological advances allow us to follow the Arctic tern on its immense journey, practically from pole to pole.

Four erroneous points were removed from the original dataset: ARTE_410, 9/17/2007 noon; ARTE_370, 9/13/2007 noon; ARTE_373, 9/15/2007 noon and 9/16/2007 noon.
Sand Island (74.263 degrees N, 20.160 degrees W), northeast Greenland, is the breeding colony for these Arctic terns and was placed on the map (red-orange square). Sand Island can be used as the beginning and end of all tracks, but since exact dates of the starting and ending of the migration were not available (high-Arctic zone = continuous day light during summer = poor positions when using geolocators), the tracklines for each animal were not mapped to and from the breeding colony.

Overview

This section explains attributes included in the original dataset. OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only. Should you need other attributes described here, you are encouraged to contact the data provider.

Attributes described below represent those in the original dataset provided by the provider.
Only minimum required attributes are visible and downloadable online. Other attributes may be obtained upon provider's permission.

Attributes in dataset

Attribute (table column)	Description
oid	Unique ID number (generated by SEAMAP)
series	Animal ID
sortorder
id
trjtype
obs_date	Observed date
obs_time	Observed time
trjdays
trjtrans1
trjtrans2
trjstatlat
trjcomplat
trjlon
trjdist
trjheading
trjvel
trjconf
longitude	Longitude of observation
latitude	Latitude of observation
tracktime
equinoxd
code
polar
pointid
month
sp_obs	Species observed
sp_tsn	Species ITIS TSN
obs_count	Observed count