Wednesday, August 09, 2006

Sooty Shearwaters Have Longest Migration

According to new research, sooty shearwaters make the longest known migration. The birds travel close to 40,000 miles each year from their breeding grounds around New Zealand to their wintering grounds in the North Pacific. That way, the birds can take advantage of the summer in both the northern and southern hemispheres. Scientists were able to track this route using electronic tracking tags.
Between January and March 2005, 33 birds at two breeding colonies in New Zealand were fitted with tags weighing 6g, allowing researchers to track their journey.

In the autumn of that year, 20 of the tags were recovered when the birds returned to their burrows at the breeding grounds; 19 of the devices had successfully recorded the bird's movements.

Data showed that some birds travelled up to 910km (565 miles) in a day, and dived to depths of 68m in their search for food.
One interesting result of the study is that individual birds do not travel around the circumference of the Pacific, as previously thought. Instead they travel quickly to one of the winter feeding grounds, located near California, Alaska, and Japan, and then return quickly to their breeding grounds at the end of the southern winter. Below is a map showing the travels of the 19 shearwaters with working tags.

Blue = Breeding season activity
Yellow = Flight north
Orange = Wintering activity and flight south

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