Great Shearwaters Circular Migration

Great Shearwaters (Puffinus gravis)
Originally uploaded by Mike at Sea

This past week I have noticed large amounts of these fabulous flyers all heading in the same direction - North. The Great Shearwater follows a circular pattern during the year on its migration route. It flies north along the east coast of the southern and then northern continent of America and then makes its way across the North Atlantic in August to Ireland and Britain where it can be seen off the south-west coasts.

What's unusual about this migration is that it is one of only a few bird species to migrate from its breeding grounds in the Southern Hemisphere to the Northern Hemisphere whereas most other species do it the opposite way round. Eventually it makes it's way down south again along the eastern side of the Atlantic.

Watching them fly is really impressive. They "shear" from side to side following the contours of the waves and swells, every now and again popping up in the turns, before bringing the lower wing to within a hairs breadth of the water or even slightly dipping the tip.

They feed by plunge diving for fish and squid. An interesting note about this is I have seen Magnificent Frigatebirds chase them until they drop into the water This activity, according to a comment left on my Flickr site by Jorn Ake may be a tactic to chase the GS until it regurgitates its food which the MF (no pun intended) then can take. Perhaps it's fear on behalf of the GS or lightening the load in its belly.

It's great to see bird migrations to get a feel for the scope of nature. If you think about it, the straight line distances, which of course they would not necessarily take and so fly longer distances, are:

Rio de Janeiro to New York: 7757 km (4820 miles)
New York to Cork Ireland: 5003 km (3109 miles)
Cork to Cape Town: 9895 km (6149 miles)
Cape Town to Rio De Janeiro: 6062 km (3767) miles
TOTAL: 28717 km (17845 miles)

As I said, that's a straight line distance between these cities which are near their route, not taking in to account the big bulges of northern South America or the bulge of West Africa. You could probably add on another third of the distance again and maybe round it off at 38000 km or 24000 miles. Not quite enough to get a silver card for Air France but an impressive distance to do in a year, whilst also allowing some time out for breeding on the Tristan da Cunha archipelago.

Now that's some journey!