Monday, July 2, 2018

Shearwaters: Global Travellers

We are about to enter one of the most exciting periods for birding in the Newfoundland calendar of birding events- Summer sea birding. When I say sea birding I'm not really referring to the millions of Alcids that breed on our coasts, or the 10's of thousands of Gannets or the 650,000 Leache's Storm Petrels- those are a given. I'm talking about Shearwaters, Jaegers, Skuas and hopefully rare Terns and Gulls.

Among my favourite birds are the Shearwaters. We have three species that are seen in our waters in from summer into early fall, Great Shearwater, Sooty Shearwater and Manx Shearwater. Only the Manx Shearwaters are here to breed, though many of the bird we may not be breeders. Most Manx Shearwaters breed on islands in Northern Wales, Scotland and Northern Ireland, but they also breed in Iceland various other places south to the Azores. A small number of Manx Shearwaters breed on islands off the southern coast of Newfoundland as well.
Manx Shearwater in flight, Manx Shearwater Newfoundland
Manx Shearwater (Photo: IBC)
The species most likely to be seen are Great  and Sooty Shearwater. These two species can at times be seen in very large numbers, even from shore in Newfoundland in summer and early fall. There have been many times when rafts of 20,000 Sooties and similar numbers of Greats have been reported. They come to Newfoundland to feed and overwinter, these birds are truly global travellers.

Breeding in the Southern Hemisphere, these birds nest in burrows on remote islands, free from mammalian predators. They visit their burrows only at night much the same way our nesting Leache's Storm Petrels do. They spend the vast majority of their lives at sea, they have no use for land except to breed. Also known as Tubenoses, Shearwaters are among several types of birds that have their nostrils encased in tube shapes structures at the bases of their bills. This is just one of the adaptations  that allow Shearwaters to live their pelagic way of life. They are able to drink sea water and then excrete the salt in drops from their nostrils.
Sooty Shearwater nostrils
Sooty Shearwater-Note the tubes at the base of the bill (photo: View from the Cape blog)
Shearwaters are also built for long distance, energy efficient flight. They are easily recognizable by their quick wing beats on very stiff wings, followed by periods of gliding. At times, they cut through the air, low to the surface with a wing tip tearing through the waters edge- hence the name 'Shearwater'. They can be easily distinguished from Gulls, Jaegers and other types of seabirds based on this flight pattern. In strong winds Shearwaters can go long periods of time without needing to flap at all as they expertly ride the wind currents. Note the characteristic Shearwater flight pattern exhibited by the Manx Shearwater in the following video

The two species of Shearwaters most commonly seen off the coast of Newfoundland are Sooty and Great Shearwater. These species seem to time their arrival with the appearance of bait fish such as Capelin. If you get the timing just right you can occasionally see masses of Shearwaters feeding on Capelin just meters from land, as Capelin roll on beaches to spawn.
Shearwater flock
Scores of Sooty Shearwaters resting offshore between feeding frenzies

Shearwaters feeding
Part of a Sooty Shearwater flock
Shearwater feeding on capelin
Sooty Shearwaters- one feeding on Capelin
Sherwater feeding on capelin
Sooty Shearwater feeding on Capeline
Shewaters, sooty shearwaters
Sooties chasing Capelin
Great Shearwater flight
Great Shearwater- note obvious two toned appearance, dark cap contrasting with pale face and under parts. Dark belly patch is often not visible on distant birds.

With only two species likely, identification is usually not an issue. At a distance, Sooty Shearwaters appear plainly dark above and below, the white under wing panels formed by the contrast of the under wing coverts (against the flight feathers and axillaries) often show as just a brief flash and at times may not be visible at all. At closer rangers the white under wings are clearly visible.If a bird is far enough away that it appears entire dark on the upper side and underside and you aren't confident it's a Sooty, then the bird is probably too far away to be identified anyway!
Sooty Shearwater flight

Note on the above bird, even though it is nearly silhouetted against the sky, the pale under wing panel created by the white under wing coverts is still quite visible.

The other Common Shearwater seen in Newfoundland in summer is Great Shearwater. Being a big larger and longer winged than Sooty and having deeper wing beats, this usually isn't an identification issue. Great Shearwaters are medium brown on the back with a slightly darker cap, flight feathers and tail, with a conspicuous white rump band. The pale rump is visible at  long range, but when not visible the differences in size, flight pattern and the pale underside are usually enough to separate Great from Sooty or Manx Shearwaters. As well at close range Great Shearwater has a brown path on the lower belly. This is often not visible at long range.

Great Shearwater flight

Note the pale under parts and contrasting dark cap on white face
Great Shearwater flight
Note the thin white rump band against a darker brown tail

Great Shearwater resting on water

There is a fourth species of Shearwater that is occasionally visible in Newfoundland water's, Cory's Shearwater. having said that it is generally only seen from a ferry, in the later summer when water temperatures are the warmest. It is a species which tends to prefer water temps a little warmer than those preferred by Sooty, Great or Manx. There are a couple of legitimate sightings from land and while it's worth having in the back of your mind, it's usually not a realistic possibility and it's identification is beyond the scope of this article.

It's June 2nd as I write this and capelin are already being reported in some areas, so the Shearwaters can't be far behind. I can't wait!

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