Saturday, August 29, 2009

Hints at the surface

Of course, seabirds hunt on or near the surface and fly above the waves but so much of the ocean’s life lies below the surface. I always consider myself extremely lucky to catch a glimpse of these fascinating animals when they come to the surface, usually briefly. This trip was remarkable in the number of excellent views we had of marine mammals, reptile and fish.

Always one of the most intriguing hints at the surface is the spout of a whale. We were all excited when we saw a large pod of Fin Whales and got to watch their spouts....

Fin Whale is the second largest cetacean (Blue Whale being the largest) and they have a distinctive shape with the small dorsal fin set well back and usually not visible when they first surface, but then appearing behind them a second or two later as in this photo.

and then as they go down the back arches forward and the fin is briefly exposed...

The smaller Minke Whale break the surface in a different manner, coming up snout first and then rolling the back up and forward as the head goes down in a beautiful arching movement.

Their back has a prominant arch when they do this...

The small Pilot Whale is actually a type of dolphin that behaves like a whale. When they breach the surface you can see their dolphin-like shape...

The head however has a large "melon" whose adjustable shape is used in echolocation

When it protrudes from the surface you can see how larger the melon can be...

Common Dolphins are fast and smooth and a real treat to watch. They like to ride the bow waves of boats and so come close. The first image shows an adult and calf - note the two-toned pattern.

This dorsal fin and tail reveal a Hammerhewad Shark just below the surface

I was amazed how close this incredible animal came (with binoculars you could see the shape of the head well)

A fish out of water? This flying fish leaps above the surface. Their specially modified fins permit them to glide considerable distances above the surface, which helps in avoiding predators below the surface.

A rare sea creature, the Leatherback Seaturtle is easily identified by the ridge on their back. Leatherback Seaturtle are the largest reptile in the world and unique among turtles in their leathery carapace, as opposed to hard scales. Unfortunately, they are ciritcally endangered.

This one is munching on a jellyfish (note the tentacle trailing from the corner of the mouth)

Not seen on the pelagic trip but on the coast was another rare marine reptile - the beautiful Diamondback Terrapin, with their distincitve bluish skin.

That completes this series from the Atlantic Ocean...

Saturday, August 22, 2009

Shear water

“Shearwater” is a beautiful word - describing the way these birds speed low across the sea surface as if cutting (shearing) the water with their long and slender (knife-like) wings. To me it also is like a play on the word "sheer" (versus “shear”) because these birds can be seen out in the sheer immensity of the ocean, earning a living in what seems like the harshest of environments to a land bound primate.

The flight style of shearwaters and other seabirds – tilting their body to slice the ocean breeze and serpenting across the surface, rising above the waves while seldom flapping – is a product of their incredibly long and narrow wings. When comparing wing shapes, ornithologists talk about “aspect ratio”, i.e. the ratio between a wing’s length and its depth. For example, large hawks and eagles that soar on thermal currents have broad rounded wings that maximize the wing area and hence increase their ability to ride on thermals. Shearwaters live on the windy ocean and out there their long narrow wings reduce drag, in part because the wing tip is so small in comparison to the length of the leading edge of the wing. It is the aerodynamic properties of this wing shape that make it so common for pelagic species and this is what has made the large albatrosses have the longest wingspans of any living bird (but remember their wings are narrow not broad like a condor for example). Shearwaters can also reduce drag by sticking close to the water surface, especially in calmer winds. In windier conditions, they can also use the updrafts created by waves for lift. In the first two photos of this post, an Audubon’s Shearwater demonstrates their flight style…

And here the larger Cory’s Shearwater also demonstrates, tilting back and forth and gliding low across the water on a calm day…

Of course, even these amazing flyers need a rest from time to time and they are quite happy to sit on the surface. Here are two Cory’s Shearwaters.

Here is a comparison of Cory’s Shearwater (right) and Greater Shearwater (left). You would think that, given their name, the "Greater" Shearwater should be larger but that is clearly not the case.

And here is a mixed flock of Cory’s Shearwaters and Greater Shearwaters. You may wonder why so many birds would congregate in one place. The shortest answer is because thy go where there is good feeding.

To understand why some areas are so rich in seabirds whereas in other areas you can go for miles without seeing even one, you need to understand the food web in the ocean. For seabirds, as with landbirds, everything comes back to primary productivity. Sunlight can only penetrate a certain depth and oxygen can be quickly depleted unless there are currents to stir things up. This is why ocean currents are so vital – they cycle nutrients towards the surface and allow the food web to regenerate itself without exhausting the available resources. Where the water is still, such as in many tropical areas (unless there is a current moving in from colder areas), seabirds are few and far between due to limited feeding opportunities near the surface. The vast majority of the world’s true pelagic species occur in the vast, cold southern oceans and, to a lesser extent, in the cold northern waters (there is more land and less water in the Northern than the Southern Hemisphere).

The above photo of a large flock of shearwaters was taken on the edge of a very large underwater canyon called Baltimore Canyon. In this case, it is the topography of the canyon that forces cold water upward towards the surface and the nutrients that these where upwellings bring create many feeding options for many forms of wildlife… and wildlife that east other wildlife and… you get the picture! That is why we made the long journey (4 hours of straight sailing) to get out to this area.

Of course, it is one thing to use your long wings to slice the wind when aloft but getting airborne in the first place is a greater challenge. An albatross’s or shearwater’s wings are so narrow that they don’t generate much lift in flapping flight. On nesting cliffs, it is easy to dive off the cliff to build up speed and then swoop upward; however, on level land or level water, large seabirds have to run or “paddle” to generate lift. Their long, wobbly, running take off can be rather comical at times. Allow this Greater Shearwater to demonstrate how it is done…

You'll find some more photos of seabirds on my homepage ( My next post with showcase some marine wildlife other than birds.

Thursday, August 20, 2009

The abundant ocean

After participating in the American Ornithologists’ Union (AOU) conference in Philadelphia, I got the chance to do a little birding on the Delaware coast and to take a pelagic trip ( out of Lewes, Delaware. I owe a great debt of gratitude to the local birders who made this possible by taking me out and giving me rides – it is one of the things I love about birding, feeling a part of an international community.

As we left Lewes and got out beyond the breakwater a magnificent sunrise over a calm sea bode well for the day ahead. Indeed, we would be treated to some phenomenal ocean wildlife watching!

We were escorted out to sea by Laughing Gulls such as this youngster following the boat…

One of the first pelagic (i.e. open ocean) species we saw was the Wilson’s Storm-Petrel. The storm-petrels are very small seabirds, completely dwarfed by the large shearwaters and albatrosses. The Wilson’s Storm-Petrel, for example, measures 18cm from head to tail, about the size of a Barn Swallow! With their somewhat eratic flight style I think they look like tiny bats on the ocean. It always amazes me that such tiny birds can make a living out in the ocean squall!

Looking at the above photo, you should notice a few interesting features. The first is the way the feet project beyond the tail. This is because the legs are very long and is an important ID feature when separating this species from several other very similar looking Storm-Petrels. If you’re wondering why the legs are so long, well… my attempt at an answer is below….

Another thing you may notice is what looks like a bump on the bill. This is actually the specialized nostril tubes that extrude salt. They are a feature of the order Procellariiformes, which includes albatrosses, shearwaters, petrels, diving-petrels and storm-petrels. This features earns this group the nickname “tube noses”. Since they are a little hard to see on such a small bird as a Wilson’s Storm-Petrel, I made this comparison with the much larger Corey’s Shearwater to show the tubes to full effect. Notice also how the legs tuck up under the tail with the feet pointing skyward in the Wilson’s Storm-Petrel.

The Wilson’s Storm-Petrel is very common in these waters. In fact, some ornithologists have suggested that this species is among the most abundant of any bird on the planet. It just goes to show that if you can adapt to harsh conditions, there are resources to be found. Indeed, the ocean provides for an abundance of life… hence the title of this post. What amazes me most about seeing Wilson’s Storm-Petrels off the Delaware coast is that they don’t breed anywhere near North America but rather way down in Antarctica and the Subantarctic islands. The thing is that when not breeding during the short austral summer (December – February) they roam the oceans and spend their time feeding at sea far from their breeding colonies. The birds in this photo are just a tiny fraction of a huge feeding flock.

The next two photos show dorsal views of Wilson’s Storm-Petrels and the prominent white rump and pale wing coverts, creating a diagonal bar on the wings (although this can be obscured by harsh direct sunlight)

Revisiting the feeding flock, you can easily see the foraging behaviour known as "paterring" in the following photos. Pattering is hitting the surface of the water with the feet while thrusting the head forward to feed on tiny organisms near the surface, using the wings to balance. The long legs of the Wilson's Strom-Petrel allow them to execute this type of foraging with characteristic "dancing" style.

A closer examination reveals that the webs between the toes are yellow in colour (look at the bird on the left). When I compare Wilson's with other storm-petrels it seems possible that the yellow webs might be a foraging aid, possibly attracting some prey items or assisting them to hunt in low light (many Storm-Petrels also feed at night). On the other hand, older birds develop black spots on the webbing so it could be an indication of age. Interestingly, other long-legged storm-petrels such as White-faced Storm-Petrel also have yellow webbing whereas some of the shorter legged ones such as Leach's Storm-Petrel that typically use more of a hovering style to feed and rarely "patter" do not.

The long-legged Wilson's are so good at pattering that they sometimes seem to be standing or walking on the water...

But when they hop using both legs, their legs trail backwards as the upper body is propelled forward so it looks like they’re on pogo-sticks.

Here are a few more sea dance moves

More to come from the water soon...

Sunday, August 9, 2009

Thistle bath

American Goldfinch are partial to thistle seed and are not too fussy about whether or not they are native or introduced thistles. In order to feed on thistles, they sometimes get right down into their scratchy heads as though bathing in their food supply… Just watch this male go at it from every angle, creating a mist of floating thistle seed!

Of course, it is not just thistles that they like to feed on in this manner!

Monday, August 3, 2009

Ruby red

Hummingbirds are extremely fascinating birds. Perhaps their most famous attribute is their unique flight style with powered wing beast in both the forward and backward direction at remarkable rates of speed, creating the "humming" noise that gives them their English name... In the two shots below my attempts to stop the motion of the wings with shutter speeds below 1/1000th of a second still result in a blur!

But another interesting feature of hummingbirds is the way they derive the colour of their plumage. If you look at the male Ruby-throated Hummingbird below the throat looks black.

But as the head turns the black seems to change to red...

And as is turns more, more red appears

From the right angle the throat ("gorget") is the bright ruby colour that gives this species their name. The reason you can only see the red at certain angles is because the colour is not produced by pigment, but rather by special modification of the barbules of the feathers. Special modifications enlarge certain surfaces to create interference of light waves within each barbule. Some have described the surface of the barbule as like a "tiled floor" or a matrix of keratin and melanin. This interference means that certain wave lengths (colour) are reflected (keratin and melanin have different reflective indices); however, the reflection is also governed by the angle of light.

The result is, of course, splendid!

So I guess the answer to the question when is "black not black?" is "when it is red"!
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