Commerson’s dolphins

Commerson’s dolphins are mainly found in very shallow, coastal waters around Argentina, the Falkland Islands and the Straits of Magellan. Since this is the first time I’ve been this far South myself, I’ve been very much looking forward to seeing them.

I was not disappointed!

Their colour pattern is striking – and the white patches make them really easy to see, even through the greenish coastal waters.  As we wait on the ship making final preparations are made to leave, these wonderful little dolphins are regular visitors.  To readers back in Scotland who are more familiar with the robust bottlenose dolphins we have around the East Coast, these will seem very tiny indeed – they average only about 150cm long.

They tend to live in small groups – we are seeing them most commonly in pairs and threes – and feed on a variety of different small fish species. They’re a generalist predator.

I’m slightly wishing I had a hydrophone on this trip as it would be great to get a recording of them to hear how they sound.

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Photo credits – Simon Pinder

 

The Wandering albatross

Guest post by Simon Pinder

With a three-and-a-half metre wing-span a wandering albatross effortlessly soars ten metres above the waves. Utilising the wind currents, it can then glide 200 metres without expending energy to rise up over the next peak in the swell. Using this method wandering albatrosses soar around the southern oceans, covering huge distances efficiently. A tagged wandering albatross was recorded covering 6000km in 12 days.

Wandering and royal albatrosses, the great albatrosses, have the largest wingspan of any bird in the world. They breed on Sub-Antarctic islands for example South Georgia, nesting on platforms constructed of vegetation and earth. The female lays one huge white egg which is incubated for about 80 days, after the chick hatches it is fed by both parents who undertake marathon feeding trips to provision it. After almost ten months of its lonely vigil on the nest it is ready to take to the air, it will not return to land until it too is ready to breed. By then it will have circumnavigated the globe for up to 15 years.

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Wandering albatross. Photo (C) S. Pinder

The albatrosses use the strong westerly winds of the roaring forties and the furious fifties way down in the southern hemisphere where land is scarce and the winds build in their uninterrupted passage around the world. The females and young males spend their time in the relative calm of the forties, but the older males, those over 40 years old, live in without competition in the fifties where the stronger wings aid their ageing wings.

One of the effects of climate change is a change in the world’s weather patterns; with more chaos in the system, windier places can become windier. This can pose problems for scientists in the field as windier, rougher seas can be difficult to work on. However, the greater force of these increased winds has allowed wandering albatrosses to travel faster and therefore spend more time foraging. As a consequence, they have become fitter and heavier*. Whether in the future this will result in even larger birds or an over-exploitation of resources is currently unknown.

Simon is a freelance ornithologist and marine mammal surveyor, based in Scotland.

* Weimerskirch, H. et al., 2012. Changes in Wind Pattern Alter Albatross Distribution and Life-History Traits. Science. 335. 211.  DOI: 10.1126/science.1210270

Storm petrels

Black-bellied and Wilson’s storm petrel. Guest post by Simon Pinder

Dragging its leg through the water, pattering its feet across the swell, bouncing over the wave tops storm petrels spend almost their entire time at sea within touching distance of the ocean’s surface.

Storm petrels are very small seabirds weighing (30-60g). They feed on tiny animals in the surface plankton dipping in to this biological soup, sometimes shallowly plunging just below the waves.

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Wilson’s petrel hopping along the water surface. Photo (C) S. Pinder

Wilson’s petrels follow ships for hours feasting food stirred up by the vessel’s passage. They shadow whales for the same reason, benefiting from the whale’s movements to bring plankton within their shallow reach. They are often found alongside other seabirds, such as giant petrels and albatrosses, feeding on the remains of predated penguins and fur seals successfully hunted by killer whales and leopard seals.

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Black-bellied storm petrel dragging it’s foot across the surface. Photo (C) S. Pinder

Black-bellied storm petrels search areas with seemingly random twists and turns, frequently dragging their leg across the sea’s surface as they pivot and zigzag, seizing tiny fish and other inhabitants of the plankton.

They return to land under the cover darkness to visit their single chick hidden in burrows on Sub-Antarctic islands, both nesting on South Georgia.

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Could you spot the difference from a moving ship?  Wilson’s storm petrel (top) and black-bellied storm petrel (bottom). Photo (C) S. Pinder

Simon is a freelance ornithologist and marine mammal surveyor, based in Scotland.