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.

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.

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.

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.