Thursday, February 01, 2007

Chiton Killer

One of the delights of the coastline around my suburb, on the Eastern Shore of the Derwent River, are the Sooty Oystercatchers. Although you're more likely to see them during the Winter months, a few venture up to the Tasman Bridge and beyond, almost anytime of the year. I recently watched and photographed a group of four, feeding among the rocks at low tide. I'm usually too intent on getting close enough to get reasonable images, to notice much else. But as I sat on the beach I realised that they were feeding on chitons. The chiton in question is chiton glaucus, a species apparently introduced from New Zealand, in the early 20th century, and now the commonest chiton found in the intertidal areas of South-East Tasmania. You'll probably recognise the mollusc from the image at right. What particularly fascinated me was their ability to deal so deftly with them. The "sooties" were picking them off the water washed rocks and bringing them up to a drier area. They then found a crevice to place them in, while they chiselled away the flesh, again you can see this in the image at right. All over in no time. I tried to get even closer to one of them, but it took flight, but not without its 'prize', as you can see in the lower shot.

4 comments:

Duncan said...

Good one Alan, beaut birds.

BirdingTas said...

Thanks Duncan. For an all black bird, they actually photograph well in good light. I was fortunate that, for once, the elements were with me. These birds are fairly used to humans walking past, which makes approaching them relatively easy.

Snail said...

I'm with Duncan. That's a fantastic series. I had no idea they could prise chitons off rocks.

That's the good thing about blogs---the things you learn from other people's observations.

BirdingTas said...

Thanks Snail, it's comments like your's and Duncan's that keep me blogging-- a mental struggle at times. I suspect the sooties manage to prise them off the rocks when the chitons are under the water and mobile. Apparently they also take limpets, which are probably even harder to prise off.