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Oystercatcher, Eurasian

Identify and index birds in Southern Africa
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Johan van Rensburg
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Oystercatcher, Eurasian

Unread post by Johan van Rensburg » Tue Nov 22, 2016 10:05 am

I wrote about the events leading up to me getting to see a Eurasian Oystercatcher, Haematopus ostralegus, at Saint Lucia recently. This species does not feature on our Forum Index as yet, so I guess some work must be done…

Image

The visiting oystercatcher is a striking black and white wader with a long bright red bill that it at times uses to break into shellfish when the softer fare along the shoreline like crustaceans, worms and insects becomes scarce. The amazing thing is that each individual inherits a particular shellfish feeding technique from its parents. Despite the name, oystercatchers are not known to eat oysters and in fact favour mussels.

I love eating black mussels and collect them off the rocks north of Saint Lucia whenever I get the opportunity. When healthy molluscs are disturbed, they clamp shut. The more you try to pry them apart, the tighter the shells clamp shut. Despite having primate hands and opposable thumbs, you will be thwarted by these stubborn molluscs, unless you use a tool to help. So, how do birds with nothing more than sharp beaks for tools deal with them?

A study done in 1967 in Europe showed that one group of oystercatchers specialises in stabbing the prey in shallow water. To feed, bivalves have to open their shells underwater. The birds deftly plunge their bills between the shells, and sever the adductor muscle that holds them together. Once the mussels are immobilised, shucking them is relatively easy.

Another group of oystercatchers pries shellfish from rocks exposed by the tide, and batters a hole through the tightly closed shells. Within this specialty, some pound only the anal side, and others, the gill side.

Chicks learn one technique of opening hard-shelled molluscs from their parents, and become proficient with years of experience. When they grow older, they teach their own chicks the same method. You are either taught to be a stabber or a hammerer! Either way, both these techniques are fraught with danger. A hammering of too tough a shell can cause a broken bill and a stabber can get trapped if it takes on a powerful bivalve. There is obvious skill required for either method. I’m wondering if our own African black oystercatchers have similar feeding habits that it passes on from one generation to the next, like their Eurasian cousins…

Eurasian oystercatcher sightings are rare in South Africa with probably less than ten visitors per annum.
697 Latest lifers: Sooty falcon, American golden plover, Temminck's stint, Cape long-billed lark, Agulhas long-billed lark, Karoo eremomella

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hilda
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Re: Oystercatcher, Eurasian

Unread post by hilda » Tue Nov 22, 2016 1:53 pm

Johan van Rensburg wrote:This species does not feature on our Forum Index as yet, so I guess some work must be done…


Thank you for adding the Eurasian Oystercatcher on your Forum Index Johan! If you have pictures of the other five lifers in your signature, they also deserve a place on the Index! :dance: :dance:

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arks
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Re: Oystercatcher, Eurasian

Unread post by arks » Sun Nov 27, 2016 4:05 am

Fascinating details, JvR!
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