Which physical feature, often called *oorbellen*, was key to the Kooikerhondje's success in luring ducks?

Answer

Long, feathered black tufts of hair on their ears

One of the most distinguishing features key to their luring success are the long, feathered black tufts of hair on their ears, which are known as *oorbellen*.

Which physical feature, often called *oorbellen*, was key to the Kooikerhondje's success in luring ducks?
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