What is one of the peculiar, long, narrow feathers on the neck of fowls, most noticeable on the cock, -- often used in making artificial flies; hence, any feather so used called?

hackle — One of the peculiar, long, narrow feathers on the neck of fowls, most noticeable on the cock, -- often used in making artificial flies; hence, any feather so used. (Webster's 1913.)

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