Answer: On the black, forked tail and wings-- a long section-- it has a sheen.
Explanation: With some changes to the punctuation, it is possible to create a sentence of sorts with the given words and phrases.
It is difficult for me to imagine this sentence-- apparently a description of a bird-- in a published report.
As you see, the use of dashes makes it possible to insert phrases that break the normal grammatical pattern of a sentence.
