Final answer:
The word 'plumage' in the selection refers to the covering of feathers on a bird, which is a distinctive and crucial characteristic of birds used for identification and behaviors like courtship.
Step-by-step explanation:
In the selection provided, the word plumage refers to the covering of feathers on a bird. The term describes the male cowbird's appearance, noting its 'chocolate hood and glossy green- black plumage,' which tells us that the bird has a distinctive set of feathers that are chocolate-colored near the head and glossy green-black elsewhere on its body. The use of 'plumage' in descriptions of birds is common, as feathers are an essential and characteristically distinguishing feature of avian species. For example, the golden-winged woodpecker's 'splendid plumage,' the cedar bird's 'little monteiro cap of feathers,' and the male bird species that use colorful plumage to attract mates, all highlight the importance of feathers in bird identification and behaviors such as courtship displays and territory defense.