I spotted a black bird with red patches on its wings, it must be a red-winged blackbird.

red-winged 是由形容词 red（红色的）和名词 wing（翅膀）加上后缀 -ed 组成的复合形容词，字面意思是"红翅膀的"。 red-winged blackbird 指翅膀上有红色斑点的黑鸟，学名为"红翅黑鹂"，是北美常见的一种鸟类。