Circus aeruginosus, commonly known as the Western Marsh Harrier, is a bird of prey found in Europe, Asia, and Africa. The word "circus" in its name refers to its genus, which scientific classification group it belongs to. However, there are many synonyms for the word "circus aeruginosus" that people use to refer to this bird. Some of these synonyms include the Harrier, Marsh Harrier, Eurasian Marsh Harrier, Montagu's Harrier, and Hen Harrier. These synonyms can help people communicate about the bird without using its scientific name, making it easier for people of all backgrounds to talk about this magnificent creature.