What is "cistothorus"

Cistothorus is a genus of birds in the Troglodytidae family. It contains the following species:

• Apolinar's wren, Cistothorus apolinari
• Mérida wren, Cistothorus meridae
• Marsh wren or long-billed marsh wren, Cistothorus palustris
• Sedge wren, short-billed marsh wren or grass wren, Cistothorus platensis