Two undescribed species of bird from West Africa

Taxonomically undifferentiated western and eastern populations of Dusky Long-tailed Cuckoo Cercococcyx mechowi and Yellow-spotted Barbet Buccanodon duchaillui are known to have very different voices. The cuckoo has two song types, a melodious three-note whistle and a plaintive whinnying in West Africa west of the Bakossi Mountains in Cameroon, and a much less melodious, higher-pitched three-note whistle and a much faster whinnying in Central Africa east of the Bakossi Mountains.