“Ring-billed Duck” may be a better name for this species, as its neck ring is usually only visible at close range. The white ring on the bill is a prominent field mark.
Ring-necked Duck with visible neck ring (Aythya collaris, Fuligule à collier, RNDU) from my Better than Bosque workshop. Bosque del Apache National Wildlife Refuge, San Antonio, New Mexico, USA. Image Copyright ©Christopher Dodds. Sony Alpha alpha 1 Mirrorless camera & Sony FE 600mm f/4 G Master OSS Lens with Sony FE 2X Teleconverter @1,200mm ISO 1,600, f/8 @ 1/3,200s. Full frame image. Manual exposure.