Ryan P.G. (2013) Moult of flight feathers in darters (Anhingidae). ARDEA 101 (2): 177-180

There is little information on flight feather moult in darters (Anhingidae). I used a combination of direct observations and photographs to confirm that the normal pattern of moult is to replace all remiges synchronously, but not all rectrices. I surmise that at least some rectrices are retained year-round because they are important for controlling body angle and depth while diving in shallow water. However, a few birds do not replace all their remiges at once, retaining some inner primaries and secondaries. The retained feathers are insufficient to allow flight, and the reason why these feathers are retained is unknown.