Posted by Penelope Heinze (63.11.3.147--1cust147.tnt1.bismarck.nd.da.uu.net) on March 04, 2000 (or so) at 10:24:19:
As my female canaries reach breeding stage and start sitting on nests, they lose the feathers on top of their heads and neck. This happens when they are alone in the cage or with others. Some of the feathers grow back when the nesting season has stopped, but the females still retain some baldness on the top of the head. There is no other signs of illness, but one female has since died at age 2. The males do not lose any feathers.