Baldness in mynas

 Every now and then one is bound to come across a bald-headed myna, especially in a Common Myna.  

"... Despite the common occurrence of bald-headed Common Mynas, very little is known on its cause.  Moulting, fighting, nutrient deficiencies, and mites could be some of the causes that may contribute to the shedding of feathers...." (extract of Bird Ecology Study Group)

And further on, I came across this Javan Myna that looked like it had its little crest torn off, or was this the beginning of a balding?

And against its normal kindred avian kind.