To me, the most crucial factor affecting the success or failure in bringing out the best from the caged male white-rumped shama has always been the outcome of its annual molt.
A bad molt will almost certainly result in the bird not looking its best. A flawless physical appearance from a good molt on the other hand, is an indication at the least, that all is also well within.
There are other physiological changes that take place besides the renewal of feathers during an annual molt. The natural hormonal transition that takes place within the bird that is coming out of a good molt, will ensure that its form will peak. The rising testosterone level after a good annual molt is a natural occurrence in preparation for the breeding period that follows. A bird that goes through a good molt in the wild will be well prepared, with renewed feathers and vigor to face the challenges thereafter, which will come from competing for a mate and defending its territory. Thus, the annual molt is the underlying factor that determines how well the caged male shama will look and perform for the rest of the year until its next molt is due.
Grand Funk - Inside looking out