With long tailed shamas, many things can go wrong during the growth of the pair of longest tail feathers:
1) Fret lines indicate insufficient intake of food during the period they were formed (this can also happen to short tailed birds).
2) Wavy tail feathers are caused by an improper diet (this can also happen to short tailed birds).
3) A scissors tail is usually caused by the shorter tail feathers coming in between the pair of longest tail feathers during the growing out period, causing the latter pair to be forced apart and altering the direction of their growth. This may sometimes be the result of vigorous tail play during the molt when the tail feathers are not yet fully grown. This condition is not seen on shamas in the wild. I have also suspected that a lack of humidity in the surrounding area during the molt may have also contributed to this condition in captivity. A cage that is too small can also contribute to this.
4) One or both of the longest tail feathers can sometimes grow out in an abnormal way. The entire feather is turned about 90 degrees with one edge of the affected feather facing upwards and the other facing downwards. The reason for this is unclear. Improper diet, follicle mites and lack of sufficient humidity could all be among the possible causes for this abnormal growth of the tail feathers.
5) One of the longest tail feathers may sometimes be permanently absent. This is sometimes caused by repeatedly pulling out the feather causing permanent follicle damage resulting in the feather being unable to be replaced.
