Insects such as crickets, mealworms and roaches are very high in chitin. When captive shamas are given the choice, they tend to pick out softer bodied insects that have lesser chitin, such as white mealworms that had just shed the skin. Although there is insufficient evidence to support my suspicion that the varieties of invertebrates that the shama will consume in the wild are overall much lesser in chitin compared to the insects fed to them in captivity, I am nevertheless quite convinced from many years of observations that the captive shama cannot be at its best when fed with a diet high in chitin or dietary fiber. I often see shamas showing signs of unwell and sometimes quite fluffed up after consuming large amounts of crickets and mealworms. Also, when fed for some time with a diet consisting of large amounts of crickets and mealworms, their appetite may decrease, prompting me to suspect that the large amount of chitin from these insects may cause some degree of impaction of the crop in captive shamas. Apart from my observations, there are also other reasons that led me to believe that a diet consisting of large amounts of chitin and dietary fiber may be quite unsuitable for the captive shama.
1) We do not know for sure whether or not the shama is able to produce chitinase enzymes but the fact that they regurgitate most of the indigestible chitin seems to suggest that chitinase activity is minimal even if it is present in the shama.
2) Unlike the graminivorous birds (grass eating) and folivorous birds (leave eating), the anatomy and physiology of the digestive tracts of insectivores like the shama are more suited to nutrient-compact diets with easily digestible fat and protein, utilizing these nutrients through an autoenzymatic type of digestion (by the enzymes produced from certain organs of the bird). The herbivorous birds on the other hand, have a digestive system relying partly on alloenzymatic digestion (by enzymes of microbial origin or fermentation) through which they are able to utilize the high fiber in their diet. It therefore appears to me that chitin and dietary fiber serves no nutritional purpose in the diet of the captive shama. Until they are regurgitated, large amounts of chitin or indigestible fiber in the crop could cause some degree of impaction which may also affect the appetite, as was often observed by me. They also dilute the nutrients of the diet and could quite possibly interfere with the digestion as well.
Keeping the above in mind, I had for quite some time now, avoided feeding large amounts of insects that are high in chitin. When it comes to feeding insects as part of their daily diet, I now feed crickets only sparingly and I would only use white mealworms. In order to substitute for the animal protein that may be lacking in this diet with very little live food, I have included substantial amounts of lean beef, sardines and eggs in my home-made pellets. Through many years of trials and errors, I have found these three sources of animal protein to be very good for the shama. As far as I know, my home-made pellets are also low in dietary fiber. My shamas rarely regurgitate.
Even during the molt, my birds are fed with very little live food and judging from the feather condition of the tails upon completion of their molt, this diet seems to be sufficient in animal protein. I have often been asked by my bird keeping friends how I had managed to keep my caged shamas in good and tight-feathered conditions most of the time, even during the molt. I would think that this is due to their nutrient-compact diet which is low in chitin, low in indigestible fiber and high in animal protein.
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