It's just plain common sense to realize that species native to drastically different ecological and environmental climates, each with vastly different food sources available, would have evolved with different nutritional needs.
Over the past few several years, it has been acknowledged that nutritional needs do vary by individual parrot species and, as a result, some manufacturers have developed species specific formulated diets. For example, low fat content for Amazons, higher fat content for Macaws, increased vitamin A for Eclectus and low iron diets for softbills.
There are ongoing studies to understand the requirements of various species but honestly, the science has a long way to go. Most of our knowledge of avian nutritional requirements has been developed from studies conducted on poultry....yes, chickens.
The basic nutrients needed are the same for all avian species, however, the source of the nutrients and levels required vary between species and even within a species depending on the status of the individual bird (i.e., age, activity level, breeding status, sex, health, size, environmental conditions, etc.)
Bird owners are encouraged to consult with their avian vet as well as to research the crops, fruits, nuts and other flora indigenous to the geographical area native to their species of bird. Armed with this knowledge, it is then possible to incorporate the most appropriate foods and supplements into their birds overall feeding plan.
Again, we would like to emphasize, that no one commercial diet comes close to simulating how our birds eat in nature and none of the commercial diets provide for 100% of the nutritional needs of our birds. We must arm ourselves with as much knowledge as possible about our birds, their native environment and to do the best we can to meet their needs by providing a well rounded selection of healthy foods.