I think it may be helpful to understand why some feeds are appropriate for some ages and species and others are not. It basically reflects the nutritional makeup of the foods they eat in nature and those nutrients reflect what they genetically have become predisposed to.
Game birds, specifically quail, turkey, partridge, etc. in nature, hatch in the spring and early summer. Chicks and poults of those species eat primarily insects, other invertebrates and small vertebrates. That is a very high protein diet. As they mature, their diets shift to more seeds and greens - much lower in protein.
Chicken chicks in nature, on the other hand, eat a wider variety of foods including insects but also seeds and greenery. That more varied diet is lower in protein. All young growing birds require a higher level of crude protein and more importantly a comple array of essential amino acids than maturing birds and adults that are no longer growing.
Those differences in a natural diet are why game bird starter feeds are in the neighborhood of 28-30% protein while chicken starter ranges from 18-20% protein (a tad higher for meat birds for rapid growth). The dietary protein needed, continue to decline with age as their natural diet would transition.
The same can be said about ducklings and adult ducks. Many species of ducks eat mostly insects in spring and summer when those foods are most plentiful and provide the best nutrition for growing ducklings. When the seasons change and insects aren't as common, however, ducks will switch their diet to more easily available foods.
Since adult game birds eat mostly seeds and other types of vegetation, depending on the season, maintenance feeds can be as low as 12 or 13% protein.
Calcium to phosphorus ratio is important. Most birds do well on about 1% calcium and 0.5% phosphorus. Only birds actively laying eggs (i.e. building shells) can make use of the approximately 4% calcium in layer feed.