Differentiating between heterophils and eosinophils in avian species can be a challenge even for the experienced observer. While it is well-known that heterophil granules are traditionally rod-shaped and eosinophil granules are more rounded, it can be a difficult distinction to make in practice.Thankfully, our Psittacine friends make it much easier on our tired eyes! Did you know that their eosinophil granules aren’t usually pink at all? Contrary to other birds, the granules of Psittacine eosinophils more commonly occupy the spectrum ranging from pale grey to bright blue! Above is an example of a particularly delightful blue eosinophil with unusually large granules from a 29-year-old Blue-fronted Amazon parrot.