Comparative protein requirements of three species of parrots with distinct dietary specializations

Highly specialized nectarivorous and frugivorous birds have overcome the constraints of low dietary protein levels. Proposed physiological mechanisms that enable such specialists to subsist on low-protein diets include low protein requirements, low endogenous protein losses, high feed intake, and high protein digestibilities. These traits were compared among nectarivorous red lories (Eos bornea), frugivorous Pesquet’s parrots (Psittrichas fulgidus), and granivorous budgerigars...