The red-crowned crane (Grus japonensis) is a critically endangered species. Three-dimensional–printed prosthetic beaks made of titanium alloy and polyether ether ketone (PEEK) were used to repair the beak of a red-crowned crane that had a complete fracture of the anterior maxillary bone and rhinotheca. The physical properties and stability of the prostheses and changes in the crane's behaviors after application of either beak were evaluated. The titanium alloy and PEEK prosthetic beaks weighed 30.81 g and 5.9 g, respectively. Scanning electron microscopy showed differences in microstructure between the 2 materials and the true beak; the true beak was softer than both materials from which the prostheses were made. The titanium beak frequently detached, and the residual natural beak showed significant cuticle softening with this prosthetic beak. The titanium beak detached within an approximately 3-month period after placement, whereas the PEEK prosthetic beak has remained secure for 2 years. Moreover, the crane's foraging times (P < .01) and grooming times (P < .05) with the titanium alloy false beak were lower than the normal, red-crowned crane. With the PEEK beak, no detachment or cuticle softening occurred, and foraging and grooming behaviors were evaluated by the investigators as natural (P > .05). Based on the results of this clinical case, the PEEK prosthetic beak was found to be superior to the titanium alloy prosthetic beak in color, weight, firmness, and postoperative effects.