Improved anti-pecking devices, particularly for poultry and game birds, comprise a pair of limbs having end portions of reduced cross section which engage the nostrils of the bird or other animal, at least one bit member connecting the limbs, and a guard member which projects forwardly from the limbs beyond the end of the beak of the bird. The forward end of the guard may be split. The device may further include resilient bias members which bear upon the upper surface of the beak, in use. Other variations include guard members which extend laterally outwards from the sides of the limbs and multiple bit members spaced apart along the length of the device. The size and configuration of the device and its constituent parts may be varied to suit different sizes and species of bird. The devices are configured to be stackable, such that they may be stored in a cartridge or magazine for application using an automated fitting device.