**7. Leg and foot musculature**

Owls have developed extremely specialised and powerful musculature in their legs and feet. Contrary to the visual image of an owl at rest, owls have relatively long legs; in some species, they can be as much as half the total body length. In flight, the legs are tucked under the body with the toes closed. Once the prey has been located, however, the owl will swoop down on the prey with its head forward and its feet swinging like a pendulum until the last moment before impact when its head is thrown back and its legs stretched out with its talons open. The eight toes are spread, just before contact, into a symmetrical configuration to cover as large an area as possible [3, 13].

Hind limbs of owls are characterised by the absence of some muscles found in other birds. They lack *m. iliofemoralis, m. ambiens*, both portions of *m. flexor cruris lateralis*, *m*. *plantaris*, and *m. fibularis longus* [29]. They also have a relatively short tarsometatarsus and the presence of well-developed sesamoids [30] and a specialised tendon locking mechanism [31]. These anomalies in the morphology of the owl's hind limb are associated with adaptations to catch, seize, keep, and kill the large prey [32]. As the owl's normal method of dispatching prey is by impact and constriction (a bite to the neck or skull may also be employed with larger prey), the musculature of the feet and toes are exceptionally powerful. Owls generate more force than Hawks and Falcons when closing their talons, which anatomically translates into stronger digit flexor muscles, more robust bones, and stronger tendons with ossification [28]. Owl's talons are more uniform in size amongst digits, generally less curved, and relatively larger than in diurnal raptors, which probably serve to maintain the reach of the toe for grasping [29].

Owls' feet have extremely thick pads with very prominent papillae (**Figure 12**). Unlike other birds, owls have cone-like papillae, free from one another [33]. The most extreme and specialised papillae are found in the fish-eating owls, where the distance between the papillae is comparatively long and the top sharply pointed [33]. These long-pointed papillae or spicules, help the owl to seize slippery fish and other aquatic prey. The dermal layer in the pad is thick and has a dense structure of collagenous fibres. The dermis functions as a base for the papillae and is the structurally firm part of the skin. The important function of the papillae is to penetrate the roughness of the ground, tree branches, or the fur and skin of prey [34].

Owls are *anisodactylous*, having three toes projecting forward and one toe projecting backwards. However, owls should perhaps be classed as *semi-zygodactylous*, as the outer toe is 'hinged' and can be moved backwards to give the owl's feet two toes projecting forward and two toes projecting backward configuration (*zygodactylous*). This configuration is ideal for perching on branches and seizing prey with cylindrical-shaped bodies (as in rodents) and also allows all four digits to maintain comparable locking power [29]. The anisodactyl configuration allows the owl greater stability on flat surfaces, such as nests, or when subduing larger, struggling prey on the ground. This hinged toe mechanism is not unique to owls as it is shared with the Osprey (*Pandion haliaetus*). The middle toe of the Tytonidae family of owls (Barn, Bay and Grass Owls) have a pectinate talon; a serrated, comb-like flange, used to groom the delicate facial auricular feathers (**Figure 12**). This is another feature shared with the Osprey (*Pandion haliaetus*).

**Figure 12.** *The foot of a barn owl (*Tyto alba*) shows pads and pectinate talon. Photo: Alan Sieradzki.*
