2013 April Nature News – Talons and Beaks Mean Business

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Gail-Measuring-a-bald-eagles-beak-helps-determine-gender

Measuring a bald eagles beak helps determine gender

Different species have beaks suited to handling their particular prey group. The largest raptors such as bald eagles and golden eagles have impressively sized bills that allow them to tear into the hide of a large animal. Owls have relatively small beaks, as they often hunt prey that can be swallowed whole.

All members of the falcon family have a tomial tooth. This triangular extension of the outer edge of the upper mandible fits into a matching notch in the lower mandible. At the moment of attack, the tomial tooth slices between the vertebrae of the prey and severs the animal’s spine. This instant kill relieves the falcon of the difficulty of flying with a struggling victim. Peregrine falcons have a further adaptation related to their ability to capture prey in flight. Baffles within the nostrils of the peregrine regulate air entering the nasal cavity, and allow them to continue to breathe while diving after prey at speeds reaching 200 mph.

The overlarge feet and sharp curving talons of a raptor are the most dangerous aspect of the animal.  The powerful feet of a great horned owl can exert 80 pounds of pressure, and eagles are even stronger. Raptorial feet are heavily padded on the bottom and equipped with Herbst corpuscles.  These nerve endings increase the sensitivity of the bird’s sense of touch and cause the foot to clamp shut the instant it comes in contact with prey. Large flexor tendons in the toes close with a ratchet-like mechanism that allows a raptor to keep its feet clamped on its prey or a perch without effort. In this way, raptors can carry heavy prey items into a tree or back to their nest.

Members of the accipiter family (Cooper’s hawks, sharp-shinned hawks and goshawks) primarily hunt birds. Thus they are equipped with long toes that allow them to reach through plumage to the bodies of their victims. Peregrine falcons also have relatively long toes, as they use their feet to virtually knock their prey out of the sky in high-speed strikes.

Barn owls as well as members of the heron, bittern and nightjar families have a pectinate claw. This talon is scaled on the inner edge much like a comb and is used to preen feathers on the neck and head and also to clean bristles around the beak.

All owls and also osprey are zygodactyl, meaning they have an opposable toe. Other raptors have three forward-facing toes and one that faces back, the hallux. The zygodactyl birds can rotate the outermost front facing toe to the back, so that two toes face forward and two back. This allows great dexterity and a wider range of prey. The osprey also has sharply hooked talons and spicules on their toes, rough bumps like sandpaper that increase the bird’s ability to effectively carry a slippery, thrashing fish.

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