. Essentials of biology presented in problems. Biology. 300 THE VERTEBRATE ANIMALS two behind. Hawks and eagles are provided with strong talons with which the prey is seized and killed. Adaptation for semiaquatic life is seen in plovers, herons, or storks, where long legs and long toes enable the birds to seek their food in soft mud among reeds or lily pads, or along sand flats. True aquatic birds, on the other hand, are provided with webbed toes. The foot of the common barnyard duck, for example, is much like that of the alligator. In the ostrich and cassowary the wings are not used for fligh
. Essentials of biology presented in problems. Biology. 300 THE VERTEBRATE ANIMALS two behind. Hawks and eagles are provided with strong talons with which the prey is seized and killed. Adaptation for semiaquatic life is seen in plovers, herons, or storks, where long legs and long toes enable the birds to seek their food in soft mud among reeds or lily pads, or along sand flats. True aquatic birds, on the other hand, are provided with webbed toes. The foot of the common barnyard duck, for example, is much like that of the alligator. In the ostrich and cassowary the wings are not used for flight; here the lower limbs have taken up the function of rapid motion. Perching. — The habit of perching is an interesting one. In many perching birds the tendons of the leg and foot, which regulate the toes, are self-locking; while asleep such birds hold themselves perfectly. A certain part of the ear, known as the semicircular ca- nals, has to do with the function of balancing. In the flamingoes and other birds, which do not perch, balancing appears to be automatic; thus the bird is able to sleep when in an upright position. Tail. — The tail is sometimes used in balancing; its chief func- tion, however, appears to be that of a rudder during flight. Most birds have imder the skin of the tail a large oil gland, whence comes the supply of oil that is used in waterproofing the feathers in preen- ing. The Skeleton. — The skeleton combines lightness, flexibility, and strength. Many bones are hollow or have large spongy cavities. The bones of the head and neck show many and varied adaptations to the life that the bird leads. The vertebrae which form the frame- work of the neck are strong and flexible. They vary in shape and. Skeleton of a fowl: C, clavicle; CV, cervical vertebrae; K, keeled ster- num ; PG, pelvic girdle; PcG, bones of pectoral girdle (except clavicle).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1911
