. The structure and life of birds . ed itself to different modesof life. The normal number of toes is four, the fifthor little toe having been lost. The first, as a rule,points backward. The Emeu, the Rhea, and theCassowary have only three, having lost the first as Ostrich has only two, the third and fourth, and thelatter of these two is small and bears no nail. As inthe horse, it is the middle toe which carries all theweight. Among English birds the most strikingdifference is between the webbed feet of the swimmersand the separate-toed feet of the perchers, climbers,waders, and runne
. The structure and life of birds . ed itself to different modesof life. The normal number of toes is four, the fifthor little toe having been lost. The first, as a rule,points backward. The Emeu, the Rhea, and theCassowary have only three, having lost the first as Ostrich has only two, the third and fourth, and thelatter of these two is small and bears no nail. As inthe horse, it is the middle toe which carries all theweight. Among English birds the most strikingdifference is between the webbed feet of the swimmersand the separate-toed feet of the perchers, climbers,waders, and runners. The Gannet, the Cormorant, andtheir allies have all four digits connected by the web ;in most swimming birds the first is free. There are VI FORM AND FUNCTION 165 various intermediate stages before we arrive at separate-toed feet. In the Dabchick and the other Grebes, thetoes are not connected, but there is on cither side ofeach a broad expansion of skin. In the Kingfisherthe second, third, and fourth toes arc fastened together. Fig. of (i), Woodpecker ; (2), Grebe. for most of their extent. The Woodpeckers, Cuckoos,and Toucans have a most curious form of foot calledzygodactyle or yoke-toed, the first and fourth toespointing backward, the other two forward—a footspecially adapted for climbing. In the Swift all the 166 THE STRUCTURE AND LIFE OF BIRDS chap. toes turn forwards. The number of Phalanges orsegments in each varies very much in different the first toe has 2 ; the second, 3 ; the third,4 ; the fourth, 5. The Swift has in the respectivetoes only 2, 3, 3, 3. This and the extreme shortnessof his legs must account for his inability (if the inability,as is popularly supposed, exists) to rise from the Howard Saunders denies the correctness of thepopular belief, but I am not sure that the bird isnot in difficulties when he finds himself among grassof any length. Perching. Most of our common birds would soon fall victimsto some nocturnal
Size: 1486px × 1682px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookidstructurelif, bookyear1895
