154 Our Bird Friends. 



to the habits of their owners. In Eagles and 

 Vultures they have a rounded appearance, but the 

 feathers being long, the birds fly well, sailing round 

 and round in majestic circles and remaining in tlie 

 air for long periods of time with ease. Peregrine 

 Falcons, Swifts, and Swallows have narrow, pointed 

 wings, and fly with remarkable rapidity. In strong- 

 flying species the folded wing generally measures 

 twice the length of its owner's bod}', that is, taking 

 the distance from the breast to the root of the 

 tail. 



Wing area varies very considerably in relation 

 to the weight of the body to be carried. A French 

 naturalist has calculated that a Swallow weighing- 

 one pound would require the enormous wing area 

 of something like live square feet. The Australian 

 Crane flies well on half a square foot per pound ; 

 and if a man weighing twelve stone were thinking 

 of adopting flight as a means of locomotion, and 

 could go to a shop and order a pair of wings 

 on the very low basis of the Australian Crane, 

 each one would need to be fourteen feet long and 

 three broad, or double the area of an ordinary 

 room door. 



Wing beats vary in rapidity from about ninety 

 per minute in the slow-going Heron to an un- 

 countable speed. Even such birds as Seagulls 

 manage to get in as many as one hundred and 

 eighty strokes in a minute. Many species may be 

 distinguished at great distances by their methods 



