MIGRATION AND FLIGHT. 87 



time of their usual journeys either to or from the fens, the 

 whistling sound of thousands of wings, or the shrill notes of 

 call by which these vast flights are kept together in the dark- 

 ness of night, may be heard overhead. 



Birds, too, in their longer flights, no doubt avail themselves 

 of different currents in the air ; for we know that often, when 

 the lower stream of air is blowing from the west, another 

 stream far above may be blowing from another direction ; this 

 may be frequently seen by the motion of the upper clouds 

 moving in contrary directions from those at a lower level 

 Those most beautiful of all the feathered race, the Birds of 

 Paradise (not only distinguished by their brilliant plumage, 

 but from their being singularly decorated with tufts or trains 

 of light, loose, fringy feathers, which render it difficult for 

 them to fly, excepting against the wind, which smooths them 

 down), are chiefly natives of a few islands in the Indian 

 Ocean, and when sailing between these islands, flocks of them 

 are often seen crossing, and always flying against the wind ; 

 but as in that climate sudden squalls often occur from an 

 opposite quarter, the birds, when caught by them, are observed 

 immediately to dart upwards till they ascend beyond the 

 reach of the gale, and are then seen to pursue their course as 

 before. 



One other very remarkable fact connected with these long 

 journeys undertaken by birds over seas and lands, is that they 

 are gifted with some secret power, enabling them not only to 

 find their way to and from the distant countries they visit, 

 but actually guiding them to the very same place from whence 

 they came, and the very same spots for building their nests. 

 This has been proved by marking the claws of Swallows, 

 which were in the habit of building in sheds or outhouses, 

 where they could easily be retaken on their return in the 

 spring, and examined. An instance came under our own 

 observation, of a pair of Swallows returning to build for three 

 years in a small closet in a school-house, entering by a broken 

 pane in the casement, and forming their nests in a corner above 

 ihe window : and as they were never disturbed, the female 



