SWIFTS, GOAT-SUCKERS, MUNI AS, ETC. 253 



over the lawns, every now and then uttering the 

 peculiar call from which their common name is 

 derived because of its likeness to the sound made 

 by any small hard object skimming over the sur- 

 face of a frozen pond. Their flight is admirable 

 in the ease and grace of its sudden evolutions, 

 especially when the birds were projected against 

 a silvery grey evening sky, or wheel and flutter on 

 a background glorified by the flaming tints of a 

 tropical after-glow. They often interrupt their 

 aerial excursions in order to descend to the ground, 

 especially where the surface is traversed by a dry 

 and dusty highroad abounding in the droppings of 

 horses and cattle that harbour stores of insect-food. 

 They will often remain sitting in such places for 

 some time, resting quietly and presenting a very 

 strange appearance, owing to the way in which they 

 squat closely flattened down on the surface. Their 

 flight as " they float and run " through the 

 air is more butterfly-like than that of almost any 

 other bird. It consists of an alternation of short 

 quick flappings, two or three in succession, with 

 periods during which they sweep onwards on widely 

 extended wings that show conspicuous patches of 

 brilliant whiteness on their under surfaces. All 

 through the cold weather their characteristic cries 

 are to be heard sounding out into the night, but 

 they are rarely audible in summer or autumn. 

 Besides their ordinary subdued call they can utter 



