BIRDS OF NEW YORK 341 



are vigorous flyers, spending most of their time in the air hawking for 

 insects over rivers, lakes and fields, capturing their prey while on the wing. 

 They are more or less sociable in habits, sometimes immense colonies 

 associating together on their breeding ground. The nests of some species 

 were originally affixed to cliffs, but now they have availed themselves to 

 a considerable extent of structures erected by man; while those which 

 formerly nested in hollow trees accommodate themselves to boxes erected 

 for them; and even the Bank and Rough- winged swallows resort to gravel 

 pits and masonry, whereas formerly they were confined to the shores of 

 lakes and streams. As the migration season approaches, swallows gather 

 in immense numbers on chosen roosting sites where various species may 

 be found associating together, and separating again in the morning to 

 seek their food over the surrounding country. During the day they fre- 

 quently gather in companies of hundreds and thousands on the roofs of 

 barns and on telegraph wires or on the reeds of extensive marshes. These 

 congregations usually last until the end of August or the first weeks of 

 September when the swallows suddenly disappear and are not seen again 

 till the following April. Swallow roosts are usually found in the tall reeds 

 or flags of marshes where there is an expanse of many acres, or in thickets 

 of willows or alders. I have seen tens of thousands of Tree swallows 

 gathered on the Montezuma marshes to roost, and in thickets of the French 

 basket willow I have observed as many as twenty thousand swallows in 

 a roost which covered only two acres. The birds gather upon these roost- 

 ing grounds late in the afternoon, usually after sunset, and I have seen 

 a few belated arrivals come into the roost an hour after sundown. Swallows 

 are birds of cheerful disposition, continually twittering to each other as 

 they sit on telegraph wires or flit about over the ponds and streams or 

 over the meadows. Their flight is the personification of ease and elegance. 

 At the same time, they are very beneficial by destroying countless hordes 

 of insects. Some maintain that beneficial hymenoptera as well as some 

 of the predaceous coleoptera are destroyed, but the percentage is com- 

 paratively small, as shown by the examination of stomach contents. We 



