NATURAL HISTORY OF SELBORNE. 171 



partook of the filth of that sooty atmosphere. Martins are by far 

 the least agile of the four species ; their wings and tails are short, 

 and therefore they are not capable of s-uch surprising turns and 

 quick and glancing evolutions as the swallow. Accordingly they 

 make use of a placid easy motion in a middle region of the air, 

 seldom mounting to any great height, and never sweeping long 

 together over the surface of the ground or water. They do not 

 wander far for food, but affect sheltered districts, over some lake, 

 or under some hanging wood, or in some hollow vale, especially 

 in windy weather. They breed the latest of all the swallow kind : 

 in 1772 they had nestlings on to October 2ist, and are never 

 without unfledged young as late as Michaelmas. 



As the summer declines the congregating flocks increase in 

 numbers daily by the constant accession of the second broods ; 

 till at last they swarm in myriads upon myriads round the villages 

 on the Thames, darkening the face of the sky as they frequent the 

 aits of that river, where they roost. They retire, the bulk of them 

 I mean, in vast flocks together about the beginning of October ; 

 but have appeared of late years in a considerable flight in this 

 neighbourhood, for one day or two, as late as November 3rd 

 and 6th, after they were supposed to have been gone for more 

 than a fortnight. They therefore withdraw with us the latest of 

 any species. Unless these birds are very short-lived indeed, or 

 unless they do not return to the districts where they are bred, 

 they must undergo vast devastations somehow, and somewhere ; 

 for the birds that return yearly bear no manner of proportion to 

 the birds that retire. 



House-martins are distinguished from their congeners by having 

 their legs covered with soft downy feathers down to their toes. 

 They are no songsters ; but twitter in a pretty inward soft manner 

 in their nests. During the time of breeding they are often greatly 

 molested with fleas. 



I am, etc. 



