140 The Natural History 



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

 and therefore they are not capable of such 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 sur- 

 face 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 the twenty-first, and are never without unfledged 

 young as late as Michaelmas. 



As the summer declines the congregating flocks in- 

 crease 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 the third and sixth, 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 district where they are bred, 

 they must undergo vast devastations somehow, and some- 

 where ; 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. 



