18,"!.] MR. W. H. HUDSON ON THE BIRDS OF BUENOS AYRES. .'5'27 



"The Hirundo leucorrhoa is the most common of our Swallows, 

 and in its glossy coat of deep blue and green, with rump and under- 

 plumage snowy white, is an elegant and beautiful bird. They are 

 the last of all the migratory species to leave us in autumn, and in- 

 variably reappear in small numbers on every warm day in winter, so 

 that some people do not believe that they leave us at all, but only 

 retire to the more sheltered places when the weather is severe. In 

 the winter of 1869 I saw three of them skimming over the plain on 

 one of the coldest days I have ever experienced ; the thermometer 

 having stood at 29°Fahr. the preceding evening. But those that 

 remain through the winter with us are apparently only a few indi- 

 viduals, while in the autumn myriads are seen passing north in their 

 migration, and some years continue passing for upwards of a month. 

 In April 1869, several days after all the Swallows of our five species 

 had totally disappeared, flights of the kind I am describing began 

 again to appear passing north ; and for ten days afterwards they con- 

 tinued to pass. They would descend to sip water from a pool where 

 I watched them, alighting afterwards on the reeds and bushes 

 to rest. Many of them appeared quite tired with their journey, 

 rising reluctantly when approached, and some allowing me to stand 

 within two yards of them without flying. I had never before ob- 

 served any supplementary or later migration like this ; and last 

 autumn (1870) certainly nothing of the kind took place. Probably 

 the migration of this species extends very far south ; at present they 

 are passing in great numbers, and have been so passing for the last 

 fifteen days. 



"They sometimes build in a tree, in the large nest, previously aban- 

 doned, of the Seiiatero (Anumbius acuticaudatus). I have had 

 occasion before, and shall have it again in descriptions of other 

 species, to mention that interesting bird and its great nest. 



" It is, however, under the eaves of houses that these Swallows 

 principally breed ; and there is not a house on the pampas, however 

 humble it be, but some of these birds are about it, sportively skimming 

 over and about the roof or curiously peering under the eaves and 

 incessantly uttering their gurgling, happy notes. Indeed their 

 fondness for being close to a house is so remarkably strong that in 

 their longest excursions they are seldom more than five minutes 

 absent from it. 



" For a month or six weeks before they begin to build, they seem to 

 be holding an incessant dispute ; and however many eligible chinks 

 and holes there may be, the contention is always just as great among 

 them, and is doubtless referable to opposing claims to the best places. 

 The excited twittering, the constant striving of two birds to alight on 

 the same square inch of wall, and the chases they lead each other round 

 and round the house, that always end exactly where they began, tell 

 of clashing interests and great unreasonableness on the part of some 

 among them. By-and-by the quarrel takes a more serious aspect ; 

 apparently every argument of which a Swallow is capable has been 

 exhausted, and a compromise more impossible than ever, and so 

 fighting begins. Most vindictively do the little things clutch each 



