18/G.] MR. W. H. HUDSON ON THE HABITS OF RAILS. 107 



hurriedly repair to the customary spot. In a few moments, and 

 almost simultaneously, the birds appear, emerging from the reeds 

 and running into the open space, where they all immediately whirl 

 about and begin the exhibition. 



Whilst screaming they rush from side to side as if possessed with 

 frenzy, the wings spread and agitated, the beak wide open and 

 raised vertically. I never observed them fight or manifest anger 

 towards each other during these performances ; and, knowing the 

 pugnacious spirit of the Ipicahas, and how ready they are to seek a 

 cpiarrel with birds of other species, this at first surprised me ; for I 

 was then under the mistaken impression that these gatherings were 

 in some way related to the sexual instinct. 



Whilst watching them I also remarked another circumstance. 

 When concealing myself amongst the rushes I have been compelled 

 to place myself so disadvantageously, owing to the wet ground, that 

 any single bird straying accidentally into the open space would have 

 discovered my presence immediately ; yet the birds have entered and 

 finished their performance without seeing me ; so carried away are 

 they by the emotion that possesses them during these moments. 

 But no sooner has the wild chorus ended than, aware of my pre- 

 sence, they have fled precipitately into the reeds. 



How could this curious habit I have described, and which cannot 

 be considered advantageous, have originated 1 It is simply that this 

 species has a somewhat singular way of giving expression to an in- 

 stinctive feeling common to all creatures. Many birds and mammals 

 have social gatherings, peaceful like those of the Ipicaha ; and if seen 

 to fight, these are but playful engagements ; for the emotion that calls 

 them together is a joyous one. It manifests itself so variously in 

 different species that a person might easily be led to believe that the 

 displays he observes are, in many instances, inspired by the sexual 

 passion. 



The Ibis melanotis, the Glossy Ibis, the Black-collared Himanto- 

 pus, and the Spurred-winged Lapwing also hold similar exhibitions. 

 The last-named species has a far more remarkable performance on 

 the ground, aptly called " dancing " by the Argentine peasants ; for 

 the birds, in twos and threes, run and whirl about and stand bowiug 

 till their beaks touch the ground, all the time regulating their move- 

 ments to drumming rhythmic notes. 



The Chimangos (Milvago) frequently have meeting-places where 

 they circle about, sportively quarrelling in the air, then rest, each 

 one on his separate perch ; and at intervals one bird utters a long and 

 song-like cry, followed by a succession of short notes, in which all 

 the birds join as in a chorus. 



Males and females of many species in which the sexes are always 

 faithful sing and scream together in a jubilant manner at intervals 

 through the day. This habit is most remarkable in the Oven-bird 

 (Furnarius) : these stand together facing each other, singing their 

 shrill excited song, all the while beating their outspread wings in 

 time with the notes, and each bird taking a part, so that the per- 

 formance produces the effect of harmony. 



