28 BIRDS OF LA PLATA 



themselves into words ; but unlike the other Swallows 

 the Martin has no set song. 



This Martin is never seen to alight on the ground 

 or on the roofs of houses, but solely on trees ; and 

 when engaged in collecting materials for its nest, it 

 sweeps down and snatches up a feather or straw 

 without touching the surface. It breeds only in the 

 clay ovens of the Oven-bird (Furnarins rufus). I at 

 least have never seen them breed in any other situa- 

 tion after observing them for many summers* An 

 extraordinary habit, for, many as are the species 

 that possess the semi-parasitical custom of breeding 

 in other birds' nests, they do not confine them- 

 selves to the nest of a single species excepting the 

 bird I am describing* It must, however, be under- 

 stood that my knowledge of this bird has been 

 acquired in Buenos Ayres, where I have observed 

 it ; and as this Martin possesses a wider range in 

 South America than the Oven-birds, there is no 

 doubt that in other districts it builds in different 

 situations. 



On arriving in spring each pair takes up its position 

 on some tree, and usually on a particular branch ; 

 a dead branch extending beyond the foliage is a 

 favourite perch. Here they spend much of their 

 time, never appearing to remain long absent from it, 

 and often, when singing their notes together, fluttering 

 about it with a tremulous, uncertain flight, like that 

 of a hovering butterfly. About three weeks after 

 first arriving they begin to make advances towards 

 the Oven-bird's nest that stands on the nearest post 



