212 BIRDS OF LA PLATA 



thing for two species so closely allied to be found 

 inhabiting the same district* In both birds the 

 colours are arranged in precisely the same way ; but 

 the chestnut tint on S* albescens is not nearly so 

 deep, the browns and greys are paler, and there is 

 less black on the throat* 



I am pretty sure that in Buenos Ayres it is 

 migratory* and as soon as it appears in spring it 

 announces its arrival by its harsh* persistent* two- 

 syllabled call* wonderfully strong for so small a bird, 

 and which it repeats at intervals of two or three 

 seconds for half an hour without intermission* When 

 close at hand it is quite as distressing as the grating 

 song of a Cicada* This painful noise is uttered while 

 the bird sits concealed amid the foliage of a tree, 

 and is renewed at frequent intervals* and continues 

 every day until the Spine-tail finds a mate, when all 

 at once it becomes silent* The nest is placed in a 

 low thorn-bush, sometimes only two or three feet 

 above the ground, and is an oblong structure of 

 sticks, twelve or fourteen inches in depth, with the 

 entrance near the top, and reached by a tubular 

 passage made of slender sticks, and six or seven 

 inches long* From the top of the nest a crooked 

 passage leads to the cavity near the bottom ; this 

 is lined with a little fine grass, and nine eggs are 

 laid, pear-shaped and pale bluish-white in colour, 

 I have found several nests with nine eggs, and there- 

 fore set that down as the full number of the clutch, 

 though I confess it seems very surprising that this 

 bird should lay so many* When the nest is ap- 



