212 THE BIOLOGY OF BIRDS 



(Ceriornis) has a fleshy blue horn above each eye and a 

 large gular wattle. In his courting excitement he erects 

 the horn and inflates the wattle. In the male Tanagers of 

 the genus Procnias, inhabiting wooded country in Tropical 

 America, there are long thread-Hke or papilla-like out- 

 growths of skin on the forehead and on the root of the bill 

 (see Meisenheimer, 1921, p. 448). 



As to plumage, we may think of the peacock's crown 

 and of the exuberant exaggeration of the tail-coverts which 

 conceal the true tail-feathers or rectrices. There may be 

 crests, ear- tufts, ruffs, neck-capes, hackles, breast-bristles, 

 and so on, in most cases absent or unrepresented in the 

 females. The pigmentation may be different in the two 

 sexes, but in many cases the difference is not so great as it 

 seems, for it is largely due to the physical structure of the 

 surface of the feather. Very common is the elongation and 

 specialisation of certain tail-feathers, sometimes only t^vo, 

 which may consist almost wholly of a very long rhachis or 

 may have an expanded decorative disc at the end of this. A 

 very extraordinary case is seen in four-year-old male Lyre- 

 birds (Menurus) which have " the exterior pair of feathers 

 curved like a lyre, with very narrow outer and very broad 

 inner webs ; the next six pairs have verj' distant barbs 

 and no barbules, except towards the base ; while the two 

 median plumes have narrow inner and no outer webs, and 

 after crossing below, curve boldly outwards. The female 

 has a long, broad, normal tail, the median feathers exceeding 

 the rest " (Evans, 1899, p. 491). In ordinary daily life, the 

 cock keeps his tail horizontal ; in his courtship excitement 

 it is erected and the wings droop. As he struts and pirouettes, 

 he sings. He appears to be monogamous. 



In the male weaver-birds of the genus Vidua and some 

 related genera the four median feathers of the tail are greatly 

 elongated, but while they are broadened in some species 

 they taper to threads in others, or they may have a bare 

 shaft and a " racquet " tip. In another weaver- bird, 

 Pyromekena franciscana, the male puts on at the breeding 

 season a velvety " wedding garment," partly black and 



