Hummhig-hirds of Guatemala . 269 



other species^ in order that^ when the young birds make their 

 first essay to provide for their own sustenance, the flowers of the 

 forests and plains should be in greatest abundance. Hence, 

 perhaps, it is that September is the month daring which the 

 Humming-birds of Guatemala are principally engaged in incu- 

 bating their eggs and rearing their young, — a time when the 

 young of other birds have long been able to shift for themselves. 

 Perhaps also it would appear that a certain amount of experience 

 is necessary for the young Humming-birds to obtain a regular 

 supply of food, and that to gain this experience it is also neces- 

 sary that the showy flowers should be in bloom to attract atten- 

 tion, enabling them with greater ease to obtain the requisites of 

 life, until they learn where else their insect prey is to be found 

 among the leaves and shoots. 



Though September and the end of August are the mouths 

 when the Humming-birds of Guatemala usually appear to build, 

 they are not the only ones. In 1858 I found a nest of C. 

 cijanocephala in June, and in 1859 one in July, and again a nest 

 of A. corallirostris in December. 



Other birds show extreme irregularity in their breeding seasons, 

 so much so that one might birds'-nest all the year round. No 

 suppositions respecting the seasons of two places deduced from 

 the fact of the same bird being found breeding in two difi'erent 

 months, can be safely inferred, the difference being so great in 

 the same place. 



My specimens of A. corallirostris, though not in excellent 

 plumage, I think show that, as far as the feathers are concerned, 

 the sexes are alike. A diff'erence, however, exists in the bill, 

 that of the male having much more of the brilliant colour, from 

 which the species takes its name, in the upper mandible. 



In the young bii'd the upper mandible is black. In speaking 

 of this colouring of the bill, I may mention that it appears to be 

 due to the transparency of the outer film of the bill allowing 

 the blood to show through, and not to any especial colouring- 

 matter. This seems to be the case also in many other species, 

 as in Chlorostilbon osberti, Heliopcedica melanotis, Amazilia riefferi 

 and A. dumerillii, Lophornis lielence, Cyanomyia cyanocephala, &c. ; 

 and I thiidt it more than probable that where the bill of a dried 



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