269 
Humming-birds of Guatemala . 
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 during 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 months 
when the Humming-birds of Guatemala usually appear to build, 
they are not the only ones. In 1858 I found a nest of C. 
cyanoccphala 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 different 
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 difference, however, exists in the bill, 
that of the male having much more of the brilliant coloui, fiom 
which the species takes its name, in the upper mandible. 
In the young bird the upper mandible is black. In speakin Q 
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 othei specie^, 
as in Chlorostilbon osberti , Heliopcedica melanotis , Amaziha rieffcn 
and A. dumerillii, Lophornis Helena, Cyanomyia cyanocephala, &c.; 
and I think it more than probable that wheie the bill o a c.i 
u 2 
