218 The Naturalist in La Plata. 
from all competition with other birds as the solitary 
savage is removed from the struggle of life affect- 
ing and modifying men in crowded communities. 
The lower kind of competition affecting humming- 
birds, that with insects and, within the family, of 
Species with species, has probably only served to 
intensify their unique characteristics, and, perhaps, 
to lower their intelligence. 
Not only are they removed from that indirect 
struggle for existence which acts so powerfully on 
other families, but they are also, by their habits 
aud the unequalled velocity of their flight, placed 
out of reach of that direct war waged on all other 
small birds by the rapacious kinds—birds, mammals, 
and reptiles. One result of this immunity is that 
humming-birds are excessively numerous, albeit such 
slow breeders; for, as we have seen, they only lay 
two eggs, and not only so, but the second egg is 
often dropped so long after incubation has begun 
in the first that only one is really hatched. Yet 
Belt expressed the opinion that in Nicaragua, where 
he observed humming-birds, they out-numbered all 
the other birds together. Considering how abun- 
dant birds of all kinds are in that district, and that 
most of them have a protective colouring and lay 
several eggs, it would be impossible to accept such 
a statement unless we believed that humming-birds 
have, practically, no enemies. 
Another result of their immunity from persecu- 
tion is the splendid colouring and strange and 
beautiful feather ornaments distinguishing them 
above all other birds; and excessive variation in 
this direction is due, it seems to me, to the very 
