THE UNDERLYING IDEA 61 
so-called English sparrow. This little creature, re- 
ceived at first with such joy, soon became the object 
of an almost bitter hatred on the part of very many 
people. This is really due to the fact that this bird is 
one of nature’s darlings and thoroughly succeeds 
where it has an even chance. 
The number of birds of any particular species which 
a region will support seems to be fairly definite. If a 
species is especially protected until it becomes unusu- 
ally abundant, the removal of the protection commonly 
brings it down promptly to its original numbers. On 
the other hand, an accident of severe character or a 
special persecution may much diminish the number of 
the species, and still it will, within a comparatively 
few years, return to its previous abundance. 
The inhabitants of Florida who own orange groves 
will never forget the winter of ’94-5. A bitter cold 
wave swept along the coast and killed such large num- 
bers of orange trees as almost to cut Florida out of the 
orange market and to open the gate to California, 
who was eagerly offering her fruit. This same frost 
caught the migrating blue birds and killed them by the 
thousands. When spring came bird-lovers throughout 
the eastern United States found an astonishing scar- 
city of these favorites. It was feared that with num- 
bers so small they could not possibly compete with 
their enemies and with whatever untoward circum- 
