Avian Introductions—F isher 
61 
species transported to a more equable climate 
may show an increased length of breeding sea¬ 
son; it may nest several times in a year and may 
be more successful in raising its young. The 
Kentucky Cardinal ( Richmondena cardinalis) 
is a good example; in the Territory of Hawaii 
this bird breeds throughout the year, and a 
single pair has been known to rear three broods 
in a year, compared to one or sometimes two 
broods in continental United States. Its num¬ 
bers are increasing remarkably. Other species 
show similar trends. Not only is the longer 
season important in raising the breeding poten¬ 
tial. In their native countries most of the species 
are partly limited by the amount of food avail¬ 
able and by the number of species using them 
as prey. With an abundant food supply for 
many different species, as in Hawaii, and the 
possibility of birds adapting their food habits to 
the more easily obtained foods, there is a dis¬ 
tinct probability of enormous increases in the 
populations of certain species. This may not be 
desirable. 
In the islands there is no avian predator to 
help control the populations; the only hawk 
(Buteo solitarius ), which does not feed on birds 
except occasionally, is limited to the island of 
Hawaii, and is present in such small numbers 
that it is ecologically unimportant. The Short¬ 
eared Owl (Asio flammeus sandwichensis) is a 
possible predator. It is thought to feed primarily 
on mice, but its food habits are largely un¬ 
known. The only other vertebrate animal species 
available to prey on young or adult birds or 
their eggs are: feral cats, dogs and hogs, the 
native rat ( Rattus hawaiiensis ), which is not 
numerous, several exotic species of the family 
of Old World mice and rats which are cosmo¬ 
politan, and the many mongooses ( Herpestes) 
which have to a great extent failed to accom¬ 
plish the purpose for which they were imported, 
that is, to keep the rat populations at a minimal 
level. There are those who maintain the mon¬ 
goose is the major factor keeping the rats under 
control, but field observations indicate that large 
numbers of rats and of mongooses are present 
in the same areas. The tendency of rats to spend 
more time in trees may have been occasioned 
by the activities of the mongoose. Because of 
this tendency to live in trees, the rats are now 
more of a menace to the tree-nesting birds; 
formerly their predatory activities were more 
or less restricted to ground-nesting birds. Aside 
from this, the mongoose is probably the most 
important control on ground-nesting birds in 
Hawaii. This theory is attacked by those who 
have examined stomachs of the animal on the 
grounds that they do not usually find feathers 
or remains of eggs in the stomachs. A study of 
the feeding habits of the mongoose has shown 
the inadequacy of such an argument because the 
mongoose never eats the shell of an egg, and in 
eating birds it makes only one or two small 
openings in the carcass, works through these, 
and leaves the outside of the bird ruffled but 
practically intact. Considering this method of 
feeding, one could not expect to encounter 
numerous feathers in the stomach of the mon¬ 
goose. The workers who studied the stomach 
contents do not mention in their unpublished 
studies the fate of the ground-nesting birds of 
Jamaica when the mongoose was introduced, 
but they do cite the success of the mongooses in 
helping to control the rats there. 
Whether or not the mongoose fulfilled the 
promises of its importers, we now have rats and 
mongooses in abundance on the main islands, 
except on Kauai, Niihau, and Lanai, where the 
mongoose was never liberated. Both animals 
exert a depressing effect on the population of 
birds. 
Avian diseases also aid in controlling num¬ 
bers of birds, but we know practically nothing 
of these in Hawaii. Avian malaria has been 
found in the exotic Red-billed Leiothrix ( Leio - 
thrix lutea lutea) in Hawaii (Fisher and Bald¬ 
win, 1947: 51). We cannot say definitely that 
this disease was first introduced with imported 
birds, but the evidence seems to point that way; 
nor can we say definitely that the native birds 
have been adversely affected by malaria. For 
most animals imported into the Territory a 
