PROTECTIVE ADAPTATIONS IN THE NESTING HABITS OP SOME CEN- 
TRAL AMERICAN BIRDS. 
BY MORTOlSr E. PECK. 
To the general rule that the struggle for existence among plants and animals 
is sharper and more exacting in the tropics than in cooler parts of the earth, 
birds form no exception. Moreover, so far at least as the region we are about to 
consider is concerned, the unfavorable or hostile elements in the environment 
of tropical birds differ greatly in kind or in proportion from those that must 
be provided against by birds of temperate climates. We should, therefore, 
expect to find a strongly marked difference between the habits, particularly the 
breeding habits, of the birds of the two regions; and this is actually the case. 
In British Honduras, where the observations were made on which the present 
remarks are based, those conditions which perhaps more than any other influ- 
ence the distribution and habits of northern birds, namely, food supply, ex- 
tremes of temperature, storms, etc., are factors scarcely to be taken into con- 
sideration. In speaking of the habits and distribution of bird's we are, of course, 
considering natural conditions only, leaving out of account changes wrought by 
the intervention of man. While the number of avian species in the above named 
region is large, the individuals are not abundant; on the other hand insects, 
fruit, etc., are extremely plentiful; the food supply, therefore, in most cases, is 
practically unlimited, while violent storms are unknown. The comparative scar- 
city of birds, in fact, in a land apparently so favorable for rapid increase, is at 
fii*st puzzling to the observer, but a closer study of conditions reveals an infinite 
multitude of enemies, whose ravages, especially during the nesting season, pre- 
clude the possibility of such an increase. It would be but a moderate estimate 
to say that through two seasons of observation by the writer one-half of the 
nests found while being built were robbed by natural enemies before the incuba- 
tion period was half over. 
These enemies may be divided into four classes: First, predatory birds, 
which comprise a comparatively large proportion of the avian fauna; second, 
reptiles, of which species and individuals are extremely numerous; third, small 
mammals, of perhaps a dozen species; fourth, insects, especially several species 
of ants. These four classes differ greatly in degree of importance, the reptiles — 
snakes and lizards — being probably the most destructive. 
As regards their structure and location, the nests of birds may be placed 
under four groups, as follows: First, open above and supported from beneath, 
on the ground, in grass- tufts, bushes or trees; second, in cavities of trees, rocks 
or banks; third, open above and pendant from a horizontal branch or leaf tip; 
fourth, roofed over, that is, entered by a hole at the side, either on the ground, 
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