12 FOREWORD 
seclusion for laying and nesting — from maternal fear for 
the safety of the young. 
The sexual instinct in indoor caged birds in a zoologi- 
cal garden is dormant. Very few copulate and very few 
lay eggs; pigeons and Mexican conures {Conurus holo- 
cMorus) are exceptions to this general rule. 
Probably because the sexual instinct is dormant the 
males never fight over the females among perching birds, 
and very rarely kill each other. In some species of 
finches, however, as the chestnut-eared {gn. Amadina), 
the females fight among themselves if there are not 
enough males. 
Ovoviviparous reptiles breed more often in captivity 
than one would expect ; and egg-laying snakes often lay 
eggs, which of course are only hatched artificially. 
Birds suffer less than mammals from the psychologi- 
cal effect of captivity. The mental development of a bird 
is much lower. With few exceptions, like the ruffed 
grouse, the bird accepts captivity easily and becomes 
tame, though he ^dll not stand being touched. He views 
his keeper and visitors with indifference or friendliness. 
If a bird house is bright, cheerful and sunny, all the 
inmates thrive and appear to be happy. These conditions 
undoubtedly affect the health of the bird, as is evidenced 
by their plumage; bright colors that are lost in a dark 
and gloomy house are retained and developed when the 
house is cheerful and sunny. There are some birds, how- 
ever, that never retain their colors in the captivity of a 
zoological garden. Among them are the scarlet ibis, the 
American flamingo, and the roseate spoonbill. It has 
been suggested that the loss of color is due to the lack of 
something in the diet, mineral or organic, that the bird 
gets in its natural habitat. Tame scarlet ibises living 
with the chickens about the dwellings of natives in 
Venezuela retain their brilliant color. The material of 
the beautiful red color on the under surface of 
the wings of the touracou contains copper, yet these 
