Questions 11-22
Avicolturists, people who raise birds for commercial sale, have not yet learned
how to simulate the natural incubation of parrot eggs in the wild. They continue
to look for better ways to increase egg production and to improve chick survival rates.
line When parrots incubate their eggs in the wild, the temperature and humidity of the
(5) nest are controlled naturally. Heat is transferred from the bird's skin to the top portion
of the eggshell, leaving the sides and bottom of the egg at a cooler temperature. This
temperature gradient may be vital to successful hatching. Nest construction can
contribute to this temperature gradient Nests of loosely arranged sticks, rocks, or dirt
are cooler in temperature at the bottom where the egg contacts the nesting material.
(10) Such nests also act as humidity regulators by allowing rain to drain into the bottom
sections of the nest so that the eggs are not in direct contact with the water. As the
water that collects in the bottom of the nest evaporates, the water vapor rises and is
heated by the incubating bird, which adds significant humidity to the incubation
environment
(15) In artificial incubation programs, aviculturists remove eggs from the nests of parrots
and incubate them under laboratory conditions. Most commercial incubators heat the
eggs fairly evenly from top to bottom, thus ignoring the bird's method of natural
incubation, and perhaps reducing the viability and survivability of the hatching chicks.
When incubators are not used, aviculturists sometimes suspend wooden boxes outdoors
(20) to use as nests in which to place eggs. In areas where weather can become cold after
eggs are laid, it is very important to maintain a deep foundation of nesting material to
act as insulator against the cold bottom of the box. If eggs rest against the wooden
bottom in extremely cold weather conditions, they can become chilled to a point where
the embryo can no longer survive. Similarly, these boxes should be protected from
(25) direct sunlight to avoid high temperatures that are also fatal to the growing embryo.
Nesting material should be added in sufficient amounts to avoid both extreme
temperature situations mentioned above and assure that the eggs have a soft, secure
place to rest.
【題組】12. The word "They" in line 2 refers to
(A) aviculturists
(B)birds
(C)eggs
(D) rates
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