2014托福考试阅读模拟试题训练16

　　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.

　　11. What is the main idea of the passage?

　　(A) Nesting material varies according to the

　　parrots' environment.

　　(B) Humidity is an important factor in

　　incubating parrots' eggs.

　　(C) Aviculturists have constructed the ideal

　　nest box for parrots.

　　(D) Wild parrots' nests provide information

　　useful for artificial incubation.