One summer evening I was sitting by the open window, reading a good science storybook. (79)I was so interested in the story I was reading that I did not notice that it was getting dark. When I realized it was too dark for me to read easily, I put the book down and got up to turn on the light. Just then I heard someone crying, 'Help! Help!' it seemed to come from the trees at the other end of the yard. (80)I looked out but it was now too dark to see anything clearly. Almost immediately I heard the cry again. It sounded like a child, but I could not imagine what anybody could be doing in our backyard, unless one of the neighborhood children had climbed a tree and had not been able to get down. I decided that I should go out and have a look in the yard, just in case someone was in trouble. I turned on the light and found for myself a flashlight and a baseball bat in the room. I thought they might be useful. Armed with these, I went out into the yard. Once again I heard the cry and this time there was no doubt that it came from the trees at the far end of the yard. 'Who's there?' I called out as I walked across the yard towards the trees. But there was no answer. With the help of my flashlight, I searched all over that end of the yard, including the branches of the tree. There was no sign of anybody or anything. I came to the conclusion that my imagination was playing tricks on me, probably because of the story I was reading about strange creatures on another planet. Feeling rather foolish about hunting around in my own backyard with a baseball bat, I went back into the house and put the bat and the flashlight away. I had just sat down to read my book again when I was frightened by the cry of 'Help! Help!' from right behind me. I dropped my book and jumped up. There, sitting on the table was a large green and red bird. It was my neighbor's parrot(鹦鹉)!While I was out in the yard, the parrot must have seen the light in the living room and come in through the open window. One summer evening the author was reading by the open window because ______.