A Day's Shooting

My uncle is a keen sportsman. He often goes shooting during the week-end and usually comes home with a bag full of birds. Last Sunday evening he came home earlier than usual.
He didn’t say anything when he came in. he threw his bag on the table and sat by the fire.
He looked tired and cross.
“Didn’t you have a good day, dear?” his wife asked.
“What do you think?” he answered crossly and pointed at the bag.
“Look at this bag! There is only one bird in it and it cost me a lot of money!”
“Weren’t there any birds?” my aunt asked kindly.
“Hundreds of them!” my uncle said, “but I spent the day arguing with a farmer.”
“What happened, dear?” she asked.
“I shot my first bird at five o’clock this morning. Soon afterwards I aimed at another one and fired. But I don’t know what happened. I think I slipped because I didn’t shoot the bird. I hit a cow and killed it. The farmer who owned it got very annoyed with me. I argued with him for hours and in the end I had to pay him £50!”
“Oooh my god, what is a terrible!” my aunt startled.