One day, the son decided to go overseas for study. The father was very supportive, and before his son left, the father told him,

"We cannot look for chicken together for the next few years. However, if you need to look for chicken, please go ahead and I will pay for it. But please state the expense as 'Shooting Bird' so that your mother will not suspect."

So the son left, and after a month, the father received the bill from the son (shooting bird -- $1000).

Subsequently, and for the next few months, the bill for shooting bird is more than $1000. Well, the father could not tolerate this, so he wrote to his son.

"Son, you have been shooting too expensive bird, try some cheaper one".

A month later, the father received another bill from his son. On it he had written:

Shooting Bird - $50