Shooting Birds

There was a father who was very close to his son. They used to go everywhere
together including picking up women, which they referred to as "calling
chickens". One day, the son decided to go overseas for study.
The father was very supportive. Before his son left, the father told the
son, " We cannot call chicken" together for the next few years. However, if
you need to call chicken, please go ahead and I will pay for it. But please
state the expense as 'Shooting Birds' so that your mom will not suspect."
So the son left. For the first month, the father received the bill from the
son (shooting bird - $1000). Subsequently for the next few months, the bill
for shooting bird is above $1000. The father could not tolerate any more, so
he wrote to his son. "Son, you have been shooting too expensive bird, try
some cheaper ones"
A month later, the father received another bill from his son. It wrote:
"Shooting Bird - $50, Rifle Repair - $2,000"