To foul one’s own nest

On my writing blog I have been writing about idioms. Some of these relate to birds. Here is another of these interesting expressions.

“To foul one’s own nest.”

Origins:

This expression probably comes from the fact that many birds are careful not to foul their own nests. The droppings of the young are picked up from the nest by the adult birds and dropped on to the ground below the nest. There has been a proverb in existence for over a thousand years which says, “It is a foul bird that defiles its own nest.”

Meaning:

This idiom means simply to harm one’s own interests.

Example:

“By not picking up things after their teenage son, they allowed him to foul his own nest.”