How our food offered to the crows and Brahmanas reach the deceased ancestors?

We offer food to the crows and brahmanas on Amavasya and/ or Shrardha (annual thithi).

The crows and brahmanas eat and get satisfied.

Ok, How will it satisfy the deceased ancestors who are in the Pitru Loka or other worlds?

Kanchi Sankaracharya Sri Chandrasekarendra Swami explains nicely:

"When we send a money order to a person from India to the USA, our money does not reach the USA, but, the equivalent of dollars are given to the recipient in the USA. 

Similarly, when we offer food to the Crows and Brahmanas, the eater may be a man or bird. But, if the deceased person had taken birth as a cow or bull, the food eaten by the brahmanas or crows here is converted as Grass and given to the cow/ bull.

Thus, the offered food reach the ancestors in a particular form that can be consumed by the ancestors in their respective worlds."

Thus, if we do not offer food to crows and brahmanas, our ancestors may starve in their current world.

That is why, we should offer food to as many people as possible - particularly to brahmanas and crows - both of them are considered as the representatives of our ancestors.