"Sarji kept carrier-pigeons"

A carrier pigeon
Public DomainA carrier pigeon - Credit: Patrick Edwin Moran
Carrier pigeons are homing pigeons that can be used to carry messages.  Homing pigeons are able to find their way home even from a very long distance away.  If a message is written on lightweight paper and rolled into a small tube, it can be attached to the pigeon's leg.  The bird will then carry the message back to its home.

Carrier pigeons have been used throughout history and played a vital role in delivering important intelligence during World War I and World War II.

The story of Cher Ami the Carrier Pigeon (from Home of Heroes)