During World War I, pigeons were used for communication between soldiers and commanders because radios were too heavy, expensive, and messages could be intercepted by enemies. Soldiers would attach brief messages to pigeons' legs explaining their needs, then release the pigeons to fly back to headquarters. Over 100,000 pigeons served the British, American, French, and German armies during WWI, alerting headquarters when they returned so help could be sent.

1.
Pigeons in WWI
In the First World War soldiers that fought on the front line needed to be able to communicate with other soldiers
and their commanders. For example, they sometimes needed to call for help when big dramas occurred, or ask for
extra supplies, as well as telling them how things were going.
In those days radios were heavy to carry around, expensive and unreliable. The enemy could also intercept the
messages. They did use telephones and telegraphs but they had to use wires which were easily broken. Back then,
things like mobile phones, satellite phones and walkie talkies weren’t invented.
Pigeons were a good choice for communicating because they could fly a long way and were pretty fast. The pigeons
had a coop near the headquarters and then the soldiers took them in a little cage to where they were fighting. When
the pigeons were needed, the soldiers took one out, wrote a brief message explaining that they needed help, put it in a
little canister on the pigeon’s leg and threw the pigeon into the air to fly back to the headquarters.
Sometimes the pigeons were shot down which meant that the troops had to send out another
one. When the pigeon got back to its coop, a little bell rang to alert the keeper who got the
message. Then the headquarters could do something about the message. Sometimes pigeons also
carried cameras hanging around their necks to take pictures of the enemy’s position.
Pigeons were so important that about 100,000 were used during WWI. They were used by the
British, American, French and German armies. Australia used pigeons too but not until World War Two
(http://www.anzacday.org.au/history/ww2/anecdotes/pigeons.html).
More information: http://www.edinburghs-war.ed.ac.uk/system/files/PDF_birds_messengers.pdf http://www.historylearningsite.co.uk/pigeons_and_world_war_one.htm
http://www.telegraph.co.uk/history/world-war-one/10566025/Honoured-the-WW1-pigeons-who-earned-their-wings.html