Pigeon Post Wiki

Pigeon Post, or commonly known as carrier pigeons, was first known to be used by Noah.  It goes back over 3,000 years of history to deliver messages using a domestic breed of pigeons.  They were very useful throughout history, especially World War I, World War II, and the Vietnam War.  They are still in use today by the U.S. to spot shipwrecks from helicopters, they are raced in France, and used as drug carriers by traffickers to carry ten grams of heroine between Pakistan and Afghanistan to escape detection.  

http://www.nytimes.com/2004/01/30/style/30iht-blume_ed3__1.html