Ancient Roman priests raised sacred chickens that were used to interpret omens. For example, the chickens were used to predict the outcome of military battles.
Here’s how it worked: The chickens were let loose from their cages and had feed sprinkled in front of them. If they ate their food with gusto, stomping their feet, it was assumed that the gods were telling the naval leaders that it was ok to go to battle because the outcome would be favorable. If the chickens did not eat, the Romans assumed they were being told by the gods that they were destined to lose.
Of course, plenty of generals wanted to undertake battles with the permission of chickens, so one way they got around it was to deprive the chickens of food for a few days leading up to the decision. That way, the chickens would be hungry enough to eat regardless.
It was thought that no soldiers would willingly follow a general into war if the sacred chickens hadn’t given the right omen.
In 246 BCE, naval commander Publius Claudius Pulcher wanted to lead his fleet into battle with the Carthaginians during the First Punic War (264–241 BCE). However, his sacred chickens didn’t eat their grain. That’s when, according to legend, he made a fatal error in 249 BCE.
Seeming to mock the gods’ obvious omen, Claudius threw the chickens overboard into the sea, proclaiming that if perhaps they weren’t hungry, they were thirsty. A sacrilegious move like this would have likely horrified the troops.
Claudius and his fleet paid the price, suffering the only naval defeat of the entire war at the Battle of Drepanum. And it was a significant loss, with 93 of his 123 vessels destroyed.
Claudius was accused of treason and fined as a result. Variations of the story appear in the works of ancient writers Valerius Maximus, Suetonius, and Cicero. – WTF Fun Facts
Source: “Publius Claudius Pulcher, Roman commander,” — Encyclopedia Britannica