"to owe" is used when the verb "devoir" is followed by a noun, when it is followed by a verb, it means "to have to, must".
More about this verb:
I once read about a journalist whose grandfather had a reputation in the family for being a master linguist because of his ability to speak a dozen languages which enabled them to survive forced migration. The journalist was surprised to discover late in life that all his grandfather actually knew were currency denominations and different language variations of the phrase how much is a chicken here?
Apparently the answer provided him with all he really needed to know about the local economy wherever they were forced to travel
The French phrase did not specify who was owed. It could be the Chicken God. Consider in English:
"I owe fifty dollars"
It does not say who is owed the money, but it is only one phrase in a conversation. More information is needed, but it is perfectly valid.
"Je dois 50 euros"
That is basically the phrase with the chicken, but the currency is different.
Remember jinxing people? Making them owe you cokes? Things other than money can be owed. People can even owe respect or time.
It means that some circumstance has come about (barter economy, private arrangement, wager) where someone owes someone a chicken.
In barter economies, chickens are like the currency equivalent of a ten dollar bill as compared to cows which are like thousand dollar bills. Chicken/ten dollar bills are much more suitable for regular transactions than cow/thousand dollar bills.
People who spend all their lives in large cities in advanced economies can rest assured they will never hear or need to use this phrase. For much of the world's population, including urban populations who look slightly outside their own personal experience, this phrase has some interest.