By accident (usually)
People do sometimes prefer knights to ravens
“The first time I saw Riverrun, I was a squire green as summer grass,”
Jaime told his cousin. “Old Sumner Crakehall sent me to deliver a
message, one he swore could not be entrusted to a raven. Lord Hoster
kept me for a fortnight whilst mulling his reply, and sat me beside
his daughter Lysa at every meal.”
—A Feast for Crows
However, they seem more worried about mishap than malice
It certainly seems possible to shoot down ravens:
“Unless Lord Frey tells him,” Catelyn said sharply. “Theon, when you
return to my uncle, tell him he is to place his best bowmen around the
Twins, day and night, with orders to bring down any raven they see
leaving the battlements. I want no birds bringing word of my son’s
movements to Lord Tywin.”
—A Game of Thrones
And indeed, other people consider this a risk:
Catelyn knelt and took her father’s hand in hers. It was a big hand,
but fleshless now, the bones moving loosely under the skin, all the
strength gone from it. “You should have told me,” she said. “A rider,
“Riders are taken, questioned,” he answered. “Ravens are brought
—A Game of Thrones
As to when someone would shoot down a raven in the hopes of getting a message, the answer is presumably if they are suspicious. If a raven flies over a battlefield, it might be shot down on suspicion of coming from the enemy. If a raven leaves a castle and there are spies in a nearby village, it might be shot down. If someone sees a raven flying during an hour when they are not usually active, that could also be cause for suspicion. The raven population will not be depleted, because only during certain times and places will it be worth the trouble to target any ravens one sees.
It’s important to note that this is not always (or perhaps usually) intentional, though. It seems likely more people shoot down ravens for food than for information:
Ravens did not always win through. Some bowman could have brought the
bird down and roasted him for supper. The letter that would have set
her heart at ease might even now be lying by the ashes of some
campfire beside a pile of raven bones.
—A Storm of Swords
When Stannis spoke of the risks to his ravens, he counted storms and hawks among the dangers his ravens would face.
Stannis turned to Davos. “The maester tells me that we have one
hundred seventeen ravens on hand. I mean to use them all. One hundred
seventeen ravens will carry one hundred seventeen copies of my letter
to every corner of the realm, from the Arbor to the Wall. Perhaps a
hundred will win through against storm and hawk and arrow.
—A Clash of Kings
And, as we see from the previous passage, ravens are frequently brought down merely out of hunger.
It seems there are two reasons not to entrust a sensitive message to a raven:
- Sensitive messages are usually important. If 14% of ravens fall victim to misadventure, then the message is lost quite frequently. A knight may be killed, but perhaps not nearly so often.
- Accidental interception would be the main worry. If some hunter shoots down a raven for a meal, they are bound to notice the message. And if they can read (or know someone who can) and have loose lips, the message could travel to the ears of those who could use it for harm.