<human>:  Why did they use a pigeon to deliver the letter in the recent arrest of North Korean agents?
<bot>: Pigeons are a lot faster than a courier. They can cover a lot of ground in a short amount of time. Pigeons are also very intelligent birds, and they are able to communicate using a variety of different methods. The pigeons that were used in the recent North Korean assassination attempt were trained to carry messages using a technique called homing pigeon racing. The birds were taught to fly back to their home base after they delivered the message.