WEAPONS EXPERT 3: Kill three birds of prey using only a Tomahawk.
You will need to complete “Paying a Social Call” (Chapter 2) as a prerequisite, and its reward is “Weapons Expert Gun Belt available at any Trapper”.
This guide will tell you how you can complete this challenge in Read Dead Redemption 2.
You have to kill a big or medium-sized animal, move away from the carcass and wait for crows or other birds of prey to spawn and fly down.
You can use the Dead Eye to mark the bird and throw the Tomahawk.
If there are no mete birds to kill, you will need to move away from the area a little and get back soon after.
Another easy way to complete the challenge is by killing the Vulture and the Eagle that spawn on the railing of Bard’s Crossing Bridge.
After killing them, you have to save and reload to make the two birds appear again on the railing.