Crow's Nest is a location-based challenge in Captain Scarlett and Her Pirate's Booty. To perform this challenge in The Rustyards, it is required to reach the top of the scrapyard ship mast. It is worth 4 Badass Rank.
The mast is on the scrapyard ship in the middle of the map. Reaching the big cross-bar is sufficient to unlock the challenge. This requires an initial climb up the forward side, a jump across a gap in the corner to a ledge on the port side, and lastly a series of jumps from ledge to ledge at the rear.