Symbolism, Imagery, Allegory
Do blue jays really hate Damien Hirst that much? Probably not. But the blue jay at the end of the novel, while Nick is wallowing in the misery of being dumped by Rachel, serves as a powerful symbol of perseverance.
"There's this blue jay that visits every morning without fail, and for about ten minutes it will keep flying into the glass wall and pecking at it" (3.16.1). Nick isn't sure whether the bird is sharpening its beak or trying to find a way into the house. It isn't until Colin suggests opening the glass walls that they discover the bird was trying to get to a colorful Damien Hirst painting the whole time.
Colin encourages Nick to "be the blue jay" for Rachel (3.16.52). Maybe it's because Nick hasn't been eating much, but he doesn't quite get it. Being the blue jay means keep tapping at the window until it opens: "take an impossible situation and make everything possible" (3.16.54).
In the end, it's Nick as the blue jay—literally flying around the world to get Rachel's mom and bringing her to Singapore—that gives Rachel the closure she needs. We wonder if Nick will keep being the blue jay for Rachel. We're not sure all the glass doors are open yet.