IF memory serves, birmingham is a special airport (among 16 others) in the US that have special concerns mainly due to terrain.
invite others to double check...don't have my jepps with me
special airports require certain additional study/mainly due to terrain features like TVL etc.
Birmingham used to be on the 121.445 list but dropped off sometime in the early 2000s. The "additional study" tends to be look at a couple pictures of the airport taken on final and read a paragraph about what makes the airport special. Takes about 30 seconds. And it isn't required if the weather is good.