Comparative brain anatomy. Notice how our brains are much bigger than other animals', but have the same basic parts & layout. Mammal brains do vary a lot by species, though, so I'm curious what animal they used for their "typical" mammal brain.
Feeding adaptations in beaks. When identifying a mystery bird, the shape of the beak will tell you a lot about it’s lifestyle. Looking at the conformation of the body and the shape of the wings will also give a good indication as to what that bird has evolved to do (catch fish / bugs etc). Feeding adaptations in beaks