I used to do this! Nowadays, I rarely have the creative energy to ponder it, especially given the wide variety of species I'm aware of and how variable each can be!

That said, sometimes a species will stick out to me. To write Campo Largo, for instance, I drew inspiration from real people I knew, and in a couple cases let my memories of people -- and their looks -- draw me to a specific creature or another. Notably, one character needed to be a lanky waterfowl, and when pelican didn't quite work, I went with heron instead.