Great Horned Owl
Great Horned Owls are the most formidable of all North American Owls. They are nicknamed "tiger of the woods" because they are a fearless apex predator. Jack is not just a doctor, he's a trained soldier, vaillant in the face of Death. He carries those monsters still with him and every day combats them fearlessly.
The "horns" of the great horned owl, gives them sometimes a grumpy or silly expression, they do match Jack's dry, cynical exterior. Unimpressed and rarely very expressive when in the presence of strangers. He does rarely give a franc smile or even laughs. Those are truly just for private and intimate moments that only few can witness.
There is something nostalgic and comforting in hearing the hoots of an owl in the night. It's a steady low unmistakable sounds. Jack's voice is rarely high or elevated. No it's a low, calm, raspy voice that carries a weight. When things are spiraling, he is the anchor in the storm. Also the voice of the night shift.
Speaking of the night shift, if Robby is the Prince of the Day shift, Jack is the Guardian of the Night shift. Like the owl, he thrives when the rest of the world is asleep. The night is a shield for him, what you consider chaos is a controlled environment. He hides well , because the day is just too bright for many things and the dark allows for peace and respite from it all. It also equips him to guide those lost there , in the middle of the night for them to find their light back.
And like the owl, Jack is very perceptive, sees it all with a clinical eye. He's hyper-focused, no-nonsense and does not get distracted when focused on something. Though his hyper vigilance makes him sometimes too aware of everything and there are times he wishes to not see all these things.
Almost there I swear. In folklore owls are the symbol of wisdom, but are often lonely , that wise mentor with a heavy heart. Jack as a veteran has another view of life and death, he is an anchor to others, guides them, but is a creature of few words. He carries authority, but is guarded. Coach for many of his night residents.
Furthermore there is something haunting about Jack. He does sometimes seem to haunt the ER, appearing out of nowhere and vanishing when not needed. He's also silent when hurting too much , because his nature is not to harm, he just retreats and flies away. Now owls are one of the only birds who have a complete silent flight, you do not hear the flapping, their feathers are designed that way.
And last, from a more mystical point of view owls are a symbol fo the transition between life and death. Jack finds comfort in that edge between both, in that call of the void where he just feels so alive. And while he flirts with the abyss , he is bound by his word and his duty. Last symbol of the Owl. The Moon. Faithful and silent watcher of the night, always there, always a beacon , always a duty of silent and cooler comfort. That is who Jack is, for his people, he is just that presence that never goes away, that rock so unmovable.
But then one has to question , what happens when the owl's wings break ? What then ?