The Great Egret

I spent some time yesterday watching a Great Egret near the lawn of my building. There it was, purposefully strolling left and right, feeding, enjoying the day. How come birds don't ever act depressed? As far as I can tell, all complex organisms with a certain mental capacity should be able to experience chemical imbalances at a certain point in their life. Perhaps I caught it at a time when its imbalance had just passed, or maybe before an upcoming episode.
The Egret ignored my thoughts and kept moving. No time to rest for the hungry bird - I guessed.
"There - there is something moving in the grass, and it's mine to take," the Egret thought, “it’s mine to take and I'll take it." And so it kept moving, left and right, strangely tilting it body back and forth reminding me a lot of an imbalanced teapot resting over a small grape.
"What's your purpose in life?" I asked the Egret.
"I must eat," it answered darting quickly over to its right to catch a grasshopper.
And that's that. I had my answer. This life's purpose was to sustain itself. The complex neurons in the brain, the extensive neuron network of memories, thoughts, and desires had developed to sustain the structure of the overall organism. Life exists to exist. Life's purpose is to the sustain itself, to assure its survival.
The Egret tilted its tiny head and nodded at me, "Why are you just sitting there staring at me?" Its little yellow beak trembled strangely and I thought the bird smiled. "Come-on join me, there's plenty of food out here."
"No, my little friend," I said and winked at it, "I must create a meaning for myself. You see, I'm not hungry now and so I think."
"But why not rest when you're not hungry? After I eat, I usually lie underneath the green bush, right over there," the Egret pointed to a small fichus bush a few yards away.
"I must move," I answered, "there is time for rest at night when I lie on a bed and close my eyes. But not now. During the day I must move and think and live."
"I live when I'm resting," the Egret eyed me with suspicion.
"Ah, yes indeed, but see, I have my food ready and waiting for me when I'm hungry so I don't need to look for it. Instead, I can sit where I'm sitting now and reminisce about the meaning of all this."
"You must be depressed," the Egret shook its beak again and proceeded to ignore me for the rest of the afternoon.