This morning, I let my parrotlets out but was waiting until my coffee finished brewing before liberating the tiels. (They have a habit of flying into the kitchen). However, after the coffee was done, I got sidetracked and forgot to let them out.
My two parrotlets immediately started yelling at me, and flying back and forth to the tiel's door. They had never done that before. They were reminding me in no uncertain terms to "Let them out!"
On a daily basis, in so many ways my flock reminds me to never underestimate the intelligence of birds.