My cockatiels all settle on high perches at bedtime and sleepily chirp a little before actually going to sleep. My GCC does purr, but I have always felt this was a self soothing sound for him as he has no cage mate. Emmie CAG talks to himself before he sleeps, sometimes quietly rehearsing sounds he discovered during the day, sometimes trying out new words. The Senegal and Redbellied just perch and I hear nothing from them. If I disturb the flock by entering the room, the tiels and budgies panic call and fly around in defense. They quickly land and settle themselves and go back to sleep, especially if I leave the room promptly. No repeat of the sleepy sounds then.