Clyde has been very quiet -- for him -- the last few days. It's been hot and the dogs (and us!) aren't as active, either, but I'm still new at having a Quaker and I got to worrying.
Mind you, he certainly seems to feel fine. He eats and drinks and is always ready to pop out and ride around on a shoulder and chew on my ear and all of that, just as usual. But in between times, he's not making as much noise as usual. Even sitting on my shoulder, he seems to be quite content to just sit there if I'm surfing the Net or reading, but if I say something to him, he immediately responds, and I sometimes catch him out of the corner of my eye watching me with his little head cocked, waiting for me to say something. He has a bathtub in his cage to get wet in if he's too hot, and I'm on vacation so he gets out several times a day for lots of attention. Am I worried for nothing? And of course, while I was typing this, he chirped several times.
He may just be calm and content.
I bought him a recording of classical music yesterday because it had Beethoven's Fifth Symphony on it and I've been teaching him to whistle that and playing it on my flute for him, and since I put that on, he's been whistling and singing like crazy. He's not necessarily whistling the same notes the symphony's playing 
, but he's clearly singing along. And sometimes he does sing the same notes they're playing, or at least he's in tune and singing counterpoint. It's so cute.