Wow! Thank you for that website, that is so awesome! I've looked a little bit into the different calls but I didn't know there were so many! And he doesn't seem to be stressed out, he's been living with them since he recovered and was all cleared and just recently started making those calls. I keep a close eye on him since he is the smallest. I think it could possibly be the release call too but I have heard him do the trill as well. So cool!