Jazzgirl - 26A does work with waning as an anagram indicator, although, like you, I don't recall it being used for that purpose before. One of several questionable clues this week, I'm afraid.
I've not seen waning as an anagrind before. I guess the intention is "waning" = "in the process of changing" but that applies to the moon whatever phase it is in :/
I think it's tradition now the long primarily, and the challenge for the setter is to make the whole phrase relate to the answer. There's a lot of them about animals talking to each other so it makes sense, but it is contrived I agree.
20A was more of a challenge this morning, when half the clue was missing from the website! There was a misprint in 8D, too ... also now corrected. Perhaps the subs have been on the 22D?