This puzzle was for the birds.
Besides the 5 theme answers, we also had EMUS (15A: Cousins of ostriches). Actually, it's not a bad puzzle for a Monday. I don't really know OLDBUZZARD (24A: Cantankerous fellow) as a phrase I'd use in conversation, but the other four are solid. On the plus side, you have the nice pairing of AMENABLE and QUATRAIN, mirrored in the other corner by SHOUTOUT and PANDEMIC. The NW and SE are likewise nicely chunky, with SEDERS an unfortunate unnecessary plural.
But the middle has some stuff I don't like. What's with 21D: Like many Mexicans' forebears (AZTECANS)? Wouldn't they just be Aztecs? I'm also not fond of 34D: Not touched, as a boxer (UNHIT). Can we just put "un" in front of words and make an acceptable entry? The two partials USEIT and IREST are at least unusual (the former clued nicely with a spelling bee reference).
Things I do like: 25D: One trying to grab a bite at the theater? (DRACULA), 59A: N.Y.C. home of Magrittes and Matisses (MOMA, because it's a great museum, if expensive. Helps to have a mother with a Met ID), and 49D: Like 18 1/2 minutes of the Watergate tapes (ERASED).
Well, they can't all be gems like last Friday and Saturday.