Oh boy, you just opened the floodgates ( u/biscosdaddy u/fisharefriends23 feel free to add to this list)!
For birds, there is Avian Osteology by Gilbert, Miles and Savage, and Osteology for the Archaeologist vol 4 & 5 by Stan Olsen. These are my favorite go-to books for birds. Avian Osteology is quite pricey, but the other is reasonably affordable (and a bit better in my opinion). This book by Cohen and Serjeantson is also handy, and is a pdf.
For mammals, Stan Olsen has another volume that covers mammals (same link as above). Gilbert also has a Mammalian Osteology book, but again can be a bit pricey. Comparative Osteology is also good for some of the more common animals and is reasonably priced. There's a lot more out there for mammals, this is more of a "starter pack".
Yes definitely a bird scapula. I'm heading back to my lab for a minutes and I'll look at a couple of bird bone books and see if it has robin in there as a comparative.
For those interested, Gilbert et al. Avian Osteology has lots of good illustrations: https://www.amazon.com/Avian-Osteology-B-M-Gilbert/dp/0943414830
Also, Lee Post's Bird Building Book (and the other volumes for that matter) is amazing: https://www.theboneman.com/store/p39/birdskeletons.html