Rawr. So much interest! This birdy is happeh. I got back from vacation earlier this week so haven't gotten to work on much, but I plan to do some animal sketches this afternoon, lessee then!
As for tutorials, to be honest- I don't think I'm really that good! I wasn't really schooled in art beyond your basic art classes, and had to learn everything online. DeviantArt has been a fantastic place for tutorials and really helped me grow as an artist. I'll see if I can find the tutorials I specifically used a lot, see if it helps anyone else :>
I'll also say that having reference images is definitely key to improving yourself. Asides from things I've spent years doodling, like dragons which I can make up within 3-4 minutes of sketching, I use a lot of references to help me identify how anatomy is supposed to be versus what I end up drawing myself.
I started working on an arctic fox for a friend a few days ago. I'm pretty decent with canines, but I still struggle with anatomy, so I open up a reference picture beside my empty page, and start scratching up a rough outline:
I wanted to learn the fur direction, and specifically how the back of the legs look in that sort of pose, so I scribbled around a bit to learn what personally feels comfortable to me. The end result is going to be quite different from the reference picture, if only because I tend to stylize my art the moment I have a solid feel for the character I'm making. It's just how I learn personally. Never be afraid to use references as you art it up. It'll only help you work through your weaknesses as you go on to produce more art and learn to develop your own style.