I'm drawing an image that is supposed to be a visual representation of the song The Crow, the Owl, and the Dove for my digital art final.
Naturally, I drew an image of a crow, owl, and dove sitting on a tree branch together. Here is a sketch of what I have done so far.

I used photograph references for the bird sketches, since I know almost nothing about drawing birds. Please ignore the awful moon in the top-left, I don't care about it yet. I'm going to do something special for it later on. I'd like some tips on how to do lineart, though. I'm using photoshop, but I want to know what tools other digital artists use to make their lineart look so crisp.
Also any other general art tips would be great. I don't mind criticism but please understand that I'm pretty novice.
There is no magical tool to make your lineart smooth. You need to use long, broad, smooth, precise strokes to produce good lineart. Photoshop is a good choice program-wise but a program is just a tool, and if you're not going to use the advanced painting features photoshop has I'd go with PaintTool SAI instead, it's a bit more streamlined/efficient/user friendly imo
Also, do not start with the lineart, you should be roughing everything out on a separate layer and once you have that looking how you want it, you trace overtop of it with the technique I mentioned earlier
Alternately keep doing the scribble-thing and just go over the lines over and over again with the pen and eraser until it looks right, but I don't recommend it as it takes forever and it's generally a bad habit that should be avoided
You should probably look up a few references for trees too and think about your composition values, if this is an art final you should take a lot of care in the planning, almost as much as the execution itself, I'm not sure what you're going for stylistically nor do I know the project requirements or the level of the class you're taking, but from what I can tell you want at least semi-realism