Crap, I just wrote out a book for you but I went to find a link and accidentally used the same tab and lost it all.

I'll try to summarize.
You're doing a good job keep your subject in the right part of the frame and you even used some natural framing in #4.
I think the problems with these pics is that they are flat, you've lost detail in the branches, and you have counter-productive intersecting lines.
#1 is close to being a photograph, but there is almost no detail. It's underexposed. It's a tough shot because the sky is backlighting it. The other problem is that there are very strong intersecting lines attracting attention away from the subject. It does have some depth and the subject (the leaf) is the most prominant of the pictures.
#2 is a "snapshot" for several reasons. There is no foreground or background, no details, the unidentifiable subject (the nest?) is too small to be interesting or...well, identifiable, and there is too much going on in the focal range. It's probably a limitation of your lens to get a shot of this particular subject.
#3 might be an interesting subject, but you chose to shoot it in a very uninteresting way, straight on. This makes it look more like a pattern for clothing than a photograph. Try that one again, but from different angles...up, down, left, right...closer, further away. Use the lines to your advantage, not to your disadvantage. I'm not sure if we can post links here, so just google "digital photography school composition" and check out the first non-ad link.
#4 is the same as #2, only more so.
I hope this gives you some ideas.