Hey these are all pretty good - my two cents on each one:
#1's kinda been covered - the composition is great, just needed a little cropping and a lot of contrast. Great shot!
#2 is one I really like too - there are parts that are blown out (overexposed) but it just works in this shot and actually serves to really highlight the leaf. It doesn't distract me at all.
#3 I think is my least favorite of the bunch, and there are a couple things I can point out. First, try to make sure your horizon is level - in this shot it's slanted just a tiny bit to the left. Also, since the sun was behind your subject, your subject turned out pretty dark. Typically I'd say, "fill flash" but let's be honest, this was a nature shot and a shot of opportunity and I doubt the bird would have stood there and watched while you set up a softbox. The focus actually looks just a touch soft to me as well.
#4 I can't help but think that it would look better as a portrait crop, with the branch on the right side of the frame cropped out entirely.
#5 I love it, but this time I am going to complain about the blown highlights. Dropping the exposure down by a stop or so would have retained more detail in the mushrooms and given a bit more shadow depth to the grass, in my opinion.
Nice work and I look forward to seeing more!