Birds can be pretty tough to do, but if you'll stick with it, you'll improve pretty quickly. You'll also become obsessed with it, if you're like me, but that's another story...
In the first photo, there's just TOO many distracting foreground branches covering up the bird. There's nothing you can "do" about those, other than just wait until a better opportunity presents itself.
The other two are much better compositionally, but they are pretty underexposed--what were your settings? (I could probably check the EXIF data, but I haven't finished my morning coffee yet, so motivation is nonexistent).
I do think they could both use some cropping, as the bird kind of gets lost in the frame. I like the framing made by branches around the sparrow; I wonder how it would look if you cropped one of them to a portrait orientation with just that branch "frame" around the bird?
Some things that have helped me improve bird photos:
--Place some feeders close to bushes or natural places where the birds can land. They will be attracted to the feeder and will land on the surrounding branches, so you can still get photos of them in "natural places." I put seed up on top of a small woodpile in addition to my feeders.
--Set yourself up somewhere where you have a clear line of sight to the birds then make a "blind" of sorts. For example, if you shoot out an open window, put some material over the window with just a hole for the camera lens to "conceal" yourself from the birds. My backyard setup is I have a big pile of branches, etc from a tree that fell. I set up behind that pile (wearing camo hunting clothes or something else dark and inconspicuous) and then wait. It's pretty close to the bushes and tree branch near the wood pile so I get pretty decent shots that way.
Another way I've gotten some pretty close shots: Sit in your car. Backyard-type birds are used to vehicles for the most part, so they pay them little attention--therefore, they make pretty decent "blinds." I pull mine up about six to eight feet from the woodpile, roll down the window, and wait. As long as I don't make any sudden moves, most of the birds pretty much ignore me. My tufted titmice and chickadees seem to be the most skittish. The sparrows will just sit and stare at you.