It looks pretty dark. What do the other photos look like? Why 1/800s?
And why ISO 100?
It's quite underexposed, plus it looks like maybe the sun was out in front of the bird, so you got the front of it in a harsh light, and the rest in complete shadow.
Birds are not nearly as easy to shoot as people THINK they are going to be. Generally, trying to get good bird photos serves to make you appreciate people who can get good bird photos more!
Ideally, try to shoot with the light behind you, so you are basically between the light source and the bird. Focus on the eye. And watch your composition; try not to have your subject smack in the middle of the frame like it is here. Additionally, this would be a more effective image if the bird were facing you instead of facing away. No, you can't really "control" that per se--you can't just tell the bird to turn around (well, you CAN, but trust me, there's really no point, lol). But you CAN learn when to actuate the shutter and when to wait for a better shot.
There's a lot more to it than that, but those are some starter tips based on the issues with your image.
In general, for a perched bird, I'd shoot at about 1/500, and start with an ISO of 400 and go up if necessary.
For birds in flight, generally you need an absolute minimum of 1/1000 sec., so your ISO is often going to have to go higher (sometimes much higher) as well. You might also get away with a wider aperture, depending on your lens.
What are you shooting with, camera and lens?
EDIT: Never mind about which camera and lens, robbins and the OP posted while I was composing my masterpiece.
