Some great pics! Keep at it.

If you want to control what your pics look like, if your camera supports it, shoot in RAW or RAW+JPEG.

The three components to learn about and practice with are ISO, Aperture, and Shutter Speed.

And aperture really is the most important one to master if you can master only one. By controlling aperture you're controlling how much light passes through the camera lens. We measure aperture in "f-stops". F-numbers you may see referenced might be f/1.4, f/2.8, f/5.6 etc. The larger the hole the more light comes in. The smaller the hole then less light. A f-stop of f/1.4 allows the most amount of light in compared to a f-stop of f/5.6 which allows less light in as it is a smaller hole. So initially confusing, small f-number equals a lot of light shooting wide open, and a large f-number equals less light.

A larger f-number such as f/18 means almost everything in both foreground and in background will be in focus. A smaller f-number such as f/2.8 means pretty much what you center on as your focal point will be in focus and everything else will be soft or out of focus.

So aperture is uber important because it has a large impact on depth of field (DOF). Do you want the bird and the feeder and the fence in the background to all be in focus, or do you want only the bird to be in focus and everything else blurry?

Hope this helps. Best to do is get in manual mode on your camera and change your f-stops greatly shooting the same picture from same position in same light. Then review those pics later and see how the depth of field and focus has changed.