It’s a common tendency to shoot in Auto mode as a novice bird photographer. But, you’ll have no control over the resulting exposure. Instead, start using the semi-automatic modes.
They are extremely simple to use and will give you incredible results. Start with the Aperture Priority (Av/A) mode. Most of the pros use this mode, including me. It allows you to choose the aperture (which will define the resulting depth of field), while the camera chooses the shutter speed for you. Combined with the Auto ISO setting (discussed next), it’ll ease your tension of worrying about the right settings
If you are unable to get the required shutter speed, in the case of low light, choose Shutter Priority (Tv/S) mode. It allows you to select the shutter speed (which helps you to either freeze the action or blur it), while the camera chooses the aperture for you. Combined it with the Auto ISO setting (discussed next) for ease of use.