Birds are typically smaller and harder to approach than other wild animals, so you often need a longer focal length to photograph them. While you can take frame-filling shots of a large mammal with a 300mm or 400mm lens, you may need to use a 500mm, 600mm or even 800mm lens for some types of bird photography.
The size of your camera's sensor can help, though. The APS-C sensors inside EOS M mirrorless cameras and APS-C EOS DSLRs are smaller than full-frame sensors, so in effect they crop the image from the lens, making the subject fill a larger proportion of your frame. The "crop factor" is 1.6x, meaning that if you take an EF lens designed for a full-frame camera and use it on a camera with an APS-C sensor, you will in effect increase the reach of the lens by a factor of 1.6. For example, a 400mm EF lens on a Canon EOS 250D
gives a view equivalent to a 640mm lens (400 x 1.6) on a full-frame camera. Other characteristics of the lens stay the same, but larger sensors do tend to be capable of narrower depth of field, which produces more background blur.