APS-C can be a real advantage for wildlife, but not because the lens actually becomes longer. The sensor simply captures a smaller portion of the image circle, giving a narrower field of view—similar to cropping a full-frame image.

Where APS-C helps is resolution on the subject: if the APS-C body and full-frame body have the same megapixel count, the APS-C frame keeps all those pixels on the cropped area, while a full-frame image cropped to match will have fewer pixels left. That can matter for printing or heavy cropping. For web-sized output, the difference may matter less.

So APS-C is often attractive for wildlife because it can give you more effective subject detail without needing a longer, more expensive lens.

Two caveats:

• If a full-frame camera has similar pixel density, the advantage shrinks.
• Don’t think of crop factor as making a 200mm f/2.8 into a 300mm f/2.8. The field of view is like a longer lens, but for equivalent framing and depth of field/exposure comparisons, aperture equivalence changes too.

Bottom line: APS-C is often a practical wildlife choice for extra framing flexibility and pixel density, but it’s not magic magnification.