Beginner's question: opinion on cropping

No, only amateurs are commonly cropping.

Then you have made errors before - knowledge and perseverance does get you very far, especially when birding. If your focal length doesn't suffice then you need to think your way around this constraint - compositional cropping isn't a solution, it's a problem all by itself because it puts you into a wrong mindset...

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regards
Karl Günter Wünsch