You asked

Is the canon rf 100 500mm f 4 5 7 1l is usm long enough for birds?

It's a little short for most birds on full frame. At 500mm, it falls under the 600mm equivalent my wildlife and sport guide suggests for birds. On APS-C, though, it frames like 160-800mm, which is plenty for most garden and lake birds.

Good pairings from the catalogue:

The lens gets darker at the long end (f/7.1), so bright days suit it best. Long lenses also hold their value, so buying used can save a lot.

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