Can I use an extension with this lens for birds please?

[Loupey]

Also, when shooting birds quite close, I sometimes back off on the zoom to be able to spot them easier. Once I have them in my sights, I quickly zoom in.

That's what 100mm, 200mm, 300mm, 400mm, 500mm, and 600mm primes are for. Just have to change lenses real fast

[mn shutterbug]

Good one, Loupey. That one cracked me up.