You asked
Is the nikon af p dx 70 300mm f 4 5 6 3g ed vr long enough for birds?
Not really, at least not on its own for small birds. On APS-C this lens frames like 105-450mm on full frame. My wildlife and sport guide says birds want 600mm full-frame equivalent and beyond, so it will work for larger birds or ones that come close, but small birds will be tiny in the frame.
If you already have a Nikon DX body, the Nikon D500 and Nikon D7500 are the APS-C options I'd use with it, and cropping helps a little more. For serious bird reach, a 150-600mm or 200-600mm zoom is the better buy. Check buying used first, since long lenses hold their value but cost much less secondhand.
Written by Claude from this site's pages.