Which Nikon DSLR is good for bird photography

The OP asked for an intermediate-level camera. I don't think the D300 qualifies as intermediate...

In any case, I think between a D300 with a mediocre lens and a D90/5200/even D3200 with a good lens, I'd pick the second any day

Btw, I use a D300 myself..

--
Check my blog for reviews, tips & tutorials:
Amateur Nikon
Follow me on Twitter:
@amateurnikon