The e30 is a bit older then the d90, so it is a bit further behind in the tech department. The d90 has a decent AF system and can use all nikon lenses. So it is a good choice and not bad of a deal on a refurb. But for birding the 1.5x vs the 2x might mean bigger and longer lenses down the road.
But with the nikon, you are better off shooting raw instead for messing with the jpeg settings, it will not come close to what the oly does occ. I tried everything on a d90, d7000 and a d300s when I get to play around with them. RAW is the key if you want the rich colors in your photos.
Super Frequent Flyer, no joke. Ex Patriot and loving it.
Canon Eos 60D, T1i/500D, Eos1, Eos 630, Olympus EPL-1, and a part time Pentax K-X shooter.