Pixel density for bird photography

[Tannin]

In another thread, which I didn't want to drag off-topic .....

Tony wrote:
the D3 & D700 don't have enough reach for bird work

Please explain!!

For bird photography, you need pixel density. Simple as that. The D3 and D700 are very fine cameras, but they have the lowest pixel density of any SLRs sold today, and are generally avoided by people primarily doing bird work. Nearly all bird photographers use cameras that have high-density sensors.