Welcome to Nikonians! You are confusing Nikon with Canon.
All Nikon DSLR's support AI, AI modified, and AIS MF lenses including the ability to focus to infinity without an adaptor.
To use a Canon MF (FD) lens on a Canon DSLR you will need an adaptor with a lens element to support focus to infinity.
I can confirm that AI modified, AI, and AIS MF lenses focus to infinity on Nikon entry level DSLR's as well as the Pro bodies. Keep in mind that the entry level DSLR's do not support metering when used with MF lenses without CPU's. You will be limited to Manual exposure mode, Manual ISO, and Manual or Non-TTL Auto flash modes. The D_ series, D_00 series, and D7000 support metering with AI, AI modified, and AIS type MF lenses without CPU's. Good Luck and Enjoy your Nikons!