Ilene,

I have used a minidisc for several years and I'm very happy with it. I can
record from tapes, CD's and computer files directly onto the minidisc. With
MP3 you would have to figure out how to "rip" from tape or CD's to MP3
format, a process that does require the right kind of sound card on your
computer. Minidisc would also allow for recording in the field, which you
can't do with MP3.
In terms of models, I picked the Sharp MD-MT821, as it:
Is made of metal, not plastic and may stand field use a bit better
Has an internal lithium batery, so is more compact than models that run off
AA batteries
Has a remote that shows the title of each track, so you can scan for the
species you want while leaving the recorder in your pocket
Allows for adjustment of recording level while recording, something the Sony
models can't do.
Unfortunately the MD-MT821 is a discontinued model, but they show up on
E-bay with some regularity for about $125.

Beast of luck, and good birding.

Jack Stephens
Edmonds, WA
jstephens62 at attbi.com