The discs themselves can also stand some outdoor handling, as they are cased in hard plastic. The fact that you have direct access to tracks on a minidisc is regarded as a great thing when using prepared recordings in the field, for identification of a sound you hear. You can store 199 numbered tracks. Sony and Sharp are the only minidisc field recorders that I know of, and in the mails specific reference is only made to the Sony MZ-R30. On that same minidisc website there is a comparison between the Sony and the Sharp.
Many people stress that a good microphone is at least as important as the recording device.
The speaker, for playback in the field, need not be sophisticated. The key questions is whether audio engineer Grotke's conclusions about deficiencies in the Minidisk are relevant to its application to recording and using avian vocalizations. Our conclusion, after years of using Minidiscs, is that his conclusions are not relevant. With regard to the question of using the MD in vocal analysis, as we pointed out a year and a half ago, there is a perfect analogy in the quality of calipers to measure bird skins. Judgements about an instrument's degree of precision should be relevant to the scientific task at hand.