pseudonym58 Yes. And it is generated by the circuit inside the field recorder. When you change mic level, the amplitude of this noise is not changed.
So, let's say your recorder has a white noise of -45 dBFS. If you set your mic level very low and the real sound recorded averages -35 to -40 dBFS, then the white noise will be quite audible relative to real sound. If you set your mic level high so that real sound is recorded to be -12 to -6 dBFS, then the white noise (still -45 dB) become almost inaudible relatively.
In field recording of nature sound, this become a problem because you can turn up the mic level to max, and the recorded sound still won't be loud enough to overpower the white noise in the recorder. TASCAM field recorders are notorious for this problem. Zoom might be slightly better. SONY is much better hands down, but they are also many times more expensive for this reason.