Microphone self-noise versus background noise

["Bruce" rideout_bruce]

I've been going through the group archives trying to get a better understan=
ding of the relative importance of microphone self noise versus low-frequen=
cy background noise in bird sound recordings. I understand that the Sennhei=
ser MKH series has much lower self noise than the ME series, but I would ex=
pect that the benefit of the MKH series would only be realized if the backg=
round environmental noise could be kept lower than the microphone self nois=
e. In most of my recordings, I'm only able to keep the background noise to =
-40 DB or so because of distant road noise, airplanes, streams, and wind, s=
o my assumption is that an MKH microphone would not improve my signal-to-no=
ise ratio. However, I have seen comments here indicating that there is a no=
ticeable difference between MKH and ME series microphones even in noisy env=
ironments. Is that really the case? If so, why?

Thanks,

Bruce Rideout