Roger's questions
1) Birds in helicopter are supported by air, which is supported by helicopter. Or, if the birds are near the doors, their downwash might be outside the helicopter, and helicopter does not "feel" their weight. See previous posts.
2) Is the aircraft at terminal velocity? Speed is irrelevant, acceleration is not. Aircraft accelerating? Pilot feels weightless, or at least lighter than normal. Aircraft constant speed? It may as well be stationary for all the pilot knows. Think of an aircraft in a steep high speed descent - are you lighter? See previous posts on geostationary satellites, men on their way to moon etc.
O8