As I have previously alluded to the weight of the birds when airborne will be evenly distributed across the floor of the aircraft by the air.
How?
First, the bird in flight is in equilibrium, meaning its lift is equal to its weight.
Second, air is a gas, which means that the pressure will be evenly distributed throughout the entire aircraft. So how does the weight get distributed solely to the floor? Extending your argument, increased pressure (?) on the floor wil be accompanied by a decrease in pressure on the ceiling. When an aircraft takes off from an aircraft carrier, does the weight of the airborne aircraft transfer to the deck prior to going over the bow? Then what happens?
Cheers