Question

It is my understanding that if you have a sealed container with a bird inside that the weight of the container will be the same, whether the bird is flying within it or perched on the floor. If the box is empty and a bird lights on it, presumably the weight increases by the weight of the bird, but if the bird is hovering just above the box, will the weight change? I guess I am wondering if weight is defined by all objects, including atmosphere, above it. I appreciate that the differences are subtle, but are they there?

thanks.