Birds

a box is on a scale, the scale shows 1000 kg. insert pidgins, now the scale shows 1050 kg. the box is air tight. pidgins scare easy, a)they start flying, without touching any of the walls. what does the scale show now? 
b) they start flying in a perfect vertical motion, hovering above the surface floor. what does thescale show now?

The scale shows the exact same, doesn't matter what the birds are doing if the box is airtight.


Obvious question is obvious