I know some do, but I don't know if that applies to all species.
All birds molt.
QUAD
pakistan
cows and dogs
There is not really any thing since they eat 'on-the-wing'. In other words they eat insects, mainly flying ones.
collapsing barns
By flying i suppose.
paint the ceiling sky blue
No, the barn swallow, Hirundo Rustica, is a very common species, in no way endangered.
Owls are predators no animal eats owls . But barn owls do swallow their prey whole.
Mud swallows build nests both during the day and night. Barn swallows are also known to do the same thing.
they have wings
About 4 per nest.