Bottom up - a poo emerges in its sac. The parent grabs it and in this case she flew out of the nest with it.
Nest hygiene is vital to the health of the chicks. The only time the chicks produce a poo is directly after they have been fed and the feeding parent always hangs around for a few seconds waiting to see whether one is going to be produced. They are neatly wrapped in a little bag which the parent can remove and either eat if the chick is very young, or carry out of the nest. This is how it's done!