Bird droppings with maggots?

There's a thick beam under our wooden roof gable where birds occasionally sleep at night—so, in the morning, there's perfectly normal white bird droppings on the balcony. So far, okay.
But during the day there are no birds sitting there and yet something keeps splashing onto the balcony in the same spot without me seeing a bird fly away, recently right next to me.
The "structure" – see pictures – consists of something brown and a, let's say, naked, whitish maggot (but apparently dead).
If that wasn't a bird, where else on the wooden roof or the wooden beam on the gable could it have come from? From below, all you can see is bird droppings stuck to the side of the wooden beam. And most importantly: what is that???