Structural engineer in action

Whether you're a 'bird person' or not, this is stunning!!! Not to detract from the sheer magic of it, but in practical terms, how MANY trips would a bird have to make with that tiny little quantity of mud/clay it could carry? (and how far from the nest is the source of material?)    If you take the construction of a "circular bowl" in your stride as instinctive – how the heck does the bird come up with the windbreak/entrance design that shields the eggs/chicks from the elements – and at what point in fashioning the bowl do they start to construct it?   Even if you think you could build this?  Try it without using your hands!