Clutter of Debris

One evening upon arriving from a weekend away to Taiping I think, I came back home and as i was on my way to my toilet i noticed this clutter of "stuff" atop my pot of ferns. My immediate reaction was to remove it as it look like some windblown debris had attached itself to the hanging plant. Upon closer inspection i realised that it was a little too "constructed" to be debris and i decided to leave it be. After a week later this clutter of debris look suspiciously like a nest and one fine morning i saw the culprit or rather culprits...