The Hamerkop (Scopus umbretta), a small African waterbird with a hammer-shaped head, is one of nature’s strangest architects. While most birds weave tidy nests just large enough for their chicks, the Hamerkop constructs enormous domed structures that can weigh over 50 kilograms and rival the bulk of a small car.

But the real eccentricity comes after the “mansion” is finished. The Hamerkop starts decorating — or perhaps hoarding — with an enthusiasm unmatched in the avian world. Old rope, bicycle springs, dented cooking pots, broken spoons, even the skulls of other animals are dragged in or hung outside like ornaments. From a distance, it can look like a junk shop suspended in the branches.

Why does it do this? Scientists aren’t entirely sure. It could be a way to impress mates, a compulsive collecting instinct, or simply the bird’s idea of fun. Whatever the reason, the result is the same: a fortress so overbuilt that several humans could stand on top of it without it collapsing, and so cluttered with oddities that it seems part museum, part fortress, part madman’s attic.

Quirky. Tireless. The undisputed hoarder-king of the bird world.