The hammerkop is an African wading bird, one of its most notable traits after its hammer like head (hence the name) is that it is an obsessive-compulsive nest builder. A pair of hammerkops will often build 3 to 5 nests a year, even if they are not breeding.
You might think that isn’t a big deal, it isn’t like bird nests are that complicated. If that is what you’re thinking then you’ve never seen a hammerkop’s nest. They are massive, sometimes approaching 5 feet across, have dense walls and a domed roof that they decorate with bright objects and sometimes other birds (such as weaver birds) will attach their nests to the exteriors. The nest itself is so strong it can support the weight of grown human, all this for a pair of birds that combined weigh about 2 pounds.