guano

The latter elements suggest the hearth was intentionally sealed with a mixture of guano and sand, which can protect plant materials within the hearth from catching fire—conditions needed to create tar.

Their guano, or dung, can also be used as fertilizer.

The seabirds' droppings, known as guano, carry nitrogen and phosphorus, important nutrients that leach into the surrounding seas fertilising surrounding coral reef environments.

And so sprang up a gigantic industry dedicated to the harvesting of guano from Latin American bird colonies, where there were huge piles of the stuff.

Researchers have discovered a new avenue by which viruses may spread from bats to other mammals: in bat guano eaten by chimpanzees and other animals.