What does guano mean?
Guano is the accumulated excrement of birds, bats, and sometimes fish. Although the word can sound blunt or even comic in casual reference to droppings, it is a precise and important term in agriculture, geology, ecology, and conservation. Historically, seabird colonies on South American islands yielded vast deposits of guano, which was collected as a nitrogen- and phosphorus-rich fertilizer and shipped to farming regions worldwide. Today, the word also refers to fertilizer made from such material and to phosphate deposits formed from ancient bird droppings. Guano supports nutrient cycles and provides food for insects and microorganisms, while large quantities can alter habitats near nesting or roosting sites. In formal dictionaries, guano can also be a rare verb meaning to fertilize with guano. In general writing, use it when the source of the material matters; for ordinary animal droppings, “droppings” or “dung” is usually more idiomatic.
The excrement of birds, bats, and sometimes fish, especially when accumulated for use as fertilizer; also, fertilizer made from such excrement or phosphate-rich deposits.
"Cave explorers discovered ancient bat guano deep inside the passage."
Usually treated as a mass noun, though “guanos” can refer to distinct deposits or kinds.
To fertilize land with guano.
"Farmers guanoed their fields before planting."
Rare and technical; ordinarily expressed as “fertilize with guano.”
The mass noun is commonly left unchanged, while the plural “guanos” is used for distinct deposits or kinds of guano.
"The researchers compared guano samples from several seabird colonies."
Guano turned seabird colonies into some of the world's most valuable fertilizer mines.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does guano come from?
The English word entered English in the early 17th century from Spanish guano, a term for droppings or fertilizer. Spanish had borrowed it from Quechua huano, with the modern Quechua form wanu also recorded. The international spread of the word reflects the historical trade in guano, especially the exploitation of South American seabird deposits during the 19th century.
Related word forms
How guano is actually used
Guano is normally an uncountable mass noun, although the plural “guanos” is used for distinct deposits or kinds. In informal contexts, the word can sound blunt when referring to ordinary bird droppings. The verb is rare and technical; “fertilize with guano” is usually more natural.