Seabird Guano Helped Build the Ancient Chincha Kingdom

A new study indicates that seabird droppings had an unexpectedly pivotal part in the development of one of ancient Peru’s most influential societies.

According to the researchers, this natural fertiliser increased maize output, reinforced the economy and may even have supported the Chincha Kingdom’s rise centuries before the Inca.

Jacob Bongers, a digital archaeologist at the University of Sydney and Visiting Research Fellow at the Australian Museum Research Institute, led the research.

After analysing ancient maize remains alongside archaeological evidence from Peru’s Chincha Valley, the team concluded that fertilisation with guano created agricultural surpluses that supported commerce, prosperity and political power.

Fertiliser behind prosperity

The research shows that a resource which may appear unremarkable today was once enormously significant in the Andes.

“Seabird guano may seem trivial, yet our study suggests this potent resource could have significantly contributed to sociopolitical and economic change in the Peruvian Andes,” Bongers said.

Guano – nutrient-dense seabird droppings containing compounds such as nitrogen – substantially raised maize yields, and this increased production had far-reaching effects on Chincha society.

By greatly expanding maize production, it supported the Chincha Kingdom’s economy, trade, population growth and alliance with the Inca Empire.

Farming traces preserved in buried maize

To establish how extensively guano was used, the researchers studied 35 maize samples recovered from burial tombs in the Chincha Valley. This coastal area once sustained roughly 100,000 people.

The maize contained exceptionally high nitrogen levels – well beyond what local soils could produce naturally – providing strong evidence that farmers treated their crops with seabird guano.

This nutrient-rich substance is produced by seabirds that eat marine life, accounting for its unusually high nitrogen concentration.

Communities probably collected seabird guano from the nearby Chincha Islands, which have long been recognised for their plentiful, high-quality deposits.

Historical sources likewise describe people across coastal Peru and northern Chile travelling by raft to nearby islands to gather seabird droppings for use as fertiliser.

Seabirds and Chincha Kingdom culture

The researchers also went beyond chemical evidence, studying textiles, ceramics, carvings and paintings that show seabirds, fish and germinating maize together.

Such depictions imply that the connection between birds and farming carried symbolic as well as cultural significance.

“Together, the chemical and material evidence we studied confirms earlier scholarship showing that guano was deliberately collected and used as a fertilizer,” said Bongers.

The results further suggest a profound cultural importance. They show that communities understood the extraordinary value of guano fertiliser and deliberately celebrated, safeguarded and even ritualised the link between seabirds and agriculture.

Evidence broadens the history of seabird guano

The study combined several forms of evidence, including historical documentation and biochemical analysis. The researchers said this wide-ranging method clarified both the purposes and methods of guano use.

“The historical records documenting how bird guano was applied to maize fields helped us interpret the chemical data and understand the regional importance of this practice,” said Emily Milton, a postdoctoral fellow at the Smithsonian Institution.

“Our work extends the known geographic extent of guano fertilization, echoing recent findings in northern Chile, and suggests soil management began at least around 800 years ago in Peru.”

Agriculture on desert coasts

Farming on Peru’s coast has always posed major challenges. The area is exceptionally arid, while even irrigated land rapidly loses nutrients. Keeping farmland productive demands continual work.

Guano sourced from neighbouring islands provided a renewable, highly efficient answer. It enabled Chincha Valley farmers to cultivate substantial quantities of maize, among the Americas’ most important staple foods.

The surpluses that followed helped support specialist workers, including traders, farmers and fisherfolk. This economic foundation assisted the Chincha in becoming leading merchants along the coast.

“We know the Chincha were extraordinarily wealthy and one of the most powerful coastal societies of their time. But what underpinned that prosperity? Previous research often pointed to spondylus shells, the spiny oyster, as the key driver of merchant wealth,” Bongers said.

“Guano was central to the Chincha Kingdom’s success, with the Chincha’s maritime knowledge and access to the Chincha Islands likely reframing their strategic importance in the region.”

Chincha Kingdom alliances

The findings also offer insight into the relationship between the Chincha Kingdom and the Inca Empire. The Inca, whose base was in the Andean highlands, depended strongly on maize as food and to make chicha, a ceremonial fermented beer.

However, maize cultivation was difficult at high altitudes, while the Inca had limited maritime capabilities.

“Guano was a highly sought-after resource the Incas would have wanted access to, playing an important role in the diplomatic arrangements between the Inca and the Chincha communities,” said Bongers.

“It expanded Chincha’s agricultural productivity and mercantile influence, leading to exchanges of resources and power.”

Rethinking wealth in the ancient Andes

The study also calls for a wider reassessment of what constituted wealth in ancient societies. Rather than considering only valuable materials such as gold and silver, it underlines the value of ecological expertise and resource management.

“The true power of the Chincha wasn’t just access to a resource; it was their mastery of a complex ecological system,” said co-author Jo Osborn from Texas A&M University.

“They possessed the traditional knowledge to see the connection between marine and terrestrial life, and they turned that knowledge into the agricultural surplus that built their kingdom.”

“Their art celebrates this connection, showing us that their power was rooted in ecological wisdom, not just gold or silver.”

Lessons from the Chincha Kingdom

The findings build on Bongers’ earlier research into the Band of Holes, an archaeological location south of the Chincha Valley. He considers the site to have been an ancient marketplace constructed by the Chincha Kingdom.

“This research adds another layer to our understanding of how the Chincha, and potentially other coastal communities, used resources, trade and agriculture to expand their influence,” Bongers said.

Taken together, the evidence provides a striking account of how one simple natural resource helped form an entire society. In the ancient Andes, power did not arise solely from armies or precious metals – at times, it came from the sea, the birds and the fertile fields they enabled.