Guano and Peruvian birds
A new study has revealed that seabird guano fueled the rise of Peru’s powerful Chincha Kingdom.
In 1532, in the city of Cajamarca, Peruthe Spanish conqueror Francisco Pizarro and a group of Europeans made the Inca ruler Atahualpa hostagepreparing the ground for the fall of the Inca Empire.
Before this fateful attack, Francisco’s brother, Pedro Pizarromade a curious observation: besides the Inca himself, the Lord of Chincha was the only person in Cajamarca transported in a litter, a transport platform.
Why did the Lord of Chincha hold such a high position in Inca society? A new study, this Wednesday in PLOS Onefound evidence of a Surprising potential source of power and influence: bird poop.
A powerful and precious resource
chinchain southern Peru, is one of several river valleys along the desert coast fed by waters from the Andean highlands, which have long been central to irrigation agriculture. About 25 kilometers out to sea are the Chincha Islands, with the largest Pacific guano deposits.
Seabird guano, or excrement, is a highly potent organic fertilizer. Compared to land manures like cow manure, guano contains much more nitrogen and phosphorus, which are essential for plant growth.
On the Peruvian coast, the Humboldt/Peru ocean current creates rich fishing areas. These fishing areas support huge colonies of seabirds that nest on the rocky offshore islands.
Thanks to the dry climate, with almost no rain, seabird guano is not washed away, but continues to accumulate until it reaches many meters in height. This unique environmental combination makes the particularly valued Peruvian guano.
The study combines iconography, historical written accounts and the analysis of stable isotopes of archaeological corn – Zea mays – to demonstrate that indigenous communities in the Chincha Valley have used seabird guano for at least 800 years to fertilize crops and increase agricultural production.
We suggest that guano likely shaped the rise of the Chincha Kingdom and its eventual relationship with the Inca Empire.
Lords of the desert coast
The Chincha Kingdom (1000–1400 CE) was a large-scale society composed of a population estimated at 100,000 people.
It was organized into specialized communities such as fishermen, farmers and traders. This society controlled the Chincha Valley until it was integrated into the Inca Empire in the 15th century.
Given the proximity of the historically important guano deposits on the Chincha Islands, Peruvian historian Marco Curatola proposed in 1997 that seabird guano was an important source of Chincha’s wealth.
A biochemical test
Biochemical analysis is a reliable way to identify past fertilizer use. A 2012 experimental study showed that plants fertilized with manure from camelids (alpacas and llamas) and seabirds have higher nitrogen isotope values than unfertilized crops.
In the new study, 35 corn samples recovered from graves in the Chincha Valley, documented as part of a previous study on burial practices, were analyzed.
Most samples had higher nitrogen isotope values than expected for unfertilized corn, suggesting that some form of fertilization had occurred. About half of the samples had extremely high values.
This chemical analysis confirms the use of guano in pre-Hispanic cultures.
Images and written fonts
Guano – and the birds that produce it – also had a broader meaning for the Chincha people.
Analysis of archaeological artifacts suggests that the Chincha people had a deep understanding of the connection between land, sea and sky. His use of guano and his relationship with the islands were not just a practical choice; they were deeply rooted in his worldview.
This reverence is reflected in Chincha material culture. In his textiles, ceramics, architectural friezes and metallic objects, repeated images of seabirds, fish, waves and germinating corn are seen.
These images demonstrate that the Chincha understood the entire ecological cycle: seabirds ate ocean fish and produced guano, guano fed corn, and corn fed people.
The power of… poop!
As an effective and highly valuable fertilizer, guano also allowed Chincha communities increase crop yields and expand trade networkscontributing to the economic expansion of the Chincha Kingdom.
We suggest that fishermen sailed to the Chincha Islands to obtain guano and then supplied it to farmers as well as maritime traders to trade it along the coast and into the mountainous interior.
Chincha’s agricultural productivity and growing mercantile influence would have reinforced its strategic importance for the Inca Empire. Around 1400 AD, the Incas incorporated Chincha after a “peaceful” capitulation, creating one of the few calculated alliances of its kind.
Although the “agreement” established between Chincha and the Incas remains under debate, the new study that seabird guano played a role in these negotiationss, as the Inca state was interested in corn but did not have access to marine fertilizers.
This could explain why the Lord of Chincha was held in such high regard that he was carried in a litter, as Pedro Pizarro noted.
The Incas came to value this fertilizer so much that they imposed restrictions on access to the guano islands during the breeding season and prohibited the killing of guano birds, on or outside the islands, under penalty of death.
