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The nest of the Peruvian booby is made of almost pure guano. Guano.jpg
The nest of the Peruvian booby is made of almost pure guano.
The Guanay cormorant has historically been the most important producer of guano. Leucocarbo bougainvillii qtl2.jpg
The Guanay cormorant has historically been the most important producer of guano.

Guano (from Spanish guano, from Quechua : wanu) is the accumulated excrement of seabirds and bats. As a manure, guano is a highly effective fertilizer due to its exceptionally high content of nitrogen, phosphate and potassium: nutrients essential for plant growth. Guano was also, to a lesser extent, sought for the production of gunpowder and other explosive materials. The 19th-century guano trade played a pivotal role in the development of modern input-intensive farming, but its demand began to decline after the discovery of the Haber-Bosch process of nitrogen fixing led to the production of synthetic fertilizers. The demand for guano spurred the human colonization of remote bird islands in many parts of the world. During the 20th century, guano-producing birds became an important target of conservation programs and influenced the development of environmental consciousness. Today, guano is increasingly sought after by organic farmers. [1]

Spanish language Romance language

Spanish or Castilian is a Romance language that originated in the Castile region of Spain and today has hundreds of millions of native speakers in the Americas and Spain. It is a global language and the world's second-most spoken native language, after Mandarin Chinese.

Bat Order of flying mammals

Bats are mammals of the order Chiroptera; with their forelimbs adapted as wings, they are the only mammals naturally capable of true and sustained flight. Bats are more manoeuvrable than birds, flying with their very long spread-out digits covered with a thin membrane or patagium. The smallest bat, and arguably the smallest extant mammal, is Kitti's hog-nosed bat, which is 29–34 mm (1.14–1.34 in) in length, 15 cm (5.91 in) across the wings and 2–2.6 g (0.07–0.09 oz) in mass. The largest bats are the flying foxes and the giant golden-crowned flying fox, Acerodon jubatus, which can weigh 1.6 kg (4 lb) and have a wingspan of 1.7 m.

Manure Organic matter, mostly derived from animal feces, which can be used as fertilizer

Manure is organic matter, mostly derived from animal feces except in the case of green manure, which can be used as organic fertilizer in agriculture. Manures contribute to the fertility of the soil by adding organic matter and nutrients, such as nitrogen, that are utilised by bacteria, fungi and other organisms in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web.



Paul Szpak has co-authored several journal articles claiming that seabird guano consists of nitrogen-rich ammonium nitrate and urate, phosphates, as well as some earth salts and impurities, and that unleached guano from favored locales, such as the Chincha Islands off the coast of Peru, typically contains 8 to 16 percent nitrogen (the majority of which is uric acid), 8 to 12 percent equivalent phosphoric acid, and 2 to 3 percent equivalent potash. [2] [3]

Ammonium nitrate chemical compound

Ammonium nitrate is a chemical compound, the nitrate salt of the ammonium cation. It has the chemical formula NH4NO3, simplified to N2H4O3. It is a white crystal solid and is highly soluble in water. It is predominantly used in agriculture as a high-nitrogen fertilizer. Its other major use is as a component of explosive mixtures used in mining, quarrying, and civil construction. It is the major constituent of ANFO, a popular industrial explosive which accounts for 80% of explosives used in North America; similar formulations have been used in improvised explosive devices. Many countries are phasing out its use in consumer applications due to concerns over its potential for misuse.

Uric acid chemical compound

Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a product of the metabolic breakdown of purine nucleotides, and it is a normal component of urine. High blood concentrations of uric acid can lead to gout and are associated with other medical conditions, including diabetes and the formation of ammonium acid urate kidney stones.

Phosphoric acid chemical compound

Phosphoric acid (also known as orthophosphoric acid or phosphoric(V) acid) is a weak acid with the chemical formula H3PO4. Orthophosphoric acid refers to phosphoric acid, which is the IUPAC name for this compound. The prefix ortho- is used to distinguish the acid from related phosphoric acids, called polyphosphoric acids. Orthophosphoric acid is a non-toxic acid, which, when pure, is a solid at room temperature and pressure. The conjugate base of phosphoric acid is the dihydrogen phosphate ion, H
, which in turn has a conjugate base of hydrogen phosphate, HPO2−
, which has a conjugate base of phosphate, PO3−
. Phosphates are essential for life.

However, The Association of American Plant Food Control Officers (AAPFCO) defines Seabird guano as the hardened excrement from marine birds, which contains no organic matter or nitrogen and is a source of phosphates P2O5: "P- Hydroxylapatite - is a naturally-formed phosphate rock mineral with the formula Ca5(PO4)3(OH). The Fluorine content is less than 1%." [4]

Bat guano is fecal excrement from bats. Commercially harvested bat guano is used as an organic fertilizer. [5] [6] All commercially sold bat guano is derived from insect-eating bats. [7] A study was done that demonstrated that, for fruit bats and insect bats, the composition of their guano was largely the same, and differed mainly based on their diet. [8]


Chincha Islands where guano was found in abundance. Mining was done on site and ships transported it to Europe. Chincha guano islands.JPG
Chincha Islands where guano was found in abundance. Mining was done on site and ships transported it to Europe.
Mining guano in the Chincha Islands off the central coast of Peru c. 1860. DSCN5766-guano-glantz crop b.jpg
Mining guano in the Chincha Islands off the central coast of Peru c. 1860.
Advertisement for guano, 1884 Guano advertisement 1884.jpg
Advertisement for guano, 1884

The word "guano" originates from the Andean indigenous language Quechua, which refers to any form of dung used as an agricultural fertilizer. Archaeological evidence suggests that Andean people have collected guano from small islands and points located off the desert coast of Peru for use as a soil amendment for well over 1,500 years. Spanish colonial documents suggest that the rulers of the Inca Empire assigned great value to guano, restricted access to it, and punished any disturbance of the birds with death. The Guanay cormorant has historically been the most abundant and important producer of guano. Other important guano producing species off the coast of Peru are the Peruvian pelican and the Peruvian booby. [1] [3]

Peru republic in South America

Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the west by the Pacific Ocean. Peru is a megadiverse country with habitats ranging from the arid plains of the Pacific coastal region in the west to the peaks of the Andes mountains vertically extending from the north to the southeast of the country to the tropical Amazon Basin rainforest in the east with the Amazon river.

Inca Empire empire in pre-Columbian America

The Inca Empire, also known as the Incan Empire and the Inka Empire, was the largest empire in pre-Columbian America. Its political and administrative structure is considered by most scholars to have been the most developed in the Americas before Columbus' arrival. The administrative, political and military center of the empire was located in the city of Cusco. The Inca civilization arose from the Peruvian highlands sometime in the early 13th century. Its last stronghold was conquered by the Spanish in 1572.

Guanay cormorant species of bird

The Guanay cormorant or Guanay shag is a member of the cormorant family found on the Pacific coast of Peru and northern Chile. After breeding it spreads south to southern parts of Chile and north to Ecuador, and has also been recorded as far north as Panama and Colombia – probably a result of mass dispersal due to food shortage in El Niño years. Its major habitats include shallow seawater and rocky shores.

In November 1802, Alexander von Humboldt first encountered guano and began investigating its fertilizing properties at Callao in Peru, and his subsequent writings on this topic made the subject well known in Europe. During the guano boom of the nineteenth century, the vast majority of seabird guano was harvested from Peruvian guano islands, but large quantities were also exported from the Caribbean, atolls in the Central Pacific, and islands off the coast of Namibia, Oman, Patagonia, and Baja California. At that time, massive deposits of guano existed on some islands, in some cases more than 50 m deep. [9] In this context the United States passed the Guano Islands Act in 1856, which gave U.S. citizens discovering a source of guano on an unclaimed island exclusive rights to the deposits. Nine of these islands are still officially U.S. territories. [10] Control over guano played a central role in the Chincha Islands War (1864–1866) between Spain and a Peruvian-Chilean alliance. Indentured workers from China played an important role in guano harvest. The first group of 79 Chinese workers arrived in Peru in 1849; by the time that trade ended a quarter of a century later, over 100,000 of their fellow countrymen had been imported. There is no documentary evidence that enslaved Pacific Islanders participated in guano mining. [11] Between 1847 and 1873, there was a significant increase in Peruvian guano exports, and the revenue from this momentarily ended the fiscal necessity of the colonial head tax. [12]

Alexander von Humboldt Prussian geographer, naturalist and explorer

Friedrich Wilhelm Heinrich Alexander von Humboldt was a Prussian polymath, geographer, naturalist, explorer, and influential proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister, philosopher, and linguist Wilhelm von Humboldt (1767–1835). Humboldt's quantitative work on botanical geography laid the foundation for the field of biogeography. Humboldt's advocacy of long-term systematic geophysical measurement laid the foundation for modern geomagnetic and meteorological monitoring.

Callao City in Peru

El Callao is a seaside city on the Pacific Ocean in the Lima metropolitan area. Callao is Peru's chief seaport and home to its main airport, Jorge Chávez International Airport. Callao municipality consists of the whole Callao Region, which is also coterminous with the Province of Callao. Founded in 1537 by the Spanish, the city has a long naval history as one of the main ports in Latin America and the Pacific, as it was one of vital Spanish towns during the colonial era. Central Callao is about 15 km (9.3 mi) west of the Historic Centre of Lima.

Namibia republic in southern Africa

Namibia, officially the Republic of Namibia, is a country in southern Africa. Its western border is the Atlantic Ocean; it shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and east. Although it does not border Zimbabwe, less than 200 metres of the Zambezi River separates the two countries. Namibia gained independence from South Africa on 21 March 1990, following the Namibian War of Independence. Its capital and largest city is Windhoek, and it is a member state of the United Nations (UN), the Southern African Development Community (SADC), the African Union (AU), and the Commonwealth of Nations.

After 1870, the use of Peruvian guano as a fertilizer was eclipsed by saltpeter in the form of caliche extraction from the interior of the Atacama Desert, not far from the guano areas. During the War of the Pacific (1879–1883) Chile seized much of the guano as well as Peru's nitrate-producing area, enabling its national treasury to grow by 900% between 1879 and 1902 thanks to taxes coming from the newly acquired lands. [13] Contrary to popular belief, seabird guano does not have high concentrations of nitrates, and was never important to the production of explosives; bat and cave-bird deposits have been processed to produce gunpowder, however. High-grade rock phosphate deposits are derived from the remobilization of phosphate from bird guano into underlying rocks such as limestone. [14] In 1990 a group of French researchers, from isotope studies, proposed a marine sedimentation origin for some high-grade phosphate deposits on Nauru. [15] [16]

Since 1909, when the Peruvian government took over guano extraction for use by Peru farmers, the industry has relied on production by living populations of marine birds. U.S. ornithologists Robert Cushman Murphy and William Vogt promoted the Peruvian industry internationally as a supreme example of wildlife conservation, while also drawing attention to its vulnerability to the El Niño phenomenon. South Africa independently developed its own guano industry based on sustained-yield production from marine birds during this period, as well. Both industries eventually collapsed due to pressure from overfishing. [1] The importance of guano deposits to agriculture elsewhere in the world faded after 1909 when Fritz Haber developed the Haber-Bosch process of industrial nitrogen fixation, which today generates the ammonia-based fertilizer responsible for sustaining an estimated one-third of the Earth's population. [17]

DNA testing has suggested that new potato varieties imported alongside Peruvian seabird guano in 1842 brought a virulent strain of potato blight that began the Irish Potato Famine. [18] [19]


A herring gull (Larus argentatus) excreting waste near Ile-de-Brehat. DefecatingSeagull.jpg
A herring gull (Larus argentatus) excreting waste near Île-de-Bréhat.

The ideal type of guano is found in exceptionally dry climates, as rainwater volatilizes and leaches nitrogen-containing ammonia from guano. In order to support large colonies of marine birds and the fish they feed on, these islands must be adjacent to regions of intense marine upwelling, such as those along the eastern boundaries of the Pacific and South Atlantic Oceans. [9]

Bat guano is usually mined in caves and this mining is associated with a corresponding loss of troglobytic biota and diminishing of biodiversity. Guano deposits support a great variety of cave-adapted invertebrates, that rely on bat feces as their sole source of nutrition. In addition to the biological component, deep guano deposits from birds and bats contain local paleoclimatic records and evidence of other environmental changes in strata that have built up over thousands of years, which are unrecoverable once disturbed. [20] However, when done with caution, extraction of guano can be done alongside marine bird colonies without causing them significant harm. [21] [22]

Post-depositional decomposition and ammonia volatilization of penguin guano also plays an important role in the evolution of ornithogenic sediments in the cold and arid environment of Antarctica (McMurdo Sound of the Ross Sea region, East Antarctica). [23]


In agriculture and gardening guano has a number of uses, including as: soil builder, lawn treatments, fungicide (when fed to plants through the leaves), nematicide (decomposing microbes help control nematodes), and as composting activator (nutrients and microbes speed up decomposition). [24]

"Guano's historical significance was as much cultural as it was ecological and economic." [25] References to guano in popular culture are an important sign of this cultural influence, especially regarding the ongoing relationship between guano and colonialism. In his 1845 poem "Guanosong", Joseph Victor von Scheffel used a humorous verse to take a position in the then-popular polemic against Hegel's Naturphilosophie . The poem starts with an allusion to Heinrich Heine's Lorelei and may be sung to the same tune. [26] The poem ends however with the blunt statement of a Swabian rapeseed farmer from Böblingen who praises the seagulls of Peru as providing better manure even than his fellow countryman Hegel. This refuted the widespread Enlightenment belief that nature in the New World was inferior to the Old World. The poem has been translated by, among others, Charles Godfrey Leland. [27]

See also


Related Research Articles

Fertilizer Substance added to soils to supply plant nutrients for a better growth

A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soils or to plant tissues to supply one or more plant nutrients essential to the growth of plants. Many sources of fertilizer exist, both natural and industrially produced.

Eutrophication ecosystem response to the addition of substances

Eutrophication, or hypertrophication, is when a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of plants and algae. This process may result in oxygen depletion of the water body. One example is an "algal bloom" or great increase of phytoplankton in a water body as a response to increased levels of nutrients. Eutrophication is often induced by the discharge of nitrate or phosphate-containing detergents, fertilizers, or sewage into an aquatic system.

Much of the pre-history of Peru has been wrapped up in where the farmable land was located. The most populated coastal regions of Peru are the two parallel mountain ranges and the series of 20 to 30 rivers running through the coastal desert. In dry periods only the mountains are wet enough for agriculture and the desert coast is empty, while in wet periods many cultures have thrived along the rivers of the coast. The well known Inca were a mountain-based culture that expanded when the climate became more wet, often sending conquered peoples down from the mountains into unfarmed but farmable lowlands. In contrast, the Moche were a lowland culture that died out after a strong El Niño, which caused abnormally high rainfall and floods, which was followed by a long drought.

Phosphorite non-detrital sedimentary rock which contains high amounts of phosphate bearing minerals

Phosphorite,phosphate rock or rock phosphate is a non-detrital sedimentary rock which contains high amounts of phosphate minerals. The phosphate content of phosphorite (or grade of phosphate rock) varies greatly, from 4% to 20% phosphorus pentoxide (P2O5). Marketed phosphate rock is enriched ("beneficiated") to at least 28%, often more than 30% P2O5. This occurs through washing, screening, de-liming, magnetic separation or flotation. By comparison, the average phosphorus content of sedimentary rocks is less than 0.2%. The phosphate is present as fluorapatite Ca5(PO4)3F typically in cryptocrystalline masses (grain sizes < 1 μm) referred to as collophane-sedimentary apatite deposits of uncertain origin. It is also present as hydroxyapatite Ca5(PO4)3OH or Ca10(PO4)6(OH)2, which is often dissolved from vertebrate bones and teeth, whereas fluorapatite can originate from hydrothermal veins. Other sources also include chemically dissolved phosphate minerals from igneous and metamorphic rocks. Phosphorite deposits often occur in extensive layers, which cumulatively cover tens of thousands of square kilometres of the Earth's crust.

Organic fertilizer Fertilizer developed from natural processes

Organic fertilizers are fertilizers derived from animal matter, animal excreta (manure), human excreta, and vegetable matter. Naturally occurring organic fertilizers include animal wastes from meat processing, peat, manure, slurry, and guano.


Fertigation is the injection of fertilizers, used for soil amendments, water amendments and other water-soluble products into an irrigation system.

McKean Island island

McKean Island is a small, uninhabited island in the Phoenix Islands, Republic of Kiribati. It is located at 3°36′S174°07′W. Its area is 57 hectares.

Maximilian Joseph August Schlemmer, known as the "King of Laysan," was a German immigrant to the United States who settled in Hawaii and spent fifteen years from 1894 to 1915 living with his family on the Hawaiian island of Laysan as superintendent of a guano mining operation. Schlemmer was interested in the birdlife of the island and made several studies which provide information on historic bird populations. However, Schlemmer and his family unwittingly introduced rabbits to Laysan, leading to the extinction of the Laysan rail and Laysan millerbird and permanently changed the island's ecology in the early 20th century. A biography of Schlemmer was written by his grandson, Tom Unger.

Peak phosphorus Point in time of the maximum phosphorus production

Peak phosphorus is a concept to describe the point in time when humanity reaches the maximum global production rate of phosphorus as an industrial and commercial raw material. The term is used in an equivalent way to the better-known term peak oil. The issue was raised as a debate on whether a "peak phosphorus" was imminent or not around 2010, but was largely dismissed after USGS and other organizations increased the world estimates on available phosphorus resources.

Bat Cave mine

The Bat Cave guano mine, located in the western Grand Canyon of Arizona at river mile 266, 800 feet (240 m) above Lake Mead, was an unusual, expensive and noteworthy mining operation. The natural cave was a bat habitat and contained an accumulation of guano.

The Guano Era refers to a period of stability and prosperity in Peru during the mid-19th century. It was sustained on the substantial revenues generated by the export of guano and the strong leadership of president Ramón Castilla. The starting date for the guano era is commonly considered to be 1845, the year in which Castilla started his first administration. It ended shortly after the war between Spain and Peru in 1866.

Taranakite phosphate mineral

Taranakite is a hydrated alkali iron-aluminium phosphate mineral with chemical formula (K,Na)3(Al,Fe3+)5(PO4)2(HPO4)6·18H2O. It forms from the reaction of clay minerals or aluminous rocks with solutions enriched in phosphate derived from bat or bird guano or, less commonly, from bones or other organic matter. Taranakite is most commonly found in humid, bat inhabited caves near the boundary of guano layers with the cave surface. It is also found in perennially wet coastal locations that have been occupied by bird colonies. The type location, and its namesake, the Sugar Loaf Islands off Taranaki, New Zealand, is an example of a coastal occurrence.

The history of fertilizer has largely shaped political, economic, and social circumstances in their traditional uses. Subsequently, there has been a radical reshaping of environmental conditions following the development of chemically synthesized fertilizers.

Many countries have standardized the labeling of fertilizers to indicate their contents of major nutrients. The most common labeling convention, the NPK or N-P-K label, shows the amounts of the chemical elements nitrogen, phosphorus, and potassium.


Huanillos is a small seaside village in Chile and a big source of huano (guano) in the 19th century.

The history of the Haber process begins with the invention of the Haber process at the dawn of the twentieth century. The process allows the economical fixation of atmospheric dinitrogen in the form of ammonia, which in turn allows for the industrial synthesis of various explosives and nitrogen fertilizers, and is probably the most important industrial process ever developed during the twentieth century.

Lobos de Tierra island in Peru

Lobos de Tierra is a Peruvian island situated 19 km from the mainland close to the Illescas Peninsula and the boundary between the departments of Piura and Lambayeque regions. Its area is 16 km², its approximate length is 10 km, and its approximate width is 3 km.

Peruvian nitrate monopoly

The Peruvian nitrate monopoly was a state-owned enterprise over the mining and sale of saltpeter created by the government of Peru in 1875 and operated by the Peruvian Nitrate Company. Peru intended for the monopoly to capitalize on the world market's high demand for nitrates, thereby increasing the country's fiscal revenues and supplementing the financial role that guano sales had provided for the nation during the Guano Era (1840s-1860s).

Guañape Islands islands in Peru

The Guañape Islands are an island group off the coast of northern Peru. It consists of four islands: Isla Guañape Norte, Isla Guañape Sur, Islotes Cantores and Islotes Los Leones.


  1. 1 2 3 Cushman, Gregory T. (2013). Guano and the Opening of the Pacific World: A Global Ecological History. Cambridge University Press. ISBN   9781107004139.
  2. Szpak, Paul; Longstaffe, Fred J.; Millaire, Jean-Francois; White, Christine D. (2012). "Stable Isotope Biogeochemistry of Seabird Guano Fertilization: Results from Growth Chamber Studies with Maize (Zea mays)". PLoS One . 7 (3): e33741. doi:10.1371/journal.pone.0033741.
  3. 1 2 Szpak, Paul; Millaire, Jean-Francois; White, Christine D.; Longstaffe, Fred J. (2012). "Influence of seabird guano and camelid dung fertilization on the nitrogen isotopic composition of field-grown maize (Zea mays)". Journal of Archaeological Science . 39 (12): 3721–3740. doi:10.1016/j.jas.2012.06.035.
  4. "Association of American Plant Food Control Officials Terms & Definitions Committee 2018 Summer Annual Meeting Report". Association of American Plant Food Control Officials (AAPFCO) USA, August 2 2018. Retrieved on 27 January 2019.
  5. "Bat Guano Definition". Association of American Plant Food Control Officials (AAPFCO), Oregon Department of Agrigulture. USA, 31 March 2016. Retrieved on 12 December 2017.
  6. "California Department of Food and Agriculture-Notice to Fertilizing Material Licensees-Use of the term 'Bat Guano' on Fertilizing Material Labels". California Department of Food and Agriculture. USA, 11 May 2017. Retrieved on 12 December 2017.
  7. "Insect Eating (Insectivorous) Bat Guano". RealGuano. USA, 21 September 2017. Retrieved on 12 December 2017.
  8. Emerson, Justin K.; Roark, Allison M. (2007). "Composition of guano produced by frugivorous, sanguivorous, and insectivorous bats". Acta Chiropterologica. 9: 261–267. doi:10.3161/1733-5329(2007)9[261:cogpbf];2.
  9. 1 2 Hutchinson, G. Evelyn (1950). "Survey of Existing Knowledge of Biogeochemistry: 3. The Biogeochemistry of Vertebrate Excretion". Bulletin of the American Museum of Natural History. 96: 1–554.
  10. Skaggs, Jimmy (1994). The Great Guano Rush: Entrepreneurs and American Overseas Expansion. New York: St. Martin's. ISBN   978-0312103163.
  11. Méndez, Cecilia (1987). Los trabajadores guaneros del Perú, 1840–1879. Lima: Universidad Nacional Mayor de San Marcos.
  12. Larson, Brooke (2004). Trials of Nation Making: Liberalism, Race, and Ethnicity in the Andes, 1810-1910. Cambridge: Cambridge University Press. p. 146. ISBN   978-0521567305.
  13. Crow, The Epic of Latin America, p. 180
  14. McKelvey VE (1967). "A summary of the salient features of the geology of phosphate deposits, their origin, and distribution" (PDF). Geological Survey Bulletin. 1252-D. D14.
  15. Bernat M, Loubet M, Baumer A (1991). "Sur l'origine des phosphates de l'atoll corallien de Nauru" [On the origin of phosphates from the Nauru atoll](PDF). Oceanologica Acta (in French). 14 (4).CS1 maint: Uses authors parameter (link)
  16. Glenn, Craig, et al., eds. (2000). Marine Authigenesis: From Global to Microbial. Tulsa, OK.CS1 maint: Extra text: authors list (link)
  17. Wolfe, David W. (2001). Tales from the underground a natural history of subterranean life. Cambridge, Massachusetts: Perseus Pub. ISBN   978-0-7382-0128-3. OCLC   46984480.
  18. Dwyer, Jim (10 June 2001). "June 3–9; The Root of a Famine". The New York Times. p. 2.
  19. Gómez-Alpizar, Luis; et al. (2007). "An Andean origin of Phytophthora infestans inferred from mitochondrial and nuclear gene genealogies". PNAS . 104 (9): 3306–11. doi:10.1073/pnas.0611479104. PMC   1805513 . PMID   17360643.
  20. Hong Yan et al., "A 2000-year record of copper pollution in South China Sea derived from seabird excrements: a potential indicator for copper production and civilization of China," Journal of Paleolimnology 44 (2010): 431-442; Hong Yan et al., "Millennial mercury records derived from ornithogenic sediment on Dongdao Island, South China Sea," Journal of Environmental Science 23 (2011): 1415-1423.
  21. "Guañape Sur trailer", IcarusFilmsNY.
  22. "Islas Guañape trailer", El Peru canta y baila.
  23. Nie, Yaguang; Liu, Xiaodong; Wen, Tao; Sun, Liguang; Emslie, Steven D. (2014). "Environmental implication of nitrogen isotopic composition in ornithogenic sediments from the Ross Sea region, East Antarctica: Δ15N as a new proxy for avian influence". Chemical Geology. 363: 91–100. doi:10.1016/j.chemgeo.2013.10.031.
  24. "h2g2 - Seabird Guano and Bat Dung". Retrieved 26 January 2013.
  25. Guano and the Opening of the Pacific World: A Global Ecological History, Gregory T. CushmanCambridge University Press, 25.03.2013, p. 51
  26. Note: A scan of the Loreley sheet music and lyrics (printed in 1859; note the spelling "Lorelei") are available on the commons in three images: File:Lorelei1.gif, File:Lorelei2.gif, File:Lorelei3.gif
  27. Charles Godfrey Leland, Gaudeamus! Humorous Poems by Joseph Viktor von Scheffel, Ebook-Nr. 35848 on

Further reading





Wiktionary-logo-en-v2.svg The dictionary definition of guano at Wiktionary