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Birds as bioindicators of pollution in aquatic and terrestrial environments

Javier Cotin

Birds have been widely used as bioindicators. In this study we face the use of birds as bioindicators of metal pollution in two different scenarios of contamination: one that takes place in an aquatic environment, the Ebro river basin, and a second that occurs in a terrestrial environment, the Bolivian Andes. 


In the case of the Ebro river basin, the pollution threat is a factory located at the river bend, close to Flix, that due to its long operational activity and along with the construction of a dam next to the plant around 1960, resulted in the accumulation of 200,000–360,000 tons of industrial wastes in the riverbed, occupying an area of 700 m of length and 60 m of width. In this study case we evaluated whether aquatic birds such as the Purple Heron reflect the potential pollutant exposure from Flix Reservoir among different riverine and deltaic areas, and assess their usefulness as bioindicators. Also we examined if the polluted wastes of Flix reservoir affect the levels of pollution of the habitats where waterbird populations of the Ebro Delta (situated 90 km downstream) forage and feed. 


As results stable isotopes shown the high nitrification and lower carbon signatures in the river, and together with the niche width metrics, that Common and Sandwich Tern behave as strict specialists at the Ebro Delta, with narrow niche widths, while in the opposite way, Little Tern, Little Egret, Purple Heron, Night Heron and the Moorhen behave like generalists foragers, with broad niche widths. Mercury levels in nestlings of Purple Heron at Flix site and eggs of Audouin’s Gull, Little Tern and Common Tern ‘Banya’ at the Ebro Delta are high enough to be of special concern. Arsenic (specially used in combination with carbon signatures) discriminates outstandingly between marine and freshwater species. Both eggs and nestling feathers of Purple Herons are adequate bioindicators for trace element pollution, but nestling feathers present certain advantages. The six selected blood parameters (TOSC ROO*, TOSC OH*, BhCE, CbE, LDH and MN) provide the first evidence of an association of biological responses with pollutants in heron species.


The second study case takes place in Bolivia. Anthropogenic mining has taken place in the Bolivian Andes since at least the fifteenth century. Particularly the East of Oruro Department in the Eastern Andean Cordillera is affected by a long term history of mining. These mining activities were characterized by the deposition of large tailing piles, which accumulated in abandoned and active mines, where trace metals such as lead, arsenic, cadmium, and antimony could reach surface waters and soils, and so the biota. In this case we evaluated the potential of Tinamou species as sentinels of exposure to local trace metal pollution and studied different routes of lead accumulation into the sentinel species, in order to assess the usefulness of feather levels as a measure of the exposure to this pollutant.


As results we found that the detected small home ranges detected in Ornate Tinamou (lower than 1 km2) and their sedentary habits make of this species an adequate bioindicator of local pollution. We recommend feathers for future monitoring programs as they are a non invasive sample. Higher rates of histopathological damage were found in kidney at the polluted sites. We detected high levels of trace elements detected at the polluted sites in the two studied species of Tinamou (Ornate and Darwin Tinamou), many of them trespassing hazard levels. The calamus is the most suitable section for assessing the original endogenous lead levels in feather samples.

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Trace metals (Hg, Pb, and Cd) in feathers of four Galapagos waterbird species

E.S. Jimenezi, G. Jimenez-Uzcategui, D.A. Egasi, N. Solis, P. Carrera-Jativa, R. L. Vinueza, J. Cotin, A. Nieto, C. Garcia, C. Sevilla & D. Rueda

Marine Ornithology 48: 85–89 / 2020

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Using referential values of δ13C AND δ15N to infer the foraging ecology of Galapagos seabirds

G. Jimenez-Uzcátegui, L. Vaca, J. Cotin, C. García, A. Costales, C. Sevilla & D. Paez-Rosas. 

Marine Ornithology 47: 5–10 / 2019 

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Survival and extinction of breeding landbirds on San Cristóbal, a highly degraded island in the Galápagos

M. Dvorak, B. Fessl, E. Nemeth, D. Anchundia, J. Cotin, C.H. Shulze, W. Tapia & B. Wendelin

Bird Conservation International, 1-15. / 2019


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Lead and cadmium levels in Galapagos Penguin Spheniscus mendiculus, Flightless cormorant Phalacrocorax harrisi and Waved albatross Phoebastria irrorata

G. Jiménez-Uzcátegui, R.L. Vinueza, A.S. Urbina, D.A. Egas, C. García, J. Cotín & C. Sevilla

Marine Ornithology 45: 159–163 / 2017

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The diet of great tit nestling: Comparing observation records and stable isotope analyses

E. Pagani-Nuñez, M. Renom, F. Mateos, J. Cotín & J.C. Senar

Basic and Applied Ecology 18: 57–66 / 2017

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Metals exposure influences the melanin and carotenoid-based coloration in great tits

M. Giraudeau, F. Mateos-Gonzalez, J. Cotín, E. Pagani-Nuñez, A. Torné-Noguera & J.C. Senar

Science of the Total Environment 532:512–516 / 2015

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Are the toxic sediments deposited at Flix reservoir affecting the Ebro river biota? Purple Heron eggs and nestlings as indicators

J. Cotin, Manuel García-Tarrasón, Carolina Sanpera & Lluis Jover

Ecotoxicology 21:1391–1402 / 2012

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Sea, freshwater or saltpans? Foraging ecology of terns to assess mercury inputs in a wetland landscape: the Ebro Delta

J. Cotin, Manuel García-Tarrasón, Carolina Sanpera, Lluis Jover & Xavier Ruiz

Estuarine, Coastal and Shelf Science 92:188-194 / 2011 

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Blood biomarkers and contaminant levels in feathers and eggs to assess environmental hazards in heron nestlings from impacted sites in Ebro basin 

C. Barata, M.C. Fabregat, J. Cotín, D. Huertas, M. Solé, L. Quirós, C. Sanpera, L. Jover, X. Ruiz, J.O. Grimalt & B. Piña 

Environmental Pollution 158(3):704-10 / 2010 

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Trace metal concentrations in tissues of two tinamou species in mining areas of Bolivia and their potential as environmental sentinels 

Á. Garitano-Zavala, J. Cotín, M. Borrás & J. Nadal 

Environmental Monitoring and Assessment 168:629–644 / 2010 

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Home range extension and overlap of the Ornate Tinamou (Nothoprocta ornata) in an Andean agro-ecosystem

Á. Garitano-Zavala, Z. Chura, J. Cotín, X. Ferrer & J. Nadal

The Wilson Journal of Ornithology 125(3):491-501/ 2013

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Development of optimal survey methods to provide reliable estimates of game bird populations on Hawai‘i Island

J. Cotín, C. Wilhite, S. Hornavar, I.W. Cole, K. Sproat & M.R. Price

Report ​for the State of Hawai'i Department of Land and Natural Resources, Division of Forestry and Wildlife

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Breeding phenology and daily activity of the Hawaiian Short-eared Owl (Asio flammeus sandwichensis) on O'ahu 

J. Cotín, K.E. Davis, A.A. Siddiqi & M.R. Price

Report ​for the State of Hawai'i Department of Land and Natural Resources, Division of Forestry and Wildlife

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Population size, distribution and habitat use of the Hawaiian Short-eared Owl (Asio flammeus sandwichensis) on O'ahu

M. Price & J. Cotín

Report ​for the State of Hawai'i Department of Land and Natural Resources, Division of Forestry and Wildlife

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Squacco Heron

J. Cotin / Editors: S. Herrando · L. Brotons · J. Estrada · S. Guallar & M. Anton / Published by Lynx Edicions and Institud Català d'Ornitologia 

Catalan Winter Bird Atlas 2006 - 2009

“Ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science.” 

– Charles Darwin

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