Guanay Cormorant Leucocarbo bougainvilliorum


Justification of Red List Category
This species is suspected to have experienced moderately rapid declines in the past three generations (33 years), and as a result it is classified as Near Threatened.

Population justification
Zavalaga and Paredes (1999) estimated the population at 3.7 million individuals, hence the population is best placed in the band 2,500,000-4,999,999 individuals.

Trend justification
The species has fluctuated in numbers in the past, but overall declines in the region of 20-29% are suspected in the past three generations (33 years).

Distribution and population

Phalacrocorax bougainvilliorum is found along the Pacific coast of Peru and northern Chile. A small population also bred on a short stretch of the Patagonian Atlantic coast of Argentina, but this appears to be ecologically extinct (Bertellotti et al. 2003). From historical times the Guanay Cormorant has been the dominant avian species in the Peruvian Coastal Current in terms of numbers and consumption of marine resources. The population in Peru was estimated as <4 million birds during the period 1909-1920; 21 million were estimated in 1954 and 3.7 million were estimated on the north-central Peruvian coast in 1996 (Zavalaga and Paredes 1999). Mass dispersal, breeding failures and temporary declines have resulted periodically from El Niño Southern Oscillation (ENSO) events, and both fish-stocks and the populations of seabirds that depend on them are adapted to these fluctuations. Although the species is now protected in Peru, and the guano industry is adequately regulated, there are concerns that this species has been badly affected by the ENSO event of 1998 (G. Engblom in litt. 2003), and that declines now approach 30% over three generations (33 years in this species).


Breeding occurs year round with most egg-laying in May-December (on the northern coast of Perú, breeding starts in May-September, on the southern coast of Perú, breeding starts October-December, Passuni et al. 2016). It breeds on offshore islands and remote coastal headlands and feeds exclusively in the inshore environment usually within 19 km of colonies (Zavalaga and Paredes 1999, Weimerskirch et al. 2012). Unlike other cormorants it is not primarily a benthic feeder but preys mainly on the schooling Peruvian anchovy Engraulis ringens, Peruvian silverside Odonthestes regia and mote sculpin Normanichythes crockeri found in the cold water of the Humboldt Current (del Hoyo et al. 1992, Zavalaga and Paredes 1999).


Several threats result from the seabird-fishery interactions, including bycatch, resource competition and direct persecution. The global extent of bycatch has not been quantified, but is thought to affect a majority of the population. When Ayala (2012) interviewed 59 fishermen working in the Peruvian anchovy fishery in 2009, 54% of them mentioned seabird bycatch, of which 10% listed Guanay Cormorant among the encountered species. Mangel (2012) reports that Guanay Cormorants and White-chinned Petrels Procellaria aequinoctialis, made up the majority of total bycatch in Peruvian surface driftnet fishery (targeting sharks and rays). The Guanay Cormorant preys almost exclusively on anchovies (Tovar and Guillén 1987, Barbraud et al. 2017) and is therefore vulnerable to competition for food with the industrial fishery, resulting in food limitation. Barbraud et al. (2017) found that the proportion of anchovy biomass removed by fishing is negatively correlated to the abundance of Guanay Cormorants. Direct persecution for consumption still represents a threat with around 20,000 birds taken annually in Northern Peru (P. Majluf in litt. 2007).

Climatic fluctuations associated with El Niño Southern Oscillation (ENSO) also threaten the species. The 1982-83 El Niño caused total reproductive failure and the death of an estimated 1.7 million adult birds in study sites on the Peruvian coast, resulting in a sharper population decline than any of the other studied species (Tovar and Guillén 1987). Communal diving behaviour and the need to exploit large water columns simultaneously may explain why the impacts of El Niño are particularly severe for this species (Weimerskirch et al. 2014). ENSO is a naturally occurring phenomenon and population recovery following previous declines suggest the species has a certain capacity to cope with periodical population crashes (Orta et al. 2018). However, the frequency of ENSO events is expected to increase in concord with future climate change (Timmermann et al. 1999) and adverse climatic conditions operating in synergy with an intensified industrial fishery and compromised food availability could exhaust the species’ adaptive capacity.

Extensive guano mining in the 19th century caused severe population declines through high levels of constant disturbance, habitat conversion and direct exploitation (Orta et al. 2018). Unrestrained guano extraction on breeding islands displaced large numbers of birds and caused the loss of entire colonies. Exploitation of guano is still ongoing, but at a much smaller scale and within regulatory frameworks (Duffy 2000).

Conservation actions

Conservation Actions Underway

Several breeding colonies lie within managed guano reserves or in Marine Protected Areas. Education and awareness on the importance of the conservation of this species has helped raise its local profile. 

Conservation Actions Proposed

Development of a standardised methodology to estimate the population size throughout the breeding range. Evaluate the impact of anchovy fishery on foraging behaviour, breeding seasonality and population dynamics. Evaluate the human consumption of the species in Peru and Chile. Protect important colonies and regulate, or if necessary halt, exploitation. 


76 cm . Upperparts black, with blueish tinge to neck and head, white neck, chest, belly and undertail. Deep red skin around eyes and base of the bill is pink. Feet are also pink (Koepcke 1964). Similar Species: Within its range could be confused with Red-legged Cormorant, but latter is grey not black and has distinctive white neck patch.


Text account compilers
Symes, A., Benstead, P., Lascelles, B., Calvert, R., Martin, R., Fjagesund, T., Miller, E., Moreno, R., Sharpe, C.J.

Roca, M., Frere, E., Majluf, P., Barbraud, C., Engblom, G.

Recommended citation
BirdLife International (2022) Species factsheet: Leucocarbo bougainvilliorum. Downloaded from http://www.birdlife.org on 29/11/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 29/11/2022.