Reproduction and population levels of Peruvian Guano Birds, 1980 to 1986

Abstract

The three species of guano birds, guanay cormorant (Phalacrocorax bougainvillii), Peruvian booby (Sula variegate), and Peruvian pelican (Pelecanus occidentalis thagus), depend mainly on the Peruvian anchovy (Engraulis ringens) for sustenance. A naturally occurring limitation on the population size of these birds is the oceanographic phenomenon known as “El Niño”. The industrialization of the anchovy fishery during the 1960s and 1970s has also affected seabird populations: The annual extraction of huge volumes offish has decreased the availability of food for the guano birds, causing large population fluctuations and considerable changes in the relative abundance of the birds. Because of its great intensity and duration, the 1982–1983 El Niño caused high avian mortality, depressing populations to levels from which they have not yet recovered.

Environmental change in the eastern tropical Pacific Ocean: review of ENSO and decadal variability

“…Blue-footed booby reproductive attempts failed and breeding colonies were abandoned during the 1986-87 El Niño, apparently in response to reduced availability of sardines, but several other species were not affected (Anderson 1989). Guanoproducing seabirds in coastal Peru have consistently experienced adult mortality and decreased reproductive success during El Niño events; these are shortterm population effects, resulting from reduced availability of anchoveta (Tovar et al 1987, Crawford & Jahncke 1999. All 15 species of seabirds nesting on the Galapagos Islands stopped breeding or experienced reduced reproductive success during El Niño 1982-83, but resumed breeding the following year (Valle et al 1987).…”

Oceanographic and climatic factors influencing breeding and colony attendance patterns of Humboldt penguins Spheniscus humboldti in central Chile

“…This causes massive nest desertions, increased adult mortality, and large-scale movements in several seabird species (Vogt 1942, Tovar & Guillén 1987, Valle et al 1987. El Niño also causes anomalously heavy rainfall (Rasmusson & Wallace 1983).…”

“…Alterations in these breeding and attendance patterns occur mainly during El Niño events, when anomalously heavy rainfall and food shortage interrupt breeding and force birds to abandon their colonies (Hays 1986, Paredes & Zavalaga 1998 in search of more productive areas at sea (Culik et al 2000). Reductions in breeding performance, and changes in distribution and population levels of seabirds due to El Niño are particularly strong along the coasts of Ecuador and Perú (Barber & Chávez 1983, Tovar & Guillén 1987, Valle et al 1987, Duffy 1990.…”

“…Alterations in these breeding and attendance patterns occur mainly during El Niño events, when anomalously heavy rainfall and food shortage interrupt breeding and force birds to abandon their colonies (Hays 1986, Paredes & Zavalaga 1998 in search of more productive areas at sea (Culik et al 2000). Reductions in breeding performance, and changes in distribution and population levels of seabirds due to El Niño are particularly strong along the coasts of Ecuador and Perú (Barber & Chávez 1983, Tovar & Guillén 1987, Valle et al 1987, Duffy 1990.In central Chile between 32°and 36°S, where ca. 20% of the total Humboldt penguin population is to be found (Ellis et al 1998), upwelling is relatively lighter and seasonal compared to that in Perú (Wooster & Sievers 1970, Johnson et al 1980, Ahumada et al 1983, rainfall is much higher and concentrated in winter (FAO 1985), and the effects of El Niño on seabird populations are comparatively less severe (Duffy 1990).…”

“The Most Valuable Birds in the World”: International Conservation Science and the Revival of Peru's Guano Industry, 1909–1965

“…Fortunately, these wrong-headed experiments failed: These chemicals are now known to cause egg-thinning, breeding failure, and direct poisoning in the very birds CAG was trying to protect. 64 …”