Breeding distribution and abundance of seabirds on islands off north-central Chile

Alejandro Simeone,Macarena Contreras,Tamara Pince,Ursula Ellenberg,Stefan Garthe,Mariano Bernal,Roberto Villablanca,Felipe Sepúlveda,Julieta Muñoz,Guillermo Lara-Jorquera

doi:10.4067/s0716-078x2003000200016

Abstract

Between 1999 and 2003 we collected information on the breeding distribution and abundance of 12 seabird species occurring on nine islands off the coasts of north and central Chile (27°-33°S). The Peruvian booby Sula variegata was the most abundant seabird with a breeding population of ca. 18,000 pairs concentrated in two islands, followed by the Humboldt penguin Spheniscus humboldti with ca. 9,000 pairs, the largest colony being at Chanaral Island with ca. 7,000 pairs. Kelp gulls Larus dominicanus bred at all the surveyed sites in colonies of variable size, ranging from 40 to 2,000 pairs. Peruvian diving-petrels Pelecanoides garnotii and Peruvian pelicans Pelecanus occidentalis bred at restricted sites, but generally in large colonies. Magellanic penguins Spheniscus magellanicus, wedge-rumped storm-petrels Oceanodroma tethys, Neotropical cormorants Hypoleucos brasiliensis, guanay cormorants Leucocarbo bougainvillii, red-legged cormorants Stictocarbo gairmardi, band-tailed gulls Larus belcheri and Inca terns Larosterna inca nested at few sites forming small colonies (from a few to 150 pairs). Two new breeding sites are reported for the Peruvian diving-petrel and nesting of the wedge-rumped storm-petrel is confirmed on the Chilean coast for the first time. Despite protective status, most of the islands showed human disturbance, derived mainly from guano harvesting, egging and tourism. On at least five of these islands we were able to confirm introduced mammals including rats, rabbits and cats. These factors are likely to be detrimental to seabirds and thus demand detailed assessment. Further comprehensive ornithological surveys in other areas are needed so as to improve the scarce knowledge that we currently have on the seabird populations along the Chilean coast

Highlights

Seabirds are key components of the pelagic marine ecosystem and appropriate monitoring of their populations can provide, in addition to their obvious important contribution to their conservation per se, useful information on several aspects of the marine environment, including the distribution of their fish prey, pollution and the onset of oceanographic anomalies (Monaghan 1996, Furness & Camphuysen 1997).The continental Chilean coast extends over 4,200 km from the subtropical waters at 18° S to the cold temperate seas at 56° S, a territory within which over 50 seabird species breed on numerous islands and coastal localities (Schlatter 1984)
The continental Chilean coast extends over 4,200 km from the subtropical waters at 18° S to the cold temperate seas at 56° S, a territory within which over 50 seabird species breed on numerous islands and coastal localities (Schlatter 1984)
Despite the considerable range of seabird habitat and large number of seabird species along the Chilean coast (109 according to Schlatter & Simeone 1999), little is known of their reproductive distribution and abundance

Summary

Introduction

The continental Chilean coast extends over 4,200 km from the subtropical waters at 18° S to the cold temperate seas at 56° S, a territory within which over 50 seabird species breed on numerous islands and coastal localities (Schlatter 1984). Most of this coastline is influenced by the northward flowing Humboldt current, coastal upwelling processes and the periodic occurrence of El Niño events (Camus 2001), all factors that strongly influence the composition and abundance of the seabird assemblage and contribute to its uniqueness, including a large number of endemic species (Murphy 1936, Schlatter & Simeone 1999). Except for few recent studies (e.g., Simeone & Schlatter 1998, Guicking et al 1999, Vilina & Gazitúa 1999, Simeone & Bernal 2000), data on reproductive abundance and location of seabird colonies in Chile are scarce and found mostly dispersed in the literature or accessible only through personal communications of ornithologists

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Conclusion