Sooty Shearwater (Puffinus griseus) on Guafo Island: the largest seabird colony in the world?

Abstract

Sooty Shearwater (Puffinus griseus) is the most common Procellariiform seabird along the south-eastern South American coast. In recent years the wintering population off California has declined noticeably. This decline has been confirmed on the breeding grounds in New Zealand. In Chile, knowledge of the population is limited. Investigations on Isla Guafo were carried out during two seasons (03/04 and 04/05), beginning an ongoing monitoring and evaluation of the breeding population of this species in southern South America. On Isla Guafo we estimate a population of about 4 million birds that nest above 150 m above sea level (m.a.s.l.) under a forest without understory. Sooty Shearwaters on Isla Guafo prefer north and western slopes that we hypothesise protect them from the predominantly southerly winds. Population of the species from New Zealand and Australia are compared with the Isla Guafo population and the state of its conservation is discussed.

Estimating regional population size and annual harvest intensity of the sooty shearwater in New Zealand

“…aside from the few unpublished reports and personal observations, lawton et al (2006) estimate the Diego Ramirez archipelago contains "several thousand pairs" and clark et al (1984) presumed the species was nesting on a few other islands in the area. Despite this paucity of data, Reyes-arriagada et al (2007) suggest that the South american population may be larger than that of New Zealand. without further detailed information it is impossible evaluate this hypothesis.…”

“…in a global perspective this means that the australian population is relatively trivial. The South american population is relatively unknown, even though Reyes-arriagada et al (2007) recently published a population estimate for the island of guafo, located off the west coast of chile. They estimated that this comparatively large island (30 000 ha) supported 3.98 million (±3.87 million, 95% ci) breeding pairs.…”

“…Second, they estimated occupancy by monitoring toothpicks set in burrow entrances, a method which has been found to be an unreliable and seasonally variable indicator of occupancy (hamilton 1998;Scott et al 2008). Third, clark et al (1984) previously estimated the population on guafo to be just 200 000 individuals, two orders of magnitude less than the figure reached by Reyes-arriagada et al (2007). Furthermore, Reyesarriagada et al (2007) found little information on other South american colonies.…”

Improving the accuracy of population size estimates for burrow‐nesting seabirds

“…Many animals, including seabirds, build nests, which provide a temporally and spatially stable index of their abundance (Rayner et al 2007). The most common technique to estimate the number of breeding seabirds in large populations has been to predict an appropriate time to survey active nests, assume that each active nest represents a breeding pair, estimate density from a representative sample of the population, and apply that density to measured areas of occupancy (Lawton et al 2006, Priddel et al 2006, Rayner et al 2007, Reyes-Arriagada et al 2007, Barbraud et al 2009). While allowing a general population size to be interpreted, this technique makes numerous assumptions that are in many cases untested and may have a large and variable influence on estimates between years.…”

Variation in abundance and harvest of sooty shearwaters (Puffinus griseus) by Rakiura Maori on Putauhinu Island, New Zealand

“…1175-8821 (Online); 0301-4223 (Print)/09/3603-0275 © The Royal Society of New Zealand 2009 Variation in abundance and harvest of sooty shearwaters (Puffinus griseus) by Rakiura Maori on Putauhinu Island, New Zealand INTRODUCTION Rakiura Maori harvest tïtï (sooty shearwater chicks; Puffinus griseus) on the Tïtï Islands around Stewart Island in southern New Zealand, in what is one of the few remaining large-scale cultural harvests permitted in the country (Wilson 1979). This species is an abundant, medium-sized petrel that nests in burrows on islands around southern New Zealand, South America and Tasmania (Warham & Wilson 1982;Reyes-Arriagada et al 2007). After breeding during the austral summer, most of the population migrate to the North Pacific during winter (Shaffer et al 2006).…”