Declining population trends of Hawaiian Petrel and Newell's Shearwater on the island of Kaua'i, Hawaii, USA

The island of Kaua'i, Hawaii, USA, holds a large breeding populations of the endangered Hawaiian Petrel (Pterodroma sandwichensis) and a majority of the world population of the threatened Newell's Shearwater (Puffinus newelli). We evaluated island-wide population trends of both species. Fo...

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Bibliographic Details
Published in:The Condor (Los Angeles, Calif.) Calif.), 2017-08, Vol.119 (3), p.405
Main Authors: Raine, André F, Holmes, Nick D, Travers, Marc, Cooper, Brian A, Day, Robert H
Format: Article
Language:English
Subjects:
Animal populations
Animal reproduction
Attraction
Birds
Conservation
Datasets
Endangered populations
Hurricanes
Ornithology
Population decline
Predators
Radar
Radar data
Species
Trends
World population
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Summary:The island of Kaua'i, Hawaii, USA, holds a large breeding populations of the endangered Hawaiian Petrel (Pterodroma sandwichensis) and a majority of the world population of the threatened Newell's Shearwater (Puffinus newelli). We evaluated island-wide population trends of both species. For Newell's Shearwaters, we considered radar counts at 13 sites between 1993 and 2013 and annual island-wide tallies of fledglings retrieved after being grounded by light attraction in 1979-2015 (Save Our Shearwaters [SOS] program). For Hawaiian Petrels, we considered radar counts alone. Radar data indicated a 78% decline overall in numbers of Hawaiian Petrels (at an average rate of ~6% per year) and a 94% decline overall in numbers of Newell's Shearwaters (at an average rate of ~13% per year) during the survey period. Most (92%) radar sites showed significant declines of Newell's Shearwaters across the entire survey period, as did 62% of sites for Hawaiian Petrels. The SOS recovery effort collected 30,522 Newell's Shearwater fledglings between 1979 and 2015. When we compared this dataset in pre- and post-Hurricane Iniki (September 1992) periods, we found a significant downward trend after Hurricane Iniki, similar to the trend seen in the radar data. The large-scale declines found in this study are not surprising, considering the significant threats facing both species on Kaua'i, which include powerline collisions, light attraction, introduced predators, and habitat modification -- threats which were potentially exacerbated after Hurricane Iniki. Improved conservation initiatives and an increased understanding of the various threats facing the 2 species are key to reversing these declines.
ISSN:2732-4621
DOI:10.1650/CONDOR-16-223.1