Long-term monitoring of endangered Laysan ducks: Index validation and population estimates 1998–2012

Journal of Fish and Wildlife Management
By: , and 

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Abstract

Monitoring endangered wildlife is essential to assessing management or recovery objectives and learning about population status. We tested assumptions of a population index for endangered Laysan duck (or teal; Anas laysanensis) monitored using mark–resight methods on Laysan Island, Hawai’i. We marked 723 Laysan ducks between 1998 and 2009 and identified seasonal surveys through 2012 that met accuracy and precision criteria for estimating population abundance. Our results provide a 15-y time series of seasonal population estimates at Laysan Island. We found differences in detection among seasons and how observed counts related to population estimates. The highest counts and the strongest relationship between count and population estimates occurred in autumn (September–November). The best autumn surveys yielded population abundance estimates that ranged from 674 (95% CI = 619–730) in 2003 to 339 (95% CI = 265–413) in 2012. A population decline of 42% was observed between 2010 and 2012 after consecutive storms and Japan’s To¯hoku earthquake-generated tsunami in 2011. Our results show positive correlations between the seasonal maximum counts and population estimates from the same date, and support the use of standardized bimonthly counts of unmarked birds as a valid index to monitor trends among years within a season at Laysan Island.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Long-term monitoring of endangered Laysan ducks: Index validation and population estimates 1998–2012
Series title Journal of Fish and Wildlife Management
DOI 10.3996/032014-JFWM-017
Volume 6
Issue 1
Year Published 2015
Language English
Publisher U.S. Fish and Wildlife Service
Publisher location Washington, D.C.
Contributing office(s) Pacific Island Ecosystems Research Center
Description 10 p.
First page 92
Last page 101
Country United States
State Hawai’i
Online Only (Y/N) N
Additional Online Files (Y/N) N