Evaluating abundance and trends in a Hawaiian avian community using state-space analysis

Bird Conservation International
By: , and 

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Abstract

Estimating population abundances and patterns of change over time are important in both ecology and conservation. Trend assessment typically entails fitting a regression to a time series of abundances to estimate population trajectory. However, changes in abundance estimates from year-to-year across time are due to both true variation in population size (process variation) and variation due to imperfect sampling and model fit. State-space models are a relatively new method that can be used to partition the error components and quantify trends based only on process variation. We compare a state-space modelling approach with a more traditional linear regression approach to assess trends in uncorrected raw counts and detection-corrected abundance estimates of forest birds at Hakalau Forest National Wildlife Refuge, Hawai‘i. Most species demonstrated similar trends using either method. In general, evidence for trends using state-space models was less strong than for linear regression, as measured by estimates of precision. However, while the state-space models may sacrifice precision, the expectation is that these estimates provide a better representation of the real world biological processes of interest because they are partitioning process variation (environmental and demographic variation) and observation variation (sampling and model variation). The state-space approach also provides annual estimates of abundance which can be used by managers to set conservation strategies, and can be linked to factors that vary by year, such as climate, to better understand processes that drive population trends.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Evaluating abundance and trends in a Hawaiian avian community using state-space analysis
Series title Bird Conservation International
DOI 10.1017/S0959270915000088
Volume 26
Issue 2
Year Published 2016
Language English
Publisher Cambridge University Press
Publisher location Cambridge
Contributing office(s) Pacific Island Ecosystems Research Center
Description 18 p.
First page 225
Last page 242
Country United States
State Hawai'i
Other Geospatial Hakalau Forest National Wildlife Refuge
Online Only (Y/N) N
Additional Online Files (Y/N) N