Palila abundance and trend

Abstract

The Palila (Loxioides bailleui) is an endangered, seed-eating, finch-billed honeycreeper found only on Hawai`i Island. Once occurring on the islands of Kaua`i and O`ahu and Mauna Loa and Hualālai volcanoes of Hawai`i, Palila are now found only in subalpine, dry-forest habitats on Mauna Kea (Banko et al. 2002). Previous analyses showed that Palila numbers fluctuated throughout the 1980s and 1990s but declined rapidly and steadily since 2003 (Jacobi et al. 1996, Leonard et al. 2008, Banko et al. 2009, Gorresen et al. 2009, Banko et al. in press).

The aim of this report is to update abundance estimates for the Palila based on the 2012 surveys. We assess Palila trends over two periods: 1) the long-term trend during 1998–2012 and 2) the short-term trajectory between 2003 and 2012. The first period evaluates the population trend for the entire time series since additional transects were established (Johnson et al. 2006). These additional transects were established to produce a more precise population estimate and provide more complete coverage of the Palila range. The initial year for short-term trajectory was chosen subjectively to coincide with the recent decline in the Palila population. Additionally, stations in the core Palila habitat were surveyed on two occasions in 2012, thus allowing us to address the question of how repeat samples improve estimate precision.