Jacqueline M. Gaudioso-Levita

USGS2024

Divergent trends in distribution and abundance of landbirds in low and high elevation habitats of the Kaʻū Rainforest

Federal, state, and non-governmental partners resurveyed landbirds in the Kaʻū Rainforest on the Island of Hawai‘i in 2019. Point-transect distance sampling was conducted in Hawaiʻi Volcanoes National Park, Kaʻū Forest Reserve, Kapāpala Forest Reserve, and Kapāpala Cooperative Game Management Area. This is the first comprehensive survey of the region since 2008. Through a collaborative effort, monitoring transects were consolidated to provide a consistent, repeatable sampling frame for future surveys. We estimated landbird distribution, density, and abundance for eight surveys since 1976. Changes in species-specific densities were assessed using a log-linear regression to determine trends of the six most recent surveys since 2002. Trends were assessed in three strata: low elevation (<1,500 m), high elevation (≥1,500 m), and total survey area.

Hawaii↗

USGS2017

Biogeographical variation of plumage coloration in the sexually dichromatic Hawai‘i ‘Amakihi (Chlorodrepanis virens)

Plumage coloration in birds can be of major importance to mate selection, social signaling, or predator avoidance. Variations in plumage coloration related to sex, age class, or seasons have been widely studied, but the effect of other factors such as climate is less known. In this study, we examine how carotenoid-based plumage coloration and sexual dichromatism of the Hawai‘i ‘Amakihi ( Chlorodrepanis virens ) varies with rainfall and temperature on Hawai‘i Island. We also examined whether Hawai‘i ‘Amakihi plumage coloration patterns follow Gloger’s rule, which states that animals in wetter climates have darker coloration. Hawai‘i ‘Amakihi were mist-netted and banded at 12 sites representing six major climatic zones on Hawai‘i Island. Feather samples were collected from two body regions: the breast and rump. Using spectrophotometry, we recorded coloration using measures of hue, saturation, and brightness. We conducted sex determination by polymerase chain reaction to confirm the sex of birds sampled. We found that the plumage coloration of Hawai‘i ‘Amakihi varied with both temperature and rainfall. ‘Amakihi plumage’s brightness showed a quadratic relationship with rainfall, contrary to Gloger’s rule, and decreased with temperature. Saturation depended on the interaction between temperature and rainfall. Increases in rainfall also increased saturation in warm areas, while they reduced saturation when the temperature was low. Finally, we found chromatic differences among sexes, but sexual dichromatism was not affected by the climatic conditions. This study provides evidence that rainfall and temperature play an important role in determining the plumage traits of Hawai‘i ‘Amakihi.

Journal of Ornithology↗

USGS2016

Changes in the prevalence of avian disease and mosquito vectors at Hakalau Forest National Wildlife Refuge: a 14-year perspective and assessment of future risk

Throughout the main Hawaiian Islands, introduced mosquito-borne disease has had, and continues to have, a profound impact on the distributions and abundance of native Hawaiian forest birds. Populations of remaining native forest birds are largely restricted to high elevation forests where mean temperatures are marginal for vector and parasite development and limited availability of larval mosquito habitat constrains mosquito populations and disease transmission. Hakalau Forest National Wildlife Refuge (HFNWR) was established for the preservation of endemic avifauna in 1985. Since its creation, native bird communities there have remained intact and most species populations are stable or increasing. However, avian malaria had been detected at HFNWR in the past and, in light of documented climate change, new concerns have been raised regarding the long-term fate of the refuge’s forest birds. To examine the possible changes in avian malaria transmission at HFNWR we sampled forest birds for blood parasites, trapped adult mosquitoes and surveyed larval mosquito habitat at three sites during 2012 and compared our results with similar data collected between 1998 and 1999. We tested blood samples by polymerase chain reaction (PCR), immunoblotting, and microscopy to determine prevalence of acute and chronic infection and used attractive gravid traps to sample the vector mosquito Culex quinquefasciatus. Our study documented spatial trends and temporal changes in the prevalence of avian malaria, mosquito presence, larval mosquito habitat and feral pig activity at HFNWR. We found evidence of local transmission in high elevation forests, a general pattern of increasing prevalence at lower elevations and along a South to North gradient and a two-fold decrease in the prevalence of avian malaria in the intervening 14 years. Despite considerable effort, we were unable to detect larval C. quinquefasciatus and captured only one adult indicating that the vector of avian malaria has a very limited presence at HFNWR. We did, however, document the establishment of another invasive mosquito, Aedes japonicus japonicus , and its occurrence in tree fern cavities and rock pools as larval habitat in the lower forests of HFNWR. We suggest that interspecific competition by A. j. japonicus and predation by a suite of native predators may provide biotic resistance to the establishment of permanent C. quinquefasciatus populations. While current predictions of climate change in the Hawaiian Islands include a gradual warming and enhanced transmission by mid-century, the current cooling trend recorded at high elevation HFNWR illustrates the importance of monitoring to document fine scale temporal and site specific changes in prevalence. Long term changes in precipitation may have a more profound effect on local transmission of malaria than temperature and we may have already seen some potential impacts of an extended drought at HFNWR with a decrease in feral pig activity and pig associated larval mosquito habitat and increases in stream-associated larval mosquito habitat.

Hawaii↗