Ecology and Conservation of the Regent Honeyeater

Abstract

In the age of the Anthropocene, avian diversity loss is occurring at an unprecendented rate. Australia is not immune to the Global extinction crisis, given pervasive threats from habitat loss, climate change and introduced species. High variability in Australia’s climatic conditions has led many birds to evolve mobile life-histories, presenting unique challenges for their conservation. The nomadic, critically endangered regent honeyeater Anthochaera phrygia has suffered a severe population decline since the mid-19th century. The contemporary population is estimated to consist of 350-500 individuals, distributed across 600,000 km2 of woodland in south-east Australia. The species tracks nectar resources at large spatial scales. Small population size, vast range and irregular movement patterns of the regent honeyeater have hampered understanding of the drivers of ongoing population decline. Lack of ecological data has prevented efforts to implement targeted management actions to conserve the wild population. This thesis aims to obtain contemporary ecological data to inform efforts to prevent extinction of the regent honeyeater. In chapter 2, we develop a monitoring strategy to locate breeding regent honeyeaters using a survey protocol that accounts for their rarity and mobility. Although regent honeyeaters are rare, they are not cryptic. In chapter 3, we review the literature on Allee effects to evaluate, based on life-history traits, the susceptibility of Australia’s critically endangered birds to inverse density dependent population growth. We use the regent honeyeater to show how a lack of empirical evidence of Allee effects need not preclude efforts to account for their existence through precautionary conservation. In chapter 4, we present the contemporary breeding biology of regent honeyeaters. We provide evidence that nest success and productivity have declined over recent decades, nest success is highly spatially variable, predation is the main cause of nest failure and there is a male bias to the adult sex ratio. In chapter 5, we experimentally removed noisy miners, a major competitor and known cause of nesting failure, from a regent honeyeater breeding site. We monitored recolonisation of noisy miners following their removal, the co-occurrence of noisy miners and regent honeyeaters during nesting, and the response of the songbird community to miner removal. We significantly decreased noisy miner abundance at a time and location to benefit breeding regent honeyeaters. Abundance and species richness of the songbird community also increased. In chapter 6, we evaluate the genomic impact of severe population decline in regent honeyeaters. We find very weak population structure in the population prior to its rapid decline, that the population comprises a single conservation unit, and that some genetic diversity loss has occurred over the past 3 decades. In combination, effort and effective sampling can generate crucial population data to inform better conservation of rare and highly mobile species that may otherwise be dismissed as too challenging to study in detail. Show more