The regent honeyeater is Australia’s most threatened songbird. Once common throughout the south-east (including suburban Sydney and Melbourne), the population has crashed since the 1960’s due to extensive land clearing. It is now on the verge of extinction, listed as critically endangered under national and international legislation. Best available data suggest that fewer than 400 individuals remain and population decline is ongoing.
Regent honeyeaters exploit flowering events to feed on a select number of Eucalyptus species, with a strong preference for highly threatened Yellow box Eucalytpus melliodora and Mugga Ironbark Eucalyptus sideroxylon. Current knowledge suggests their movement and settlement patterns reflect high spatiotemporal variability in the timing and intensity of flowering events in their preferred food trees. The birds nest during the Austral spring/summer and can form small breeding aggregations where habitat conditions are suitable. They are territorial and aggressively defend their nesting area.
WHY IT’S DIFFICULT
Regent honeyeaters are highly mobile and extremely elusive. With its small population size (<400) and massive range (>600,000 km2) finding this species, let alone studying it, presents a world of challenges. There are very few places where the bird can be reliably detected between and within years. This has severely limited attempts to understand why the regent honeyeater has declined so severely and rapidly, particularly among other co-occurring nectarivore species that persist at high abundances in similar environments.
WHAT WE’RE DOING
We are currently undertaking national-scale monitoring throughout the species’ range, in order to substantially improve our knowledge of the regent honeyeater’s habitat requirements, nesting success rates and causes of nesting failure, as well as their movement patterns and social ecology. Our primary project aims are:
1) Collect ecological evidence to enhance and direct current and future conservation actions (such as habitat restoration, land protection and captive release) for regent honeyeaters;
2) Track the flower and nectar phenology of dominant Eucalyptus feed trees across the species’ range to improve our understanding of regent honeyeater movement, habitat selection, competition and social dynamics;
3) Devise innovative ways to prevent the extinction of wild regent honeyeaters that explicitly account for the species’ unusual ecological attributes and requirements;
4) Undertake cutting-edge genetic analyses to understand and manage the impacts of rapid population decline on the genetic make-up of the regent honeyeater population;
5) Determine how the population decline could affect the song repertoire of the regent honeyeater, particularly individual males.
Despite it’s iconic status and the urgent need for conservation advice, no standardised range-wide monitoring protocol exists for the regent honeyeater. To date, our entire understanding of population size and trajectory is drawn from haphazard landscape-scale surveys and, crucially, incidental sightings from members of the concerned public.
Strategic and standardised monitoring of the regent honeyeater population across its full extent of occurrence is vital for (i) deriving robust population estimates, (ii) identifying critical breeding and foraging habitat, and (iii) directing effective conservation action. Importantly, a holistic national-scale approach to monitoring allows for comparisons between and among known breeding landscapes, across space and through time. Such information is currently unavailable, but will be essential for (i) understanding interactive and emerging threats to the species’ survival, (ii) tracking variation in the abundance and availability of critical foraging and nesting resources, and (iii) forecasting the impacts of climate change on regent honeyeater distributions and population persistence.
Further to a holistic approach, monitoring for this rare and highly mobile bird must be targeted. A monitoring program tailored specifically to the species’ ecology is crucial for maximising return (i.e. sightings) on investment (i.e. search effort). With fewer than 400 birds spread across an area the size of France, strategic site placement is key. In turn, we have gone to massive efforts to gather the most up-to-date knowledge on regent honeyeater ecology and used all available sightings data to construct highly sophisticated species distribution models to design our new national regent honeyeater monitoring program.
Using these models, we have identified areas of priority habitat for the regent honeyeater based on predictions of high suitability across multiple years and varying climatic conditions. We have established over 1,000 sites in these priority areas, including all regions defined as “key breeding areas” in the updated Regent Honeyeater Recovery Plan. Surveys are repeated five-minute point-counts to record regent honeyeater presence-absence and abundance at each site. Surveys take place during the breeding season when we record the distribution and abundance of the regent honeyeater population in both breeding and foraging habitat across their known range. During each survey, we also record all other birds detected and score flowering of potential food trees on a scale of 0 to 4, where 0 = no flower, 1 = light, 2 = moderate, 3 = heavy and 4 = very heavy. This provides a broad-scale measure of food abundance during the breeding season.
Local - Landscape scale
We have developed a monitoring strategy that is successfully locating birds at multiple scales. Our surveys are providing a reliable guide to the location of nesting events. To date, we have monitored 49 nests, from which we will (i) quantify rates of nesting success, (ii) identify the causes of nesting failure, and (iii) elucidate the importance of the nectar resource to nesting birds. This knowledge will be used to inform management actions to enhance the breeding success of wild regent honeyeaters.
For the 2016/7 season, we have up-scaled our monitoring efforts in the Capertee Valley, search and monitoring birds at the landscape-scale. These data will enable us to study habitat associations between regent honeyeaters and its competitors (including the hyper-aggressive noisy miner), and effectively guide immediate and future management of competitor populations at critical regent honeyeater breeding locations. These monitoring data will also be used to examine landscape-scale changes in flowering phenology to determine how nectarivores differ in their distributions, and their dependence on nectar, through time.
To date, we have colour-banded 42 regent honeyeaters, providing us with very useful movement and survival data. DNA samples have been obtained from all banded birds and are currently being processed in the ANU laboratories to form a key component of a population genomics study. Regent honeyeaters have a song repertoire that is highly variable between individuals. Hence, we have recorded the song of every individually-identifiable male regent honeyeater to examine the implications of song variation for fitness. We have also commenced satellite tagging of noisy friarbirds to investigate their role as a potential surrogate for macro-scale nectarivore dispersal patterns.