By Jack Stodart
The regent honeyeater (Anthochaera phrygia) is a critically endangered bird endemic to eastern Australia. Over the last few decades, there has been a dramatic decline in the populations of the regent honeyeater. Two of the most significant threats to the species are habitat loss and attacks from other birds, particularly noisy miners (Manorina melanocephala).
ANU PhD student Ross Crates is investigating these two threats and working on solutions. Over three days in September 2018, I assisted Ross with his research and learned how we might save the regent honeyeater.
Ross Crates and fellow student Courtney Webber identify birds by their calls.
Tackling noisy miners
Adjacent to the Goulburn River National Park in eastern NSW is a biodiversity offset site purchased to offset a nearby coal mine. In one section of the property, noisy miners have been culled, and at another section they have been left. We surveyed bird species in the control and treatment sections to see whether culling noisy miners was leading to greater abundance and diversity of other bird species.
So far, the culling appears to have been highly successful, both for the regent honeyeater and several other native songbirds. Ross has also found that after culling, the noisy miners are slow to return, providing longer protection for other birds.
Restoring habitat is unfortunately not as easy. Regent honeyeaters require a few important habitat features.
Yellow box blossom (Eucalyptus melliodora) is a critical food source, providing long flowering periods and ample nectar. Mugga ironbark has been shown to be correlated with higher habitat selection by regent honeyeaters. The blossom of various species of mistletoe also supply nectar. However, some species of mistletoe have been dying off to some degree, particularly Amyema cambagei, which grows on river she-oak (Casuarina cunninghamiana subsp. cunninghamiana). Regent honeyeaters also often breed and nest in river she-oak along river banks.
Left: Bare downward-pointing branches of dead mistletoe on a river she-oak. Right: Natural river she-oak regeneration in the Goulburn River.
This offset site, previously a grazing farm, is somewhat typical of the region. Hilltops have remained densely wooded, but flat areas around the river have been highly cleared. Unfortunately, the river flats are where most of the yellow box and mugga ironbark occur.
The goal is to revegetate these flats with yellow box and other species that would have naturally occurred there, and that provide suitable habitat for regent honeyeaters as well as a host of other threatened native birds. Fortunately as well, we saw that there has naturally been strong recruitment of river she-oak along the river banks in the offset property.
Left: Tree plantings at the Capertee Valley National Park. Right: River flats at the offset property that Ross hopes can be replanted.
The good news is that if these areas can be revegetated, the noisy miners are not likely to return. Noisy miners are ‘edge specialists’, adapted to living on the boundaries of wooded areas or along open river banks, near open scrub or grassland. By reducing the area of ‘edge’ woodland, we may also be able reduce competition and attacks from noisy miners.
The even better news is that by protecting the regent honeyeater, we are also protecting threatened tree species and myriad other native birds. While we didn’t spot any regent honeyeaters this time, we did see speckled warblers (Chthonicola sagittata), brown treecreepers (Climacteris picumnus victoriae), and even a spotted harrier (Circus assimilis), all of which stand to benefit from Ross’ research.
All photos: Jack Stodart