Threatened Species Day: Critically Endangered Capricorn Yellow Chat and the Innovative Use of Terrestrial Environmental DNA

• National Threatened Species Day - 7 September

• The Capricorn Yellow Chat (Epthianura crocea macgregori) is listed as Critically Endangered under the Commonwealth Environmental Protection and Biodiversity Conservation Act 1999. 

• Collaboration between EnviroDNA and CQUniversity applied innovative terrestrial eDNA methods to support ongoing research.

The Capricorn Yellow Chat (Epthianura crocea macgregori) is one of Queensland’s rarest birds. This tiny subspecies weighs less than two teaspoons of sugar and despite its bright appearance, it’s a major challenge to spot in the wild due to their elusive habits, small population numbers, and inhospitable habitat. 

This subspecies was thought to be extinct in 1991 but was rediscovered. Today there are only 250 individuals left in isolated regions across Queensland's Capricorn Coast. They are surviving against the myriads of threats of climate change, habitat loss, and invasive species.  

Research is underway to protect the species. Central Queensland University (CQU) is one of the organisations tackling its recovery efforts. They’ve undertaken significant research into population demography, genetics, and behaviour over roughly 20 years.  

Dr Grace Blackburn, a Postdoctoral Research Fellow at CQU, says part of this research was aiming to answer two key questions: “Which species are predating chat nests, and what are chats themselves preying on?” 

Initially, research involved deploying artificial nests to understand predators by classifying marks on predated plasticine eggs as either beak or teeth marks. However, this method only allows for broad taxa level such as mammal vs birds, and many plasticine eggs had no obvious marks. Secondly, camera traps were used to identify species predating nests. 

‘That brought us to eDNA. It allowed us to classify, sometimes to species level, the predators responsible for nest predation on nests without camera traps.’

This collaboration considered how eDNA doesn’t disperse as easily as aquatic environments and requires a tactical sampling strategy. To maximise the chances of accurate detection, an innovative sampling strategy was designed using artificial eggs and nest rinsing, enabling the collection of as much eDNA as possible. 

During the survey, CQU personnel staged nesting sites with a mix of quail and artificial plasticene eggs. Predated nests were then recollected and rinsed. A total of 5 egg swabs and 5 water samples were captured. These methods captured the traces of DNA left behind from saliva or other sources of interaction with the eggs and nest. EnviroDNA analysed samples using vertebrate metabarcoding to assess predation of the Capricorn yellow chat eggs. 

EnviroDNA analysis revealed that 25 taxa were detected, including 6 introduced species and 9 native species. Detections included 8 fish, 1 amphibian, 9 birds, and 7 mammals. Through detection of high DNA reads and using additional ecological validation, we can infer that it was likely brahminy kites, black kites, and red foxes predating on the eggs.  

‘Interestingly, we saw a greater array of predators when using eDNA compared to camera traps,’ says Grace Blackburn. 

‘It was a positive outcome given that it’s possible that some predators are camera-shy and less likely to be captured on camera. Or predators may have been using the cameras as a cue to locate the artificial nests.’ 

Concurrent research undertaken `using eDNA to determine the diet of Capricorn Yellow Chats revealed 26 taxa present in 10 chat scat samples. The genus Odontomyia (soldier flies) was the most detected taxon, with the mosquito species (Culex sitiens) the most detected at the species taxonomic rank. 

Combined, the surveys revealed insights into the bottom-to-top food chain. By expanding survey efforts with creative eDNA techniques, EnviroDNA analysis revealed hidden ecological interactions that would otherwise remain invisible. These insights provide evidence to identify key threats and guide management decisions on the ground. 

‘We'll use these findings to inform management of invasive species in Central Queensland. Since the red fox has been identified as a predator of chat nests, we hope these findings will be used to inform fox control and management in areas used by the Capricorn Yellow Chat.’

This project shows that even the smallest traces of DNA can tell complete stories that can help secure the future of endangered species. EnviroDNA was pleased to collaborate with CQ University and help build another chapter in the story of the Capricorn Yellow Chat.

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