Grasswrens, glorious grasswrens

Guest bloggers
Published 25 Oct 2019 
by Aline Gibson Vega 
about  Hamelin Station Reserve  
Female western grasswren, showing off her bright colour bands. Notice her rufous flanks. Photo: Aline Gibson Vega.<br/> Female western grasswren, showing off her bright colour bands. Notice her rufous flanks. Photo: Aline Gibson Vega.
Once colourbanded, each individual is identifiable in the wild. Photo: Aline Gibson Vega.<br/> Once colourbanded, each individual is identifiable in the wild. Photo: Aline Gibson Vega.
Western grasswren habitat. Photo: Aline Gibson Vega.<br/> Western grasswren habitat. Photo: Aline Gibson Vega.
Juvenile male western grasswren, about to be processed. Photo: Richard Winterton.<br/> Juvenile male western grasswren, about to be processed. Photo: Richard Winterton.

Hamelin Station Reserve is brimming with birdlife. But if you're not paying close attention, there's one species that can easily be missed – the Western Grasswren. Grasswrens are very poorly understood compared to their glamorous cousins, the fairywrens.

It isn’t clear why the Western Grasswren had such a dramatic population decline. Thought to be once found throughout much of WA, this ground-dwelling species is now restricted Peron Peninsula, Hamelin Station and Carbla Station.

My PhD project, a collaboration between the University of Western Australia, Bush Heritage Australia and the Department of Biodiversity, Conservation and Attractions, will focus on understanding the population genetics, breeding biology and behaviour of this cryptic species. This winter was my first field season at Hamelin Station Reserve, and I was very excited to get to know my study species.

The first priority of this field season was to have some grasswrens banded with unique combinations of coloured leg bands. By doing so, individuals are identifiable from a distance (without re-capture). Individual tagging is the only way to learn about how long individuals survive, and individual movements, and will allow me to keep track of the group’s movements, breeding attempts and dispersal over the next three years.

Capturing grasswrens to band them was quite tricky as the grasswrens must be persuaded to approach the net using a combination of gentle herding and playback song. Once caught, we put colour bands on their legs, took morphological measurements and sampled a small quantity of blood. These individuals are likely to be caught only once in their lifetime, so it’s important to take down key information while the opportunity is there.

With my groups now identifiable, the second priority was to find nests to monitor their breeding attempts.

Grasswrens, by nature, are sneaky. Sneaky grasswrens equates to sneaky nest placement! Finding nests was by far the hardest part of the project so far. We found the nests by following females and strategically checking vegetation. Nests were checked every couple of days to document their progress.

These birds are quite unusual in many aspects. The female is slightly more decorated than the male – she has a small rufous patch on her flank. Their behaviour is also very mammal-like, with the grasswrens bounding from shrub to shrub and seldom seen flying. We’ve found them in a range of habitats, but they all have common elements – tall perching points, thick shrubs and a semi-open landscape between the shrubs.

There's still a lot we don’t know about them, but with every passing day I’m learning more about this elusive species.

So why bother going through the effort of understanding this cryptic bird? Well, the Western Grasswren is one of the species planned to be translocated to Dirk Hartog Island as part of the Return to 1616 project (which aims to return the vegetation and habitats of the Island to what Dirk would have seen when he found them in 1616).

Grasswrens were once found on the island but are now locally extinct there. To create a robust translocation strategy, key pillars of information are required about a species – and there's not enough information at the moment for the Western Grasswren. The data collected through my PhD will directly inform the management of this species, both within Hamelin Station Reserve and on Dirk Hartog Island in the future.

Once colourbanded, each individual is identifiable in the wild. Photo: Aline Gibson Vega.<br/> Once colourbanded, each individual is identifiable in the wild. Photo: Aline Gibson Vega.
Western grasswren habitat. Photo: Aline Gibson Vega.<br/> Western grasswren habitat. Photo: Aline Gibson Vega.
Juvenile male western grasswren, about to be processed. Photo: Richard Winterton.<br/> Juvenile male western grasswren, about to be processed. Photo: Richard Winterton.