New research demonstrates that lyrebirds transfer more litter and soil than any other animal digging

New research demonstrates that lyrebirds transfer more litter and soil than any other animal digging

What comes to mind when you think of lyrebirds might be the sound of camera clicks, chainsaws and other birds' songs. Although it is remarkable to mimic lyrebirds, it is not the only striking characteristic of this genus.

We record the remarkable changes that lyrebirds make to the ground layer in forests in their role as an ecosystem engineer in research just published.

In ways that depend on other organisms, ecosystem engineers modify the climate. Without the lyrebirds, forests in eastern Australia will be very different areas.

What is an Engineer in the Ecosystem?

In several settings, ecosystem engineers exist. They establish new environments or change existing environments by altering the soil in a way that affects other species, such as plants and fungi.

In North America, a well-known example is the beaver, which uses logs and mud to dam a stream and build a deep pond. In so doing, for many animals, including frogs, herons, fish and aquatic plants, it affects the aquatic ecosystem. Additional examples include bettongs and bandicoots.

The Superb Lyrebird serves as an ecosystem engineer while foraging for food by its displacement of leaf litter and soil. To rake the forest floor, exposing bare soil and mixing and burying debris, when finding invertebrate prey such as worms, centipedes and spiders, Lyrebirds use their strong claws.

We carried out a two-year experiment in Victoria's Central Highlands, with three experimental treatments, to research the role of the lyrebird as an engineer.

Next, a fenced treatment in which lyrebirds have been removed from fenced 3 m wide square plots.

Second, an identical fenced plot, but in which we simulated a three-pronged hand rake foraging of lyrebirds (about the width of the foot of a lyrebird). This imitated the lyrebirds' soil disturbance, but without the birds consuming the invertebrates that lived there.

An unclosed, open plot (of the same size) in which wild lyrebirds were free to forage as they pleased, was the third procedure.

We tracked changes in the litter and soil over a two-year span, and calculated the amount of soil displaced within and outside of these plots.

New research demonstrates that lyrebirds transfer more litter and soil than any other animal digging

Lyrebirds dig up a lot of dirt

On average, wild lyrebird drilling resulted in a whopping 155 tons of litter and soil per hectare displaced in these forests per year.

This is more than any other digging vertebrate, globally, to the best of our understanding.

To put this in perspective, most digging vertebrates around the world displace between 10-20 tons of material per hectare per year, such as pocket gophers, moles, bandicoots and bettongs.

Imagine the load borne by five medium-size 30 ton dump trucks to imagine what 155 tonnes of soil looks like, and this is only for one hectare!

But how much does a lyrebird displace an individual? Thanks to the work of citizen scientists led by the Sherbrooke Lyrebird Research Group, we estimated the density of the lyrebird population at one study location to be approximately one lyrebird per 2.3 hectares of forest.

A single lyrebird will displace approximately 11 litter and soil dump trucks in a single year, based on this calculation, and using our dump truck analogy.

Changes to the ground layer

After two years of exclusion of lyrebirds, leaf litter was nearly three times deeper in the fenced plots than in the unfenced plots. In the fenced plots, soil compaction was even greater.

The soil easily crumbled and the litter layer never fully recovered to a lyrebird-free state before foraging occurred again when lyrebirds foraged.

For centuries, this complex phase of lyrebird disturbance has been going on, forming these forests deeply. Under the influence of lyrebirds, the forest floor may provide new possibilities for species such as centipedes, spiders and worms living in the litter and soil that would not occur in their absence.

Terraced soil where litter has been removed and roots exposed by foraging lyrebirds
Terraced soil where litter has been removed and roots exposed by foraging lyrebirds

An ecosystem ravaged by fire

According to a preliminary report by BirdLife Australia , the Australian megafires of 2019/20 resulted in the incineration of around 40 percent of the entire range of the Superb Lyrebird.

The scale of these fires was so great that the lyrebird 's survival status has been called into doubt. It is highly worrying that the conservation status has plummeted from "common" to potentially "threatened" from a single occurrence.

Losses on this scale of lyrebird populations would theoretically have far-reaching effects on forest ecology.

Understanding the role that species such as the Superb Lyrebird play in ecosystems is more important than ever in the face of climate change and an increased risk of extreme wildfires.

The forests of eastern Australia will be vastly different places without lyrebirds, with consequences reaching well beyond the loss of their glorious song to other species that rely on these "ecosystem engineers."

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