Bird communities in a land of droughts and flooding rains: riparian tree cover as climate refugia

This post, co-authored with Angie Haslem and Andrew Bennett, originally appeared on The Applied Ecologist’s blog

Something alarming happened in the woodlands of southern Australia last decade. The birds stopped calling. Well, not entirely, but substantially. The chorus of kookaburras, honeyeaters and babblers that usually make the woodland air burst with song was reduced to a whisper.

And we think we know why. The region was gripped by a record-breaking drought, known now as the ‘Millennium Drought’, which spanned nearly a decade from 2001–2009. The drought crippled the region’s biodiversity: frog populations crashed, and over half of terrestrial bird species declined.

Kookaburra (left) and grey crowned babbler (right). Photos courtesy of Rohan Clarke (
Kookaburra (left) and grey crowned babbler (right). Photos courtesy of Rohan Clarke (

When the drought broke spectacularly in 2010 with flooding rains, there was a sense of cautious optimism that the region’s biodiversity might have been offered a reprieve. However, two years after the drought had broken, that optimism turned again to alarm. Monitoring data revealed that although around one quarter of bird species increased following the floods, most species had not recovered. Further still, 14–29% of species (depending on the dataset) continued to decline, despite the drought ending. Promisingly, in our recent paper in Journal of Applied Ecology, we think we have found a hint of a silver lining.

If you read the climate change literature, you may be familiar with the idea of ‘climate refugia’. This concept suggests that some areas are buffered from the impacts of climate change or climatic extremes such as drought. For instance, areas that have relatively high moisture or stable microclimates may offer refuge for species during drought. It follows that these areas should be targeted for protection for conservation, to enhance the capacity of biodiversity to persist during climate change.

The concept provides a sense of agency among conservationists in the face of a looming global disturbance over which we have little control. However, although there is evidence of refugia operating over evolutionary time scales and at continental spatial scales, the evidence that we can create refugia at the scale of conservation management is much scarcer.

Our paper provides that evidence. We found that landscapes with more tree cover on productive soils – such as on riverbanks, stream sides, drainage lines and floodplains, collectively termed ‘riparian vegetation’ – retained a higher proportion of their bird species during the drought.

A typical riparian strip in the study region.
A typical riparian strip in the study region.

This means that past land clearing, for agriculture and other human land uses, is likely to have diminished the capacity of bird communities to resist the impacts of drought. This might explain why the drought had such huge effects on the region’s bird fauna. On the other hand, by protecting riparian vegetation, and by revegetating cleared riversides, floodplains and drainage lines, we could enhance the capacity of bird communities to persist during the next big drought. That is, we could build climate refuges.

Although this sounds promising, our results come with an important caveat. When the drought broke, landscapes with less riparian tree cover tended to ‘bounce back’ to a greater extent. That is they were more ‘resilient’. This is largely because these same landscapes had a greater need for recovery, having lost a greater proportion of their species pool during the drought. By contrast, landscapes with more riparian tree cover lost fewer species and so had less of a need for recovery post-drought. Over the duration of the entire drought–flood cycle, these two opposing trends cancelled each other out such that two years after the drought, a similar fraction of the bird community was lost across all landscapes.

What does this mean? In simple terms, riparian vegetation enhances the ability of landscapes to retain bird species during the drought, but does not arrest longer-term declines that may cause ongoing species loss over successive drought events.

This does not diminish the important role of riparian vegetation for bird conservation during drought. Retaining a larger portion of the species pool throughout the landscape means that ecological functions continue, functions critical to ecological and economic systems, such as pollination and insect control.

Cleared (left) and vegetated (right) riparian strips in the study region.
Cleared (left) and vegetated (right) riparian strips in the study region.

We also know from previous work in these same landscapes that increasing tree cover of any kind increases the richness of woodland birds. Indeed, the total amount of tree cover in the landscape is the most important influence on the number of woodland bird species that can occur. Adding riparian tree cover to heavily modified landscapes gives huge ‘bang for your buck’ in terms of bird conservation, as productive areas support more species and provide specialised habitat for species that favour riparian vegetation. Finally, other work has revealed that landscapes with more tree cover had more stable bird communities, measured in terms of species turnover, over the duration of the drought.

Combined, these results suggest that maintaining and revegetating riparian areas will provide many benefits to bird conservation. It also has many other benefits, including protecting water quality, enhancing aquatic environments, and creating a visually attractive environment. It’s a ‘win-win’ for sustainable land management and nature conservation.

It’s bush poetry time!

Last year at the Ecological Society for Australia’s annual conference I presented some research as a bush poem (you may recall Corey Bradshaw posted the poem on his site). I’ve had a few request for the poem since then, so I finally got around to recording it. It just happens that the research mentioned in the latter part of the poem is now online in the Journal of Applied Ecology

Andrew 'the aristocrat' Bennett and Ralph 'the drover' Mac Nally
Andrew ‘the aristocrat’ Bennett and Ralph ‘the drover’ Mac Nally star in ‘The Old Grey Box of Heathcote Town’

With lead roles by famous ecologists Andrew Bennett, Jim Radford and Ralph Mac Nally, without further ado, The Old Grey Box of Heathcote Town

Why did the male plover turn into a night owl?

Nature is full of trade-offs. To excel at one thing, often means you’ll end up sucking at another. Sad but true.

Take ornamentation for example. Flashy, decorative adornments that species parade to lure in a member of the opposite sex work well when finding a mate, but they also have their drawbacks. In a world full of predators searching for their next meal, being adorned like lady gaga might just make you stand out a wee bit.

Lady gaga's outfits look outstanding, but you wouldn't want to look like that when surrounded by lions and tigers and bears (oh my).
Lady gaga’s outfits look outstanding, but you wouldn’t want to look like that when surrounded by lions and tigers and bears (……….oh my).

In our recent paper  in Proceedings of the Royal Society of London B, we found that’s the case for the adorable red-capped plover. This species displays sexual dichromatism. That is, one sex displays ornamentation and the other does not. As is often the case in birds, the sex that has the showy plumage is the male. These guys have a bright red head, and the females love it.

A male (right) and a female (left) red capped plover.
A male (right) and a female (left) red capped plover. Photo from

Sadly, this red head acts like a beacon for visual predators, threatening not only the male plover, but also exposing their precious eggs to an enhanced risk of predation. You see, male plovers are pretty good dads. They do their fair share in terms of helping around the nest. They incubate their eggs around half of the time, with the other half being tended to by the female.

But their caring nature is undermined by their showiness. Using models of red capped plovers, we found that when males attended the nest during the day, there was a huge increase in the probability that eggs within that nest would be preyed upon by diurnal visual predators (largely ravens).


But nature has a way of findings solutions too. Red capped plover’s love their red heads, and they weren’t going to give them up without a fight. If diurnal predators were the issue, then there’s only one option: night shift. We found that male and female plovers had a strict schedule for when they would attend the nest, with males attending the nest mostly at night when those diurnal, visual predators were asleep, whereas the less conspicuous females attended the nest during the day.


And so, with a little bit of flexibility, the red capped plover shows it is possible to look good and be a caring, sharing dad.

New paper: Incorporating anthropogenic effects into trophic ecology

Last year I spent six weeks with Joern Fischer and his posse (yep, he has a posse) bird watching, playing carom, and generally Germany-ing it up.

Carom is a game played all over the world, but mainly at Dave Abson's place in Lüneburg, Germany.
Carom is a game played all over the world, but mainly at Jan Hanspach’s place in Lüneburg, Germany.

Although the beer was alarmingly cheap, I did manage to use some of my time in a productive manner. This week, the fruits of that productivity have ripened, and are now ready to be plucked from the tree, diced finely, and added to a glass of gin and soda water.

In case you need me to spell it out for you, we’ve published a paper.

What’s it about? I’m glad you asked.

Joern and his posse ran a big research project in a very cool part of the world: Transylvania, Romania. This region is undergoing a transition from traditional to more modern, industrialised farming practices and Joern and his team are trying to figure out what that means for the people and biodiversity that call the place home.

Transylvania has a very interesting set of large mammals, including carnivores such as bears, wolves and foxes, and herbivores such as red deer and roe deer. These species occur along with the people of Transylvania and their dogs that help look after livestock. The paper examined how these species co-exist, and what are the main drivers of their occurrence throughout the landscape.

We used camera traps to monitor these species and an important aspect of this work was that we treated humans like any other species: if we recorded them on a camera trap, we could calculate an index of local human activity, much like we often do with other species.

We then modelled the entire ‘ecosystem’, including humans, to show the relative effect of people on other species, compared to the effects of species on each other. We had some expected results, such as the suppressive effects of large carnivores on herbivores. However, these effects pale in comparison to the effects that humans have on species from all trophic levels. Our work highlights the need to think about people as part of the network of species within a region.

The paper is published in Proceedings of the Royal Society of London B.


New paper: Vive la resistance: reviving resistance for 21st Century conservation

Ask a person on the street ‘what does it mean to be resilient’? They might answer something to the effect of ‘the ability to bounce back following adversity’.

Ask a second year ecology student ‘what does it mean for an ecosystem to be resilient’. They might recall their first year lecture where they learned about resilience, the ability of an ecosystem to recover following disturbance. They will probably also mention the closely related concept of ‘resistance’, the ability to persist during the disturbance.

Now, ask an academic or postdoc in ecology ‘what does it mean for an ecosystem to be resilient’ and they will often look perplexed. That first year understanding, plain and simple, creeps into their might, along with the dictionary definition of the term. BUT, then a bunch of other terms…Panarchy? Hysteresis? Um, adaptive cycle…multiple stable states?

It was this reaction, by fellow academics, students and land managers, that led to my most recent paper: Vive la resistance: reviving resistance for 21st Century conservation, published online in Trends in Ecology and Evolution.

The message: let’s get back to basics. The textbook definitions, which we call the ‘resistance-resilience framework’, are actually pretty decent. It’s simple and intuitive.  It’s a conceptual model of course, and so it will not always be applicable or relevant. However, it has a bunch of neat attributes that other concepts of resilience lack.


So, long live resistance!

New article in The Conversation: Mourn our lost mammals, while helping the survivors battle back

Together with colleagues Euan Ritchie and Tom Newsome, I’ve published an article on The Conversation drawing attention to the radical changes in Australia’s mammal communities since European arrival, calling for more support for projects that seek to ‘rewild’ Australia by re-introducing native predators.

Gone from this earth: Four of the 30 Australian mammal species that have gone extinct since European settlement. The desert rat-kangaroo (top left), the eastern hare-wallaby (top right), the white-footed rabbit-rat (bottom left), and the pig-footed bandicoot (bottom right)
Gone from this earth: Four of the 30 Australian mammal species that have gone extinct since European settlement. The desert rat-kangaroo (top left), the eastern hare-wallaby (top right), the white-footed rabbit-rat (bottom left), and the pig-footed bandicoot (bottom right)