Australia’s forest birds include colorful parrots, fluttering honeyeaters, bright blue fairy wrens and the humble ‘little brown birds’. Some, such as willie wagtails, laughing kookaburras, and rosellas, can be found in urban gardens. Others, such as swift parrots and regent honeyeaters, are exceptional rarities that bird watchers search for for days or weeks.
There are other woodland birds you may not have noticed, such as pardalotes, thornbirds, treecreepers, gerygones, and nightjars. There are forty forest bird species listed as endangered and several others descend.
And just this month there were another six forest birds added to the national endangered species list.
Efforts to help these species recover to be made. Common actions include replanting trees and placing nest boxes. But it’s important that we know which efforts make the biggest difference. We can then ensure that we do enough to restore these birds and focus resources on actions that work best.
Us systematic review collected all the published research we could find that tested the effectiveness of 26 conservation actions for forest bird communities. And yet we found little evidence on how effective most of these actions are.
Read more: We rely on expert forecasts to guide conservation. But even experts have biases and blind spots
Why don’t we know more about what works?
Australian forest birds are a well-studied group of species. However, research on the effectiveness of management for this ecological community is sparse. This limits our ability to develop general, evidence-based recommendations.
Some actions are definitely helpful. For example, we know that replanting trees and shrubs helps forest birds recover. It also helps to leave large pieces of dead wood on the ground – birds such as robins and treecreepers appreciate that.
However, many of the studies we reviewed did not compare sites where conservation action had taken place with ‘control’ sites – otherwise comparable areas where that action had not taken place. This made it difficult to compare the effectiveness of different actions. Because of this, we simply cannot know for sure which actions work best in different contexts and how big their effect is.
Read more: New research shows planting trees and shrubs brings forest birds back to farms, from beautiful fairy wrens to spotted pardalotes
We found surprisingly few actions that had been the subject of studies using control sites, where birds were studied at similar sites where no action had been taken. This even applied to common actions, such as the control of weeds, wild herbivores (goats, pigs, deer) and predators (cats and foxes), or the installation of nest boxes.
All of these actions probably have at least some benefits. However, without more studies and appropriate controls, we can’t say how big the benefits are, or which action makes the biggest difference.
Where the evidence exists, the results are mixed
Interestingly, four actions for which we were able to collect some clear evidence had mixed results. These actions were grazing management, prescribed burning, noisy miner control, and habitat protection. The evidence shows that their effects on birds depend on location and management context.
Read more: Should we cull noisy miners? After decades of research, these aggressive honeyeaters are still outsmarting us
Reducing livestock grazing had mixed results for forest birds. Sometimes the effects were positive, sometimes negative and sometimes it had no effect.
Prescribed burning was unlikely to increase forest bird numbers, with some studies showing no effect and others showing negative effects.
These conflicting results may be due to differences in bird communities, severity of threats, or differences in site habitat or climatic conditions, as well as in the landscapes surrounding the study sites.
They can also be explained by differences in how the management actions were performed (e.g. intensity, frequency, method) and monitored (e.g. time since the action took place). But because there were only a handful of studies, we couldn’t pick these reasons apart.
Despite the decline of Australian forest birds and continued investment in their conservation, we were unable to draw general conclusions about the overall effectiveness of 26 conservation measures for these species. We still don’t know which management actions are most effective for this beloved avian community. This knowledge gap is likely to be greater for less studied taxonomic groups.
So what can we do to fill in the gaps?
To give us concrete answers, there are two key messages for conservationists and researchers.
First, we need to do more research to test the effectiveness of managerial actions and understand the context in which different outcomes occur. These studies need rigorous study designs, appropriate controls, and careful statistical reporting.
Second, we encourage practitioners to take advantage of the online database of existing studies that we have collected and the corresponding ones annotated bibliography. These provide a wealth of detailed practical information about each management action. These resources are a comprehensive collection of the best available evidence to support forest bird management decisions.
We also encourage collaborations between practitioners and researchers to build the evidence base by evaluating management actions that are being implemented or soon to be trialled.
Unfortunately, these conclusions of “we need more research” and “it depends on the context” are not new. However, we now have a clear picture of the knowledge gaps.
In the meantime, preventing damage and habitat loss is the most important thing we can do in the first place.