Forgetting Abundance

Many Australians are noticing it, even if they haven’t quite put their finger on it.

There seem to be fewer birds around - especially smaller ones. The dawn chorus is quieter. Windscreens collect fewer insects than they once did. Fairy-wrens and flycatchers seem less common. You might assume this is simply nostalgia. But unfortunately, the science increasingly suggests otherwise.

A new Canadian study published in the Proceedings of the National Academy of Sciences just found that flying insect populations at a long-term monitoring site declined by more than 60 per cent since the 1970s. And the consequences are now showing up in birds. Tree Swallows, which feed almost exclusively on flying insects, are becoming smaller, producing fewer young and struggling to maintain their populations. The decline in insects is thus now flowing directly through the food web.

The findings come as little surprise to ecologists. Insects are the foundation of many terrestrial ecosystems. They pollinate plants, recycle nutrients and provide food for countless birds, reptiles, mammals and amphibians. When insect populations crash, the effects ripple through entire ecosystems. And while the study was conducted in Canada, there’s every reason to believe similar processes are occurring in Australia.

Australian researchers have already documented widespread declines in woodland birds across south-eastern Australia and identified insect decline as a contributing factor. Many of our most familiar birds depend heavily on insects, particularly during breeding season when chicks require protein-rich food. When insects become less abundant, birds raise fewer young and populations decline.

Climate change is making the problem worse. Many insects emerge according to temperature and seasonal conditions. Birds, meanwhile, time their breeding according to day length, rainfall and other environmental cues. As climate change alters seasonal patterns, these relationships become disconnected. The peak abundance of insects may no longer coincide with the period when hungry nestlings most need food. The Canadian study found evidence that this mismatch has been increasing for decades.

Australia is already seeing climate impacts on birds. Researchers have documented changes in bird size, breeding behaviour and survival associated with rising temperatures and shifting weather patterns. Recent research on Canberra’s superb fairy-wrens found climate change was driving cumulative impacts on survival and reproduction, with implications not only for fairy-wrens but for insect-eating birds more broadly.

This matters because birds are more than just beautiful. Birds control insects, disperse seeds, pollinate plants and act as indicators of ecosystem health. When bird populations decline, they’re often telling us something important about the environment around us.

The Australian Government’s own State of the Environment reporting - heavily vetted to downplay environmental impacts - paints a worrying picture. Many bird populations are declining, and threatened bird abundance has fallen dramatically over recent decades. Almost one in six Australian bird species is now threatened with extinction.

Yet there is another danger that receives far less attention. Scientists call it “shifting baseline syndrome”. The idea is simple. Each generation accepts the environment they grow up with as normal. If bird populations fall by half over several decades, older people notice the change because they remember what came before. Younger people don’t. Their baseline is already lower. Over time, society loses its memory of abundance. And it gets worse with each generation.

A child growing up today may never know what Australian landscapes are supposed to sound like - when bird populations were larger and insect life more abundant. A generation from now, even further declines will become accepted as normal. Scientists increasingly recognise shifting baseline syndrome as one of the major psychological barriers to biodiversity conservation because people struggle to protect what they never knew existed.

This is perhaps the most insidious aspect of biodiversity loss. Species disappear gradually. Ecosystems become quieter. The losses occur slowly enough that many people barely notice them. There’s no single catastrophe. No dramatic moment. Just a steady erosion of life that becomes normalised with each passing decade.

This latest study from Canada is therefore about much more than one bird species on the other side of the world from Australia. It’s a warning. A warning that insect declines matter. A warning that climate change and biodiversity loss are deeply interconnected. A warning that protecting habitat alone may not be enough if climate disruption continues to accelerate. And a warning that if we’re not paying attention, we risk accepting ecological impoverishment as the new normal.

Birds have always been among the most visible and beloved parts of the natural world. Their songs accompany our mornings. Their migrations mark the seasons. Their presence connects us to Country and to place. If they’re telling us something, we should listen.

I took this photo of a Splendid fairy wren back in 2015.