Want to make cacophonous miners less tyrannical? Think twice before filling your garden with nectar-rich flowers

Boisterous miners are convoluted creatures. These native Australian honeyeaters live in gigantic cooperative groups, using alarm calls to target specific predatorsand sometimes help raise other miners’ children. But they are probably best known for their aggressive and coordinated attacks on other birds – a behavior known as “mobbing.”

We conducted a study investigating some of the possible factors influencing mobbing. We were interested in whether access to human food left on plates in cafeterias or a high supply of nectar from planted gardens might give urban miners extra energy and time to mob other species more often. We also investigated whether miners were more aggressive towards some species than others.

Our testpublished in the magazine Emu – Australian Ornithologyfound that it wasn’t the cafeterias with access to sugary foods that led to more aggression in miners. In fact, gardens were the place where we recorded the most aggressive behavior.

Understanding the phenomenon of mobbing is crucial because this type of behaviour can displace other birds and reduce species diversity. Smaller birds with a similar diet to which cacophonous miners are particularly vulnerable.

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Read more: Should we cull cacophonous miners? After decades of research, these aggressive honeyeaters are still outsmarting us

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What did we do?

The preferred habitat of the cacophonous miner is the edges of open eucalyptus forests, including cleared areas and the outskirts of towns. Their numbers adult in recent decades, presenting a significant protection problem.

We know from previous studies that cacophonous miners in cities are usually more aggressive than miners in the countryside.

However, to take a closer look at bullying behaviour, we placed museum stuffed animals of different bird species in three different habitat types around Canberra:

• city ​​cafes with lots of leftover food

• city ​​gardens where there was more nectar than usual

• areas of scrub more typical of the “natural” habitat of the mineworm.

Then, in each habitat, we presented the cacophonous miners with three different types of museum-quality stuffed bird models:

• nutritional competitors with a diet similar to the miners, both the same size (musk deer) and a much smaller species (spotted pardalote)

• potential predators, including a perilous species that preys on miners (the red-tailed hawk) and a species that robs nests but poses less of a threat to adult miners (the pied currawong)

• a neutral species, i.e. a bird that does not hunt mining insects and does not compete with them for food (in our research we used the eastern rosella model).

We wanted to see how miners would react to these “intruders” in different situations. We also set up a loudspeaker nearby to broadcast alarm signals to see how miners would react.

What we found

We found fascinating differences in the way miners responded to our taxidermy models and the alarm signals we broadcast.

Boisterous miners showed aggressive behaviour for significantly longer periods in gardens and cafes compared to natural wooded areas.

Surprisingly, however, access to sugary cafeteria food did not result in the most aggressive behavior. Instead, we found the highest levels of aggressive behavior near the gardens.

Nectar-rich plants (such as grevilleas and bottlebrushes) are attractive to birds with a sweet tooth, and miners are no exception. Newer varieties flower for longer, meaning that miners living in our gardens can have access to an almost year-round food source.

Straightforward access to these flowering shrubs may influence aggression, providing more time, energy, or reward to cacophonous miners defending these incredibly affluent resources.

The type of model presented also influenced the miners’ reaction.

More miners were attracted to an area and stayed near the object longer when the model was a predator.

However, miners showed even greater aggression toward food competitor models. They were more likely to physically hit food competitor models by pecking or diving compared to predator models.

What can gardeners do with these discoveries?

Our research shows how crucial it is to consider how gardens – whether in backyards, parks or fresh housing estates – can impact local ecosystems, including bird behaviour. Previous studies discovered a link between the plant species people choose to plant and the local diversity of bird species.

To reduce the risk of your garden becoming the perfect habitat for despotic miners, you should:

• Plant different levels of plants in your garden – this means adding ground cover, tiny shrubs, medium shrubs and trees to provide shelter at different heights for different birds and animals

• consider planting lots of dense shrubs with tiny flowers that will attract insects and provide shelter for tiny birds

• employ a mix of nectar-rich and non-flowering shrubs and grasses (instead of focusing too much on flowering plants)

• try to avoid planting too many exotic species; choose native plants instead local to your area and adapted to the climatebecause they benefit native plants and animals while minimizing benefits to aggressive and cacophonous miners.

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Read more: Why we “hate” some birds and why their behavior may be our fault

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