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Russet sparrows use wormwood leaves to fight mites

Image: Wikimedia commons/Alpsdake CC-BY-SA 4.0

Does your family use chemicals – like bug spray – to keep insects and other creepy crawlies out of your house? An international team of scientists just found that some sparrows do too!

In China, russet sparrows use wormwood leaves in their nests. This herb is known to keep away parasites that could harm baby sparrows (chicks). But there were still questions to be answered. Do the sparrows put the wormwood there on purpose? And do the leaves actually protect chicks?

The team ran a series of tests to find out what was going on. First, they found that sparrows preferred to nest in boxes that smelled of wormwood. Next, when they took wormwood out of nests, the sparrows would go and get more. When scientists added extra, the sparrows collected less wormwood as a response. It was clear that the sparrows wanted wormwood in their nests.

Wormwood leaves contain a chemical that’s effective against mites. And the scientists saw that wormwood does its job in nests! Nests with more wormwood had fewer mites. And when the scientists weighed the young sparrows, they found heavier and healthier chicks in the nests with lots of wormwood.

As it turns out, sparrows aren’t alone in their use of wormwood. During the Dragonboat Festival in China, people hang branches of wormwood on their doors to protect against ill health, and bathe children in wormwood-infused water. Which raises an interesting question – who did it first?

Did you know?

Mites aren’t insects. Adult mites have eight legs! They’re arachnids, like their spider, scorpion and tick relatives.

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