Turns out, it's not just humans (and some animals) that know nature is a medicine cabinet. New research has revealed how some clever birds are using preventative medicine to keep their nests safe. The med-savvy birds in question are russet sparrows (Passer cinnamomeus) in China that have been reported using wormwood (Artemisia verlotorum) leaves to keep parasites at bay and protect their young in a paper published in the journal Current Biology.
Researchers on the paper set up 48 nest boxes to study the behavior, and laced half of those with 5 grams of wormwood while the rest were bulked up with 5 grams of bamboo. Each day, they returned to the nests to either add nothing, more wormwood, or more bamboo to measure if and how much wormwood was being brought to the nests by the sparrows themselves.
Their results showed that the sparrows favored nests with more available wormwood and would bulk up on wormwood leaves over other available materials such as bamboo. The researchers believe that they are able to single out these leaves due to their odor, which is said to be rich and aromatic. Furthermore, those nests loaded up with the odorous leaves were found to have a lower instance of parasites, without which the sparrows’ offspring were able to grow plumper and heavier compared to parasitized nests. This confers a benefit for the birds though it’s not clear if they gather the leaves with the intent of protecting their young or whether it’s simply a behavior they have learned or inherited.
"Here we show that sparrows choose nest location and resupply established nests with fresh wormwood leaves using olfactory cues, that nests containing wormwood leaves have lower ectoparasite loads, and that nests with more wormwood leaves produce heavier chicks," wrote the researchers in their paper. "Our results indicate that sparrows use wormwood as a preventative medicine to control ectoparasites and improve the body mass of their offspring."
It's worth noting this is not conclusive. It could be that the birds like the smell, use it more often, and either passed on the genes that favor the wormwood smell, or it's a learned behavior.
However, the research adds to the evidence that it’s not just humans who benefit from medicinal substances in nature as these sparrows have shown they forage for materials that keep them healthy rather than keeping them fed or sheltered. Such behavior isn’t unheard of outside of Homo sapiens and the practice even has its own name: zoopharmacognosy. There are many creatures that use drugs in the wild including elephants, which eat Boraginaceae to induce labor.