bustard heaviest living bird that can fly. Despite a wingspan reaching around 2.6 meters, its weight near 16 kilograms sits at the upper limit for flight. It is the largest bird native to the Iberian Peninsula. Yet a standout trait of these birds is their tendency to seek out two plants that harbor compounds capable of killing pathogens, a practice observed in traditional medicine.
In this sense, bustards may provide a rare example of avian self-medication. A recent study published in Boundaries in Ecology and Evolution highlights this possibility.
“We are observing a pattern where bustards prefer plants containing compounds with antiparasitic effects in vitro,” explains Luis M. Bautista-Sopelana, a scientist at the National Museum of Natural Sciences in Madrid and the first author of the study.
Co-author Azucena González-Coloma, a researcher at the Institute of Agricultural Sciences in Madrid, adds that the team examined two weeds also used in human traditional medicine. The research shows that both plants possess antiprotozoal and nematicidal properties, while one of them also contains antifungal agents.
Animal self-medication is suspected across a broad range of species, including primates, bears, deer, macaws, bees, and fruit flies. However, Bautista-Sopelana cautions that proving this in wild animals is challenging. Direct experimental control comparisons and double-blind trials are not feasible in field studies, making definitive conclusions difficult.
Bustards are classified as Vulnerable on the IUCN Red List. They breed in grasslands spanning Western Europe and Northwest Africa to Central and East Asia, with about 70 percent of the world’s population residing in the Iberian Peninsula. Males can reach weights of up to 16 kilograms.
Females typically stay within their spawning range for life, a period of about 10 to 15 years, while males return to the same general area each year after dispersal. Prolonged residence in the same area increases the risk of re-infection and elevates the chance of reintroducing parasites through fecal matter. Males also require exceptional stamina during the mating season when immune defenses are expected to dip.
Plants with active compounds against diseases
Researchers note that both sexes of bustards may benefit from gathering herbs during the mating season when disease pressures rise. Birds that consume plants with disease-active compounds might appear healthier, stronger, and more attractive to potential mates, according to González-Coloma.
Teams studying bustards have tracked the birds since the early 1980s, focusing on Madrid and Castilla y León. A total of 623 sightings were recorded for both female and male birds, including 178 observations during April, the peak of the mating season. Using microscopic analysis, researchers counted the abundance of identifiable plant remains such as stems, leaves, and flowers from roughly 90 plant species known to be on the bustard menu.
The findings showed that two plant species were consumed more frequently than expected given their availability: corn poppy, also known as Papaver rhoeas, and purple viper’s bugloss, Echium plantagineum. These species are known to harbor bioactive compounds relevant to plant and animal health.
During April, the peak energy expenditure of the mating season, reptiles also show a preference for these plants, with males displaying a higher reliance on them than females. The researchers note that the shift aligns with periods when both energy demands and disease exposure are greatest.
Laboratory analyses indicate that extracts from both plants strongly inhibit or kill protozoa and nematodes in vitro, with purple viper’s bugloss also showing moderate antifungal activity. The study concludes that bustards are prime candidates for self-medication through specific plant choices, though it also emphasizes the need for more research to confirm these effects in the wild.
Conclusive proof of self-medication requires experimental protocols aligned with biomedical, veterinary, and pharmacological standards. This work provides a compelling foundation for understanding how wild birds may manage disease risk through plant selection. [Citation: Frontiers in Ecology and Evolution, 2022]
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Note: The environment department’s contact details are not included in this article. The information herein is based on peer-reviewed research and field observations documented in the cited study.