Seeds from aquatic plants have been known to successfully germinate even after passing through the digestive tract of a bird – this is one method by which plants can spread from one body of water to another.
Sometimes, though, seeds don’t make the full, daunting journey through a bird’s bowls.
“Regurgitation, or vomiting, is a common behavior in the daily life of many bird species,” write the authors of a paper recently published in the journal Aquatic Botany. If a plant seed is thrown up before passing all the way through a bird’s body, thereby “circumvent[ing] many of the damaging digestive processes,” so much the better for the seed.
The scientists, interested in whether or not the seeds of aquatic plants might spread via bird vomit, fed ducks seeds collected from 10 species of wetland plants. The ducks regurgitated seeds in about half of the 64 feeding trials the researchers conducted, seemingly in response to one of two conditions: overfeeding, or eating large, indigestible seeds.
If the birds ate a lot of food in a short time (as they sometimes do in the wild, when they happen upon an abundant food source), they threw up some of the seeds they had recently eaten, regardless of seed size, within three hours of eating. Large (more than 10 millimeters, or a little bit less than half an inch), tough seeds were sometimes regurgitated early on in response to overeating, but also between 11 and 24 hours post feeding, apparently after the seeds were rejected from the birds’ gizzards due to their size.
“As regurgitation in birds requires a suffocate movement which is impossible during flight,” the scientists note, “regurgitation most likely occurs after landing in wetland habitat,” meaning that bird vomit may be an important way for aquatic plants to spread.
Seeds from the aquatic plant Iris pseudacorus were among the largest seeds fed to ducks (and later regurgitated by them) during feeding trials.
(Original image by Paul van de Velde via Flickr/Creative Commons license)