Natures wonders: injured plants invite birds for protection (Introduction)

by David Turell , Tuesday, August 14, 2018, 20:03 (2291 days ago) @ David Turell

The injury draws insects, which attack the plants. The plants emit volatile attractants to birds which can to come and eat the insects:

https://phys.org/news/2018-08-scientists-emitting-scent-cues-birds.html

"When plants are in distress or being fed on by insects, they have been known to send out sensory volatile cues that alert organisms in the area—such as birds—that they are in need of help. While research has shown that this occurs in ecosystems such as forests, until now, this phenomenon has never been demonstrated in an agricultural setting.

"Researchers at the University of Delaware have recently found that agricultural plants also send out these signals when under duress from insects, opening new potential avenues for growers to defend their crops while at the same time providing a much-needed food source for birds.

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"Using a field plot of maize on UD's Newark farm, the researchers attached dispensers using a synthetic odor blend that replicated the volatiles—odor cues given off by plants to indicate they are being attacked such as the smell of freshly cut grass—attached to corn stalks. They also used dispensers using only an organic solvent as a control measure.

"The Play-Doh larvae with orange head pins were then distributed on plants around the volatile dispensers and the organic solvent dispensers with the researchers measuring the bird attacks or pecks on the larvae.

"They found that the imitation larvae located closer to the volatile dispensers had significantly more attacks than those located closer to the organic solvent dispensers.

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"Hiltpold said the results support growing evidence that foraging birds exploit volatile cues and a more accurate understanding of their behavior will be critical when implementing pest management programs benefiting from ecological services provided by insectivorous birds.

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"It is a cry for help," said Hiltpold. "The plant is damaged, the plant emits something that recruits help and we're all thinking it's help from other insects but it seems that birds are also using that as a cue to locate a plant or a group of plants. Then what we think is that they use their visual equity to locate the larvae when they're in the vicinity of the plant emitting the volatiles."

"Hiltpold said that their research in the field confirmed this, as they had one larvae located on a volatile dispenser on a plant, and then four larvae distributed on all the plants around the plant with the dispenser.

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"When they compared the number of pecks to the larvae on the plant with the dispenser to the number of pecks on the larvae on plants around the dispenser, there was no significant difference.

"This means that the bird is coming, smelling the volatiles and when it gets to the vicinity of the plant that is damaged, then it visually searches for the insect," said Hiltpold.

"It is also interesting because birds have long been believed to not be able to smell, but this research indicates that they are smelling the volatiles and then coming in closer to visual locate their prey.

"'Whether or not birds can smell is a big question because they apparently lack some anatomical things to smell the way other vertebrates are smelling," Hiltpold said. "Yet, they seem to have the capability of sensing volatiles but we don't exactly know how they do it yet.'"

Comment: How did the plants learn what would attract birds? Not by chance.