A bird in hand: How a Smithsonian zoologist spent the pandemic tracking nectar-stealing orioles | Smithsonian Voices

While most nectar-eating birds stick their head directly inside the flower, which coats their head in pollen, the orchard oriole sometimes pierces the base of the flower with its beak to drink the nectar without covering itself in pollen. . As a result, he gets the sweet reward without having to do the pollination work.
Gary Graves

Every day in the summer of 2020 and 2021, Smithsonian research zoologist Gary Graves stepped out into his garden in the Ozark Mountains to face a familiar crime scene: the vibrant orange blossoms of his trumpet vine littering the ground, the flowers full of holes and jagged. The author: a small herd of chestnut and yellow orchard oriole. It documented the extent of daily vandalism, as did forensic analysis.

When the COVID-19 pandemic hit in 2020, the Smithsonian National Museum of Natural History closed and few museum staff were allowed entry. At the time, Graves was in the middle of a project studying vulture microbiomes, but the pandemic put that project on hold. Unable to conduct his regular research at the museum, Graves traveled to his vacation home in the Ozarks to telecommute, about a thousand miles west of DC.

During the summer months, he noticed a persistent pattern of birds stealing nectar from the flowers in his garden. He quickly recognized this behavior as unusual and unstudied and decided that his next research project would be to characterize this behavior occurring in his own backyard.

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A curator and research zoologist in the museum’s bird division, Graves moved to his vacation home in the Ozarks during the pandemic. Here he came across a new research project in his own backyard.

Marc Robin

“The museum banned me from doing research trips and I couldn’t get permission to do field research, so I was stuck in my backyard,” Graves said. “But then I thought, ‘Here’s something I can do.'”

What makes nectar theft particularly unusual? After all, the sole purpose of nectar is to be consumed by animals. However, not all sips of nectar are created equal. Graves describes three different types of nectar consumption: legitimate pollination, nectar stealing, and nectar stealing.

The first follows the common story of pollination – an animal co-evolves with a flowering plant in a way that results in a mutually beneficial scenario. The animal, such as a bee or a hummingbird, pollinates the flower and receives nutritious nectar from the plant as a reward.

“And it’s a nice clean story,” Graves said. “But in every system there are always free riders and cheaters.”

These free-riders and cheaters are the nectar-stealers and thieves. Nectar thieves are those who take the nectar without pollinating the flower but otherwise cause no harm. The anatomy of flowers usually matches their co-evolved pollinator like a lock and key, helping pollinators live up to their namesake while enjoying their sweet nectar treat. Nectar thieves circumvent this pollination system, taking the reward without fulfilling their end of the bargain.

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The smallest North American oriole species, the orchard oriole divides its time between the eastern half of the United States, where they breed and lay their eggs in pouch-like nests, and Central America.

Dan Pancamo, Flickr

“So a nectar thief is like a shoplifter, but a nectar thief is someone who takes a hammer to a jewelry store.”

This ruinous behavior can eventually stop the reproductive potential of the plant. Thieves tear flowers entirely or provide an easy shortcut to the nectar reward, such as a borehole through flower petals, to deter legitimate pollinators from doing their job.

Since the plant cannot fight back, the only defense it has is to evolve in some way to minimize or circumvent the effects of the oriole’s nectar flight.

According to Graves, avian nectar theft is not as well known in North America as it is on other continents. Observations of the trumpet vine have interesting implications in the broader field of pollination biology. So Graves took the opportunity to document it himself during the lockdown.

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Due to its colorful flowers, the trumpet vine attracts both gardeners and a range of pollinators like ruby-throated hummingbirds. But the garish plant also attracts its fair share of sleazy thieves and nectar thieves.

Gary Graves

Every morning, Graves went out to assess the damage: how many flowers did these birds spoil? What method of destruction did they use? Have their methods changed? He wrote it all down on a spreadsheet and did it for over 40 days in 2020 and 2021. Now his article describing the chaos method appears in the journal Scientific reports.

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The consequences of a theft of nectar: ​​cut flower petals litter the garden of Graves.

Gary Graves

The main finding Graves described was that the orioles wreaked havoc on the plant’s reproduction while they were there. Birds bored holes and stole nectar from over 90% of the plant’s flowers, and the plant did not bear fruit until the orioles left the area on their fall migration. Extending the blooming season beyond the bird departure date may be the only way for this population of trumpet creepers to reproduce.

Findings aside, Graves believes the main take-home message from the paper is that the opportunity for scientific discovery is everywhere. You don’t have to travel great distances or have fancy equipment to make remarkable scientific discoveries – the next discovery might be hiding in plain sight in your backyard. But like all good detectives, scientists must have a curious eye.

Related stories:
How the pandemic has changed scientific exploration
Get to know the planet’s pollinators and other natural history programs in June
Meet one of the curators behind the Smithsonian’s 640,000 birds

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