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Nanaimo researcher studying bushtit sex identification

VIU student Chelsey Watts doing field work and genetic testing to learn more about bird species

Identification of whether a bushtit is male or female has historically relied on the bird's eye colour, a less-than-ideal method considering the eye colour is also believed to change with age. 

Chelsey Watts, a student researcher at Vancouver Island University, is using a mixture of field work and modern genetics to try to either confirm or deny the accuracy of these methods.

"There is no actual research that shows that's correct," Watts said. "So the point of my research is I'm going to collect some DNA samples from them and then confirm using DNA and match it with photos of their eyes to confirm that, 'Yes, the light yellow eyes are females and the dark eyes are males.'"

Just slightly larger than an adult hummingbird, bushtits are grey-coloured non-migratory songbirds that live in dense brush throughout western North America. Relatively little research exists on the species.

"As field biologists out in the field, when we're doing population studies on animals, one of the key factors we need to know is the number of males and females in the population," Watts said. "That allows us to predict the effective breeding size, which predicts the number of young individuals that will be born into the population each year. By monitoring this we can tell if populations are growing, if they're declining or if they're staying the same." 

The bird's main diet is insects and seeds. Watts said the species exhibits helping behaviour, something rare in birds, where those without young may assist those with young in feeding and sitting on eggs.

"Bushtits are quite communal for birds so you'll often see them in large groups or flocks. So when we catch them we usually catch four or five at least, and there'll probably be more in the trees around them."

To collect samples, Watts uses the Buttertubs Marsh bird-banding station operated by VIU professor Eric Demers. 

Founded in 2013, the site is open once a week, allowing the trained volunteer researchers to open polyester mist nets, scattered around a central station. The birds are unable to see the narrow threads and fly into it, becoming harmlessly tangled. Removing them is a methodical process of holding the bird while untangling the threads, requiring specific training by Demers. If done incorrectly, it could very easily harm the animal. 

"This is the riskiest part of everything we do, it's getting them out safely," Demers told the News Bulletin. "That's why it's important to train everybody the same way and making sure it's consistent." 

Once removed, researchers move the bird using a "bander's grip" into a cloth bag for transport back to the nearby station. 

At the station, the bag is weighed before the bird is banded with a small metal tag on its leg using specialty pliers. All banding sites use the same tagging system, resulting in long numbers that are unique to that specific bird.

After measurements are taken, including its height, approximate age, wing length and body fat, the bird is released.

"There's a lot more research on birds being done in eastern North America…" Demers said. "Often on the West Coast there's not as much research done because there just isn't as many universities [or] researchers out here so [the bushtits] are a bit of an understudied species."

For Watts's particular research, in addition to recording eye colour, she typically takes a sample of two tail feathers. In the case of younger bushtits, body feathers may need to be taken due to the tail being in the early stages of growth.

"In the lab I will have to do DNA extraction," Watts said, "which usually involves using a digestive enzyme that basically breaks open the cells so the DNA can get out into solution, then I will … amplify the specific gene I'm looking for which will be on the sex chromosome of the bird."

DNA extraction is planned to take place in September, with a final report anticipated next spring.

Watts said conserving bird species is an important cause to her.

"One of my favourite things about walking outside in nature is hearing the birds sing and I don't want to live in a world where that doesn't exist," she said. "So I hope everybody can try their best in any way they can to help conserve the habitats that are important for birds to thrive."

Jessica Durling

About the Author: Jessica Durling

Nanaimo News Bulletin journalist covering health, wildlife and Lantzville council.
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