On a postcard-perfect May day in the hills of West Brookfield, Roz Renfrew is listening for the sounds of-- R2D2? It's not a droid she's looking for, but a bird called the bobolink that sings a call that she says sounds like it's right out of the Star Wars movies.
"They're just fun. They're fun to watch," she said.
But when walking through the fields near her house, she says these days she's seeing fewer birds and more of something else.
"We're seeing more and more invasives showing up in these fields," Renfrew said.
A problem Renfrew says she sees growing statewide.
"I started hand-pulling them," she said. "But I couldn't keep up with them."
These plants aren't just annoying for landowners; experts say they're bad for Vermont's birds.
"The invasive plants are a growing threat that we don't know a lot about yet, but it looks a bit ominous for them," Renfrew said.
If there's someone that knows about birds in the state, it's Roz Renfrew. She wrote the book on them-- literally. It's only been in the last few years, she says, researchers have started to study the problems with birds and invasive species. In particular, experts are discovering that two really common plants in the state are doing damage. One is honeysuckle.
"It comes from Europe and Asia, but you can tell the invasive, non-native by cutting the stem. And if the stem is hollow or brown, that's the one from away," said Rose Paul of the Nature Conservancy.
The other is buckthorn.
Both are invaders taking over the state slowly but steadily.
"Both of these species are expanding across Vermont," Paul said.
Invasives expert Rose Paul says they hurt the birds in multiple ways.
"These things like honeysuckle and buckthorn are really manipulating the birds," she said.
Paul says the buckthorn lures birds in with bright berries that seem appealing, but then don't provide the nutrition they need to make their migrations.
"If we were about to run a marathon, and we ate a big bag of potato chips, that wouldn't work so well for us. It's the same with the birds, they're about to head out on a long journey and they're filling up on junk food," Paul said.
And the results are starting to be noticed.
"People have documented that songbirds will get really weak when they fill up on buckthorn then take off on a migration flight. They become very weak, it's very bad for the birds," Paul said.
And as honeysuckle sucks up space in forests, birds are building their nests in it to a devastating effect.
"Scientists have shown there's more predation of the nests, that carnivores come in and eat more of the nestlings and the eggs," Paul said.
And wildlife experts fear as these invasive populations increase, some bird populations will decline.
"You might see more of the birds that are already common and fewer of the birds that we're concerned about-- that are the less common birds-- becoming even less common," Renfrew said.
Wildlife experts say the best way people can help with invasive species like this one, is to actually do a simple weekend do-it-yourself project where you get the invasive species off your land and replace it with a native one. One suggested alternative-- the Juneberry.
"That has beautiful white flowers this time of year. And then in June it has berries that taste a lot like blueberries. We like to eat them and so do the birds," Paul said.
Experts say the key is trying to keep the local trees and plants thriving, which in turn will help birds like the bobolink.
"Probably my favorite bird period," Renfrew said.
Back in the fields, Renfrew hears what's she's looking for-- the bird version of a famous droid. A bobolink recently returned to the Green Mountains for the summer.
After a while, the bird flies away. The fear is if these invaders continue their takeover, one day it may not fly back.