Julia Plummer's favorite birdsong is a chorus of long-tailed ducks. “The first time I heard a raft of male long-tailed ducks all calling out together, I was like, Oh wow, I’ve never heard anything like this,” she says. “The sound is so beautiful, so musical.”

Plummer, a professor of science education, began birding in 2013. Soon after she started going on early morning walks at Penn State’s Shaver’s Creek Environmental Center during migration season, she was hooked. Particularly by the variety of birdsong. “Someone would say, ‘Oh, there’s a black-throated green warbler singing,’ and I’m like, ‘I can’t even pick that out.’ I just got more and more interested in identifying bird calls and birdsong,” she says.

Plummer downloaded a couple of apps on her phone and bought a simple handheld audio recorder to take with her on her walks. That was in 2014; a decade later, she has recorded the songs of close to 400 birds (she eventually upgraded to a more sophisticated recording system) and she can identify around 200 of those by ear while out in the field. She tracks her observations on eBird, a site managed by the Cornell Lab of Ornithology, which houses more than 100 million bird sightings contributed by birders all over the world.

Being that her passion is birdsong, she opts for more quiet, less frequented spaces where she hopes to record birds she’s never heard before or that she hasn’t recorded very often. There are plenty of birdsongs and calls that Plummer hasn’t yet heard and so many she still wants to hear. But top of her list is the call of the American goshawk—an extremely rare species of hawk she has yet to encounter.