Julia Flynn Siler

Dr. Nilo Merino Recalde, a young researcher studying birdsong at the University of Oxford, walks through a wintry landscape leading into Wytham Woods in Oxfordshire, a woodland habitat for birds, foxes, badgers, and insects. This 1,000-acre woodlands, which date back to the last ice age, are one of the most studied wild places on the planet.

Over the past three years, Nilo has been part of a team of researchers at Oxford who’ve recorded over 20,000 hours of birdsong. Most of the songs are made by the woodland’s population of great tits (Parus major) which make distinct, two-syllable phrases in variations that sound like “tea-cher, tea-cher.” Some of the songs come from its close cousin, the blue tits (Cyanistes caeruleus) which makes trilling songs like “tsee-tsee-tsee-di-di.”

 

 

Nilo drove his ancient VW van to meet me in the parking lot of the woods, which is part-way up a hill. I’ve ridden – and partly walked – my clunker of a bike up it but managed to arrive just before our arranged meeting time, slightly out-of-breath and damp with sweat from the exertion. It is bitterly cold and while the trees are still bare, the first daffodils are starting to bloom in the woods, promising warmer days ahead.

We walk up a gently sloping hill together, covering about half a mile along a wide dirt path. In the spring, this will all be covered with wildflowers, he tells me, gesturing towards the meadows, but for now, the open fields are filled with mud and dried grass beneath a dense grey sky. A pair of sheep munch away behind a fence and ignore us as we walk by. As we approach to the woods, I can hear the muffled traffic sounds of the nearby A34 roadway but very few birds.

I’d read of the place we were walking, Wytham Woods,  in The Way Through the Woods, a novel by the late British crime writer Colin Dexter first published in 1992. The plot involves the disappearance of a young Swedish student in Oxfordshire. It’s hard to miss traces of Dexter’s invention, Inspector Morse, throughout Oxford. My local pub, The King’s Arms, has a framed black and white photo of the actors who played Morse and his sidekick, Sergeant Lewis, near the entrance.

On this blustery spring morning, we enter the protected woodlands and reach a cylindrical small birdhouse hanging from a tree. Nilo unlatches and swings open its little door to check if there’s an inhabitant inside. Bats who discover these birdhouses often hang upside down in them, displacing what otherwise would be the nesting tits inside. This one has the dried remnants of leftover moss from an old nest from last year, though some birds have already started to bring new moss into some of the thousand birdhouses hung throughout the woods.

Scientists have studied the Great Tit population in these woods for nearly 78 years, since 1947, just two years after the end of World War II. Over that time, they’ve answered questions such as do birds age? What determines when they lay their eggs and how many they lay? How do they select their mates, and do they remain faithful to them? (The Wytham Tit Project has an excellent web site explaining these research areas and much more.)

Nilo and his team applied a new approach to studying these birds – they trained an AI model to recognize the individual bird songs they’d recorded and to measure the differences in songs between individuals. The program allowed them to track variations in song repertoires in a bird population and trace patterns in song evolution.

 

 

Using this technology, they tracked how songs evolved over time with the arrival and departure of individual birds. One key finding: the pace of song evolutions within neighborhoods was driven by individual birds coming and going with older birds conserving the “homegrown” songs. Newcomers tend to adapt by learning the shared songs of the community, but they also increase the diversity of the shared songs because they tend to learn more songs overall. As the study’s authors write, they enrich the local “musical scene.”

“Just as human communities develop distinct dialects and musical traditions, some birds also have local song cultures that evolve over time,” Nilo wrote around the time of his team’s publication of its study this month in the journal Current Biology. “Our study shows exactly how population dynamics – the comings and goings of individual birds – affect this cultural learning process, influencing both song diversity and the pace of change.”

We walk back down the hill, past other researchers laying out long white string to mark off portions of the ground. We were far away from the woods’ 10,000-year-old peat-based Marley fen, so the measuring may have been part of an ongoing climate change project that has been collecting data for the last two decades. I had hoped we might see a badger or two – since I’d watched a video of those strange, smelly carnivores and the charming scientists who study them in preparation for my visit to the woods. Nilo later invited me to the badger watching sessions that the staff organizes once the animals become more active, usually around May.

As we near the end of our walk, Nilo and I reflect on how lucky both of us were to spend time in a place like Wytham Woods and the University of Oxford. Nilo is a Postdoctoral Researcher with the Department of Biology, working with the Edward Grey Institute of Field Ornithology. I’m an academic visitor at the University here for six months, studying with its Centre for Life-Writing.

Together for just an hour or so in this much-studied 1,000-acres, we both knew how lucky we were to have found safe and comfortable homes – however temporary it might be – within the university ecosystem. Amidst the alarming headlines of the past few months, we both felt lucky to be walking through the woods on that wintry day, listening for birdsong.

 

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Julia Flynn Siler, an academic visitor at the Oxford Next Horizons Program, comes from a family of devoted birders. Follow her series of essays from Oxford and elsewhere on Substack.