Anne Charmantier: Studying Titmice

As a child, Anne Charmantier dreamed of working with whales and polar bears. As the daughter of “early environmentalists”—both Professors the University of Marseille—she had chosen the right career path. Except that she ended up studying chickadees instead. Ever since her university studies in evolutionary ecology, passerines have been a constant in her life. During her master’s program, she contributed to the long-term study of blue and coal tits, launched in 1976 in southern France and Corsica. Today, as the director of research in evolutionary genetics at CEFE, she is in charge of this program. With a radiant glow from a field trip to Corsica she had just returned from the day before, she saysshe “appreciates the importance and responsibility of continuing this monitoring work across five sites, which involves seven permanent researchers and about twenty field staff each year.”

A recipient of this year’s CNRS Silver Medal, she quotes Newton:“If I have seen further, it is because I have stood on the shoulders of giants.” One of her own giants is Jacques Blondel, a leading ecologist and pioneer of the evolutionary ecology approach, who launched the chickadee research program a year before she was born. Anne Charmantier doesn’t boast about this silver medal: “I regret this personalization of the award. I love research because it involves asking questions together and because I can rely on collaborations to find the answers.” ” And the researcher makes sure that her profile will indeed highlight her many collaborations. She describes the “Journal Clubs” she regularly organizes with colleagues and students. During these coffee-and-reading sessions centered on a recent scientific publication, everyone shares their thoughts and discusses the new findings.

Infidelity Among Chickadees

As early as her doctoral thesis, Anne Charmantier obtained unexpected results, notably discovering that chickadees are unfaithful. By studying the genomes of broods, she found that in many nests, at least one chick has a biological father different from the social father who raises it. A finding that contradicts this bird’s monogamous behavior—at least its social life as observed in gardens, where chickadees form pairs and share the tasks of nest-building and feeding the young.“I wondered why these females are unfaithful, mating with other males, usually nearby. Do they choose them based on specific criteria, on traits that their partner lacks?” This hypothesis of “good genes” that are important for the species—which individuals would identify and prioritize in their reproductive behavior—has not ultimately been confirmed. But the inclusion of evolutionary genetics in the chickadee research program is well underway.

Her specialization in quantitative genetics led to her being hired by the CNRS in 2006 at the age of just 29.“Thanks to a Marie Curie fellowship during my PhD, I was welcomed at the University of Edinburgh by Loeske Kruuk, a specialist in quantitative genetics applied to wildlife. It was a new field in France, as in the early 2000s this discipline was limited to agricultural genetic selection. ” Her collaboration with her British mentor continued until the 2014 publication of a book on the contribution of quantitative genetics to evolutionary ecology. Using this approach, Anne Charmantier has pursued two major lines of research: studying how passerines adapt to climate change and how they evolve in urban environments.

Early-arriving chickadees

One of her major findings concerns how reproduction adapts to global warming. Chickadees lay their eggs earlier in warmer years, in response to the need to feed their young with juicy caterpillars that become available right after the trees bud. Missing the season puts the chicks’ survival at risk.  “If chickadees fail to detect the early arrival of spring, it will be a disaster for the broods,” explains the researcher. Through her genetic study of chickadee populations—conducted “using tiny blood samples; a non-invasive 10-microliter blood draw from the neck”— she confirms that early egg-laying, as well as plasticity—that is, the ability to adapt the egg-laying date to spring signals—are passed down from one generation to the next through the bird’s genetic makeup. And evolution favors these two traits in chickadees. Natural selection favoring early-laying chickadees is even strongly accentuated—by about 40%—during a spring heat wave, the scientist explains.

More recently, Anne Charmantier has also turned her attention to how chickadees adapt to urban environments.“More out of necessity than a desire to give up my fieldwork in the great outdoors. But two young children and health issues led me to start installing nest boxes in the city,” the researcher confides, glancing at a photo of a Corsican mountain range displayed in her office. Together with two colleagues from CEFE, Arnaud Grégoire and Marcel Lambrechts, she has ultimately become passionate about this research, even though urban chickadees differ from their forest counterparts in many ways.

“A community garden where we raise young chickadees”

Their research shows that these birds are smaller, duller in color, lay fewer eggs, are more aggressive, but also more exploratory. To determine whether these traits are acquired or not, the team set upa “shared nursery”at the Lunaret Zoo,where they raise young chickadees hatched from eggs collected both in the city and in the forest. There is indeed a genetic transmission of the observed traits, because even though all the chicks are raised under the same conditions, they retain certain traits associated with their environment.” The researcher goes on to explain the scale of the task:“It’s a time-consuming project because we have to feed the chicks continuously from 7 a.m. to 9 p.m. every day for three months!”

In 2023, Anne Charmantier secured an ANR grant of nearly 700,000 euros to study the interactive effects of urbanization and climate change, as part of the Acacia project.“For example, city chickadees are exposed to urban heat islands. Studying them can help us understand how—or whether—they adapt to warming,” she explains. She is conducting this study in collaboration with her colleague Samuel Caro, a specialist in avian ecophysiology, with whom she will specifically test the birds’ thermoregulatory capabilities. And as if that weren’t enough, the researcher has embarked on an educational project in partnership with Lirdef (Interdisciplinary Laboratory for Research in Didactics, Education, and Training). She’s now setting up nest boxes equipped with cameras in several schools in Montpellier and Paris to allow children to follow the lives of chickadees in the schoolyard.“The idea is to test whether learning biology by treating the chickadee as a subject rather than an object helps develop a different relationship with nature,” explains the tireless researcher. Results will be available at the end of the school year.