Anne Charmantier: charcoal on chickadees

In charge of a long-term study program on chickadees, Anne Charmantier is interested in the adaptation of these passerines to climate change and the urban environment. Director of research in evolutionary ecology at CEFE, she is a 2024 CNRS silver medalist.

As a child, Anne Charmantier dreamed of working on whales and polar bears. As the daughter of "early environmentalists", both of whom were teacher-researchers at the UM, she made no mistake about her vocation. Except that she ended up working on chickadees. Ever since her university studies in evolutionary ecology, she's been fascinated by passerines. As part of her post-graduate studies, she contributed to a long-term study program on blue and great tits, launched in 1976 in southern France and Corsica. Today, she is in charge of this program, having become Director of Research in Evolutionary Genetics at CEFE. With a radiant face earned during a field trip to Corsica, which she left the day before, she says she " appreciates the importance and responsibility of continuing this monitoring work on five sites, which mobilizes seven permanent researchers and around twenty people in the field each year ".

This year's CNRS silver medallist, she quotes Newton: " If I've seen so far, it's because I've stood on the shoulders of giants ". One of her giants is Jacques Blondel, the great ecologist who pioneered the evolutionary ecology approach and launched the chickadee program a year before she was born. Anne Charmantier isn't proud of her silver medal: " I regret this personification of the prize. If I like research, it's because we ask questions together, and I can rely on collaborations to find the answers. And the researcher goes on to say that her portrait will feature her many collaborations. She recounts the "Journal Club" she regularly organizes with colleagues and students. During these café-lectures on a recent scientific publication, everyone shares their thoughts and discusses new findings.

Unfaithful chickadees

Anne Charmantier's doctoral thesis yielded unexpected results, including the discovery of the infidelity of chickadees. By studying the genome of broods, she discovered that, in many nests, at least one young bird had a different biological father from the social father who raised it. A result that contradicts the monogamous behavior of this bird, or at least its social life observed in gardens where chickadees are in pairs and share the tasks of making the nest and feeding the young. " I wondered why females are so unfaithful, mating with other males, usually nearby. Do they choose them based on precise criteria, on traits that their partner doesn't possess? " This hypothesis of "good genes" important to the species, which individuals would identify and favor in their reproductive practices, was ultimately not confirmed. But evolutionary genetics is now well and truly at the forefront of the chickadee program.

Her specialization in quantitative genetics earned her a position at the CNRS in 2006, aged just 29. " Thanks to a Marie Curie grant during my thesis, I was welcomed to the University of Edinburgh by Loeske Kruuk, a specialist in quantitative genetics applied to wild species. This was a new specialty in France, as in the early 2000s this discipline was reserved for agronomic genetic selection. " The collaboration with her British mentor continued until the publication in 2014 of a book on the contribution of quantitative genetics to evolutionary ecology. With this approach, Anne Charmantier will nurture two major lines of research: studying how passerines adapt to climate change and how they evolve in urban environments.

Early titmice

One of his major findings concerns the adaptation of reproduction to global warming. Chickadees lay their eggs earlier in warmer years, responding to the need to feed their young with juicy caterpillars that are available just after the trees have budded. Missing the season means jeopardizing the survival of the chicks. " If the chickadees don't catch the early spring, it will be a catastrophe for the broods ", explains the researcher. Thanks to the genetic study of chickadee populations, which the researcher carries out "using minute blood samples; a non-invasive 10 microliter blood sample taken from the neck", she confirms that not only early egg-laying but also plasticity - in other words, the ability to adapt the date of egg-laying to spring signals - are transmitted from one generation to the next by the bird's genetic heritage. And evolution favors these two traits in chickadees. Natural selection in favour of early chickadees is even strongly accentuated, by around 40%, during a spring heat wave, explains the scientist.

More recently, Anne Charmantier has also turned her attention to adapting chickadees to the urban environment. " More out of necessity than out of a desire to give up all my land in the wild. But two young children and health problems prompted me to come and install nesting boxes in town ", confides the researcher, squinting at the photo of a Corsican massif on display in her office. Along with two CEFE colleagues, Arnaud Grégoire and Marcel Lambrechts, she has finally developed a passion for this research, despite the fact that urban chickadees differ from their forest counterparts in many respects.

"A communal garden where young chickadees are raised".

Their work shows that the individuals are smaller, duller, lay fewer eggs, are more aggressive but also more exploratory. To understand whether or not these traits are acquired, the team launched a project in the Lunaret zoo nursery, " a shared garden where young chickadees born from eggs collected both in the city and in the forest are raised. There is indeed a genetic transmission of the characteristics observed, because if all the young are raised in the same conditions, they retain certain characteristics 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 7am to 9pm every day for three months!

In 2023, Anne Charmantier won an ANR grant of nearly 700,000 euros to investigate the interactive effects of urbanization and climate change, the Acacia project. " For example, urban chickadees are subject to urban heat islands. Studying them can help us understand how they adapt - or not - to global warming," she explains. A study she is conducting in collaboration with her colleague Samuel Caro, a specialist in bird eco-physiology, with whom she will be testing their thermoregulatory capacities. As if that weren't enough, the researcher has also embarked on an educational project in partnership with Lirdef (Laboratoire interdisciplinaire de recherche en didactique, éducation et formation). Here she is, installing nesting boxes with on-board cameras in several schools in Montpellier and Paris to enable children to follow the life of tits in the playground. " The idea is to test whether learning about biology through the chickadee as a subject rather than as an object can help develop a different relationship with nature ", explains the inveterate photographer. Results at the end of the school year.