Paul Dufour spotting and counting large groups of shorebirds that overwinter and migrate through the bay of Dakhla in the Western Sahara (photo credit: Boris Delahaie).
Institution: Laboratoire d’Ecologie Alpine – Grenoble, France
Current academic life stage: PhD
Research interests: Understanding the evolution of migration behavior in birds and its ecological and evolutionary consequences.
Current study system: I am interested in the whole avian class, but I am also studying more specifically the order Charadriiformes, which shows quite exceptional and diverse migration strategies. Also, I have recently started studying populations of Richard’s Pipit in Europe, a species of Asian passerine that normally overwinters in Southeast Asia, which we suspect uses a new migration route towards Western Europe.
Recent paper in Journal of Biogeography: Dufour P, Descamps S, Chantepie S, Renaud J, Guéguen M, Schiffers K, Thuiller W, Lavergne S. 2020. Reconstructing the geographic and climatic origins of long‐distance bird migrations. Journal of Biogeography 47: 155– 166. DOI: 10.1111/jbi.13700. FREE ACCESS for 2020 & 2021
Motivation for the paper: There are still many unanswered questions around biogeographic scenarios that could explain the emergence and evolution of seasonal migration—in particular large geographic migration—in birds. As previous studies on smaller families or clades have shown rather diverse results, we wanted to test whether general evolutionary patterns could be described for large clades of migratory birds. At the same time, we wanted to examine how these evolutionary patterns could be related to the tracking of climatic niches during different seasons.
(A) A group of Brent Geese (Branta bernicla hrota) just returning from their wintering grounds, photographed in Longyearbyen (Svalbard, Norway) when Paul was working on seabird colonies. (B) A Woodchat Shrike (Lanius senator), probably on its way to its breeding grounds, looking for insects on a garbage mound in the middle of the Western Sahara.
Key methodologies: Since our aim was to understand the biogeographic and climatic context for the evolutionary emergence of seasonal migration at global scale, we first manually coded the migration strategies for all current species of birds. While many distribution maps reflect the migration strategy (i.e. strict migratory species), this is not the case for resident or partially migratory species, for which it is necessary to look precisely at the available information in reference handbooks. Similarly, compared to what has been done in the past, we wanted to address the issue of niche tracking between season, in particular through a measurement of climatic overlap, on all extant bird species to study global patterns of these metrics. We also wanted to place this question in an evolutionary context by using phylogenetic regressions.
Unexpected challenges: Describing the niche of a species often requires consideration of the climatic and environmental variables to be taken into account. In the case of our study, we had to make a choice between being able to consider the avian class as a whole and using more variables to define the niche of the species. Since a significant proportion of species overwinter over marine areas, we chose the first option but had to rely on temperature alone to define climatic niches, finding no other variables related to our biological assumptions and available over land and ocean. We believe that addressing this issue by comparing all these different migration strategies at global scale is an interesting approach and that this simplification is acceptable as temperature has been shown to be a good proxy in the distribution of bird species.
Major result and contribution to the field: We found that migratory species, and even more so long-distance migratory species, generally experience a warmer climate on their wintering grounds than on their breeding grounds, although there are notable exceptions. We also confirmed that seasonal migration is a labile trait that has appeared and disappeared at different periods in the history of several avian lineages. As a consequence, we have not reported dominant biogeographic scenarios (i.e., both temperate and tropical ancestors) that could have explained the evolution of migratory behaviour in the major migratory orders. Interestingly, we found an ancestral migratory behaviour deeply rooted in the history of the great radiation of the Passeriformes that could coincide with the great expansion of this clade.
What are the next steps? This last result calls for further analysis of the potential role of migration behaviour in diversification processes. The richness of large groups of migratory birds suggests that migration might be a driver of speciation. Similarly, different migratory species show different strategies or year-round niche tracking: the fact that both short- and long-distance migrants showed lower thermal overlap values than variable‐distance migrants opens up interesting approaches to study the evolution of migration. A first idea might be to test whether migratory birds do not migrate ‘too’ far compare to their optimal climatic niche and to link this result with the progressive shift of breeding and wintering areas.
If you could study any organism on Earth, what would it be and why? There are hundreds of birds that I would like to study (seeing them would be very enjoyable in itself) because their migration strategies are so extraordinary and open the door to a multitude of questions. However, at the moment I am happy to be able to study Richard’s Pipit, an Asian passerine species whose appearance in Europe remains enigmatic. If our hypotheses are correct, we may have the chance to observe really drastic changes in migration routes in a very short period of time.