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Timing of bird migration under climate change: phenotypic plasticity, microevolutionary response or both?

Final Report Summary - BIRDCLIMCHANGE (Timing of bird migration under climate change: phenotypic plasticity, microevolutionary response or both?)

The BIRDCLIMCHANGE project was granted to Luis Cadahía Lorenzo in the call FP7-PEOPLE-2009-IEF and it was carried out between 1 May 2011 and 30 April 2013 at the Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo (Norway), under the supervision of Prof. Nils Christian Stenseth.

The main goal of the BIRDCLIMCHANGE project was to understand how migratory bird species adapt to current climate change. To achieve this, the project was divided into two specific objectives: first, to identify phenotypic traits related to migration phenology that showed changes as a consequence of climatic alterations and, second, to study the inheritance patterns of those traits, to find out whether their modification is in accordance with microevolutionary processes or phenotypic plasticity patterns.

The analyses carried out to achieve these goals were performed with data from a pied flycatcher population from southern Norway, a migratory passerine bird presumed to winter in tropical West Africa. The beginning of the project entailed a good deal of compiling, organising and formatting data. The next stage entailed getting acquainted with the different climatic databases available in order to gather the climatic parameters that, first, best reflect how climate change has happened in the almost last three decades and, second, influence migratory birds at the different stages of their annual life cycle. Migratory birds' vulnerability to climatic alterations is high because of two intertwined factors: first, they spend different parts of the year in areas that are thousands of kilometres apart and, second, the rate and direction of climate change are not consistent across those areas. To capture this variability, we performed analyses with both direct measurements (e.g. temperature, precipitation, wind) and climatic indices (e.g. NAO, normalised difference vegetation index (NDVI)) from wintering areas in West Africa, migratory flyways from North Africa and Europe, and breeding grounds in Norway.

Our main findings show that there has been a significant advancement in migratory phenology, with flycatchers arriving at their breeding grounds in Norway over four days earlier than they used to almost 30 years ago. In general, males arrive, on average, six days before females, and, within each sex, adults arrive before juveniles, although migration phenology has advanced at a similar rate in all of them. The analysis of the climatic influence revealed that the advancement in migration phenology occurred as a result of a trade-off between, on the one hand, climatic changes in the wintering areas and migratory journey and, on the other hand, conditions at the breeding grounds. High primary production (corresponding to a high NDVI index, a proxy for food abundance) in West Africa showed a positive relationship with arrival in Norway. This means that, if only dependent on this, flycatchers would arrive later in years with high food availability in Africa, probably because of delayed departure from their wintering quarters. A similar effect was observed when studying primary production in North Africa and southern Europe. In this case, our results are consistent with the likely existence of stopovers in these areas, which would delay arrival in Norway in years with abundant food. A fact further supporting this is that wind direction and strength when crossing the Strait of Gibraltar, which could potentially delay or speed up migration, have not proved to influence arrival in Scandinavia. On the other hand, the relationships between conditions at the breeding grounds and arrival date show a negative direction. Birds arrived earlier in warmer and rainier years. In southern Norway, low-pressure systems that bring rain to the area also entail the existence of higher temperatures and southern winds that will act as tail-winds for the flycatchers, facilitating the last stage of their migratory journey. These results highlight that not only arrival at the breeding grounds is influenced by conditions at the areas birds cover throughout the year, but also that this influence can have different signs and generate opposite patterns. This causes the advancement in arrival date to arise as a compromise between those opposite effects. As a consequence, migratory birds' vulnerability to climate change is increased, because these diverse impacts from different areas may cause arrival to be mismatched with the conditions at the breeding grounds, having potentially negative effects when it comes to survival and fitness of individuals, which will, in turn, have an impact on the persistence of populations. This can already be observed by the advanced breeding phenology we have also detected in our population, whose causes (climate at the breeding grounds, migration phenology, food availability, population density, etc.) and potential consequences are being investigated at present.

A key point to be able to perform the analyses necessary to study climate change influence in migration phenology has been the training activities included in the project. These started by establishing collaborations with colleagues at CEES and continued, in a more formal way, by attending a course on 'Advanced Statistics for Biologists using R' at the University of Sheffield (United Kingdom (UK)), with Andrew Beckerman and Dylan Childs. The training activities have been especially relevant for the inheritance analyses pertaining to the second objective of the project. I took one short, introductory course at the University of Liège (Belgium) and a two-week intensive course on Quantitative Genetics at the University of Uppsala (Sweden), with leading researchers in the field Bruce Walsh and Bill Muir. Here I got acquainted with the necessary theory and application of these methods to my particular research problem of studying inheritance patterns in migration phenology traits. Because of the initial delay in the project caused by the longer-than-expected effort to organise and compile data, the second objective could not be accomplished within the timeframe of the proposed investigation. However, preliminary pedigree analyses have already started and expected collaboration with Dr Jane Reid (University of Aberdeen, UK), an expert in the field, will ensure its successful accomplishment.

Several scientific publications are being prepared in connection with the BIRDCLIMCHANGE project. One scientific paper entitled 'Climate change at different locations drives advancement of migratory spring phenology in a passerine bird' is at a final stage and is to be submitted in the near future to a high rated journal. In addition, the analyses on the factors influencing earlier breeding phenology are already underway and a publication describing the results is currently in preparation. Regarding participation in conferences, our project was presented in advance at the Joint Synthesis Centre Post-doctoral Symposium at the NESCent - Duke University, Durham (North Carolina, United States (US)) in April 2011, and our results on migration phenology were presented at the conference Phenology 2012 - Future Climate and the Living Earth at the University of Milwaukee (Wisconsin, US) in September 2012. Furthermore, since the research we carried out aims at understanding the effects of climate change, our results can be very relevant to inform conservation policies in the context of the European Union (EU).

Finally, with regards to career development, I have already applied for funding to continue the research on adaptive mechanisms to climate change in migratory birds and expand this to investigating how these mechanisms determine population dynamics. Thanks to the EU funding for the BIRDCLIMCHANGE project, I have established connections with other researchers in Norway (University of Tromsø, NINA and NTNU - University of Trondheim) and abroad (universities of Aberdeen and Groningen), with the aim of creating an international collaboration network to study the impact of climate change that will greatly benefit my career.

Contact details:
Luis Cadahía Lorenzo
Centre for Ecological and Evolutionary Synthesis (CEES)
Department of Biology - University of Oslo
P.O. Box 1066
Blindern, N-0316 Oslo, Norway
Tel: +47-467-96175
Email: luis.cadahia@gmail.com and luis.cadahia@ibv.uio.no