Explaining and Predicting the Migration and Phenology of Europe-African Migratory Birds

Lead Research Organisation: British Trust for Ornithology
Department Name: British Trust for Ornithology (Norfolk)


The migration of birds from temperate and arctic breeding grounds to lower latitudes for the non-breeding season is a major global wildlife event, comprising billions of birds and providing an important component of global ecosystems. Some of these movements are truly amazing - some 12 gram birds fly 3000km non-stop to reach their non-breeding grounds. The majority of inter-continental terrestrial migrations are undertaken by songbirds, which migrate across broad fronts, often stopping to refuel on their journey. Despite intensive study on the breeding grounds, and to a lesser extent the non-breeding grounds and stop-over sites, research to simulate the migratory journeys themselves, or to test theoretic models of migration for such species, is rare. A generic model of migration has never been applied to songbirds undertaking the Europe- trans-Saharan migration; this is a major objective of this proposal. In light of projections of climate and land-use changes on the breeding, non-breeding and stop-over grounds of these species, such models are urgently required. Migrants could be especially vulnerable to climate change given their reliance on the linkage between widely-separated areas, which are potentially undergoing very different changes.

The main limitation to developing and testing models of songbird migration has been an inability to monitor individual movements so as to understand their routes and strategies. The recent development of geolocator trackers, which record time and location and can be used on the smaller species that comprise the majority of migrants, has provided data to test migration models for the first time. Here, we will collate tracking, and extensive ringing and observation data for trans-Saharan migrants, to better understand their migratory routes and decisions. Simultaneously, we will develop flight models for individual species, which consider species-specific physiology and form to determine their flight-range potential. We will use the outputs in spatially-explicit dynamic programming (DP) models, and will test their ability to replicate observed patterns of migration. This will build on earlier work modelling optimal migration using very simple systems.

We have already developed pilot flight range models that replicate well the timing and routes of migration of tracked individuals of species with near-linear migrations. Building on these data, we will use DP models, with realistic landscape resources/costs, to evaluate optimal migratory routes and refuelling locations given temporally-constrained destination rewards (i.e., likely breeding success). We will consider landscapes with dynamic resource availability, based on factors such as species-specific habitat preferences and likely food availability (based on weather and NDVI), and will include factors such as wind direction, location (relative to time of year) and an individual's energy stores to determine whether they should stay or, if not, where they should move to. We will use these models to explore inter-annual variation in arrival dates at migratory end-points, to aid understanding of what drives phenological changes in migratory species, and to test theories of what determines migratory decisions.

Modelling formalises our understanding of migration, making explicit our assumptions and any gaps in available data. Crucially, it can also inform our understanding of the migratory process and how that process will be influenced by future environmental changes. The end product will be a much better understanding of the drivers of the routes and strategies of long-distance migrants, and a modelling framework that can be applied to a wide suite of migratory passerines in different regions, or under scenarios of climate and land-use change, to simulate consequences for migratory journeys.

Planned Impact

The project will result in 3 junior researchers with exceptional experience in analytical and computational modelling at the forefront of ecology. This will deliver key skills among those identified by NERC as 'most wanted' in the environmental sector, including modelling, data management and numeracy. In addition, the project will initiate a large network of researchers across Europe, with complementary interests in mapping, modelling and understanding the migratory process. UK scientists will be at the heart of that network. Both of these aspects will strengthen the UK's science base.

We anticipate a wide range of academic beneficiaries, including ornithologists, conservation biologists, migration ecologists, behavioural ecologists and those working at the interface of ecology and technology. These fields will be advanced by making a step change in the availability of data to understand and model migration, the knowledge required to move the field forward, and awareness of the potential and current limitations of tracking technology. See further details in 'Academic beneficiaries'.

Beyond academia, beneficiaries include (i) conservation policy makers, (ii) citizen scientists, and (iii) the wider public. In respect of (i), our past work has been influential in shaping global conservation policies. For example, it has been presented at the CBD-COP in Nagoya, 2010; in strategy documents for a side-event at the CBD-SBSTTA in Montreal, 2012; and at the IPCC Paris 2016 meeting. SGW's development of a climate change indicator was adopted by the EU as a key biodiversity & climate change indicator, and hence a barometer of environmental health. An updated version of this (with PAS) has also been adopted as one of the CBD's Aichi 2011-2020 target metrics and is included in the CBD decision X1/3. European modelling work, published in Sanderson et al. (2016), was cited as being instrumental in helping to retain the current EU habitats directive legislation in its current format. We anticipate that the current project could yield equally influential outputs, with implications for policy on protected areas, climate change adaptation and hunting regulations. Stakeholders relevant to these issues include JNCC, Euro. Environment Agency, IUCN, IPCC, UNEP, Convention on Biological Diversity and BirdLife International.

(ii) Citizen scientists are pivotal to collecting fundamental data - especially the bird-ringing and resighting data - on which this project depends. Ample evidence suggests that citizen scientists are more engaged when they are aware of the value and consequences of their efforts. We anticipate, therefore, that the results of our project will be of high interest to the tens of thousands of concerned individuals across Europe and Africa who have contributed to the data sets that we will utilise.

(iii) The wider public will benefit from this research both directly, from the point of view of interest and engagement, and indirectly, through our increased capacity to advise policy to prevent biodiversity loss. From a societal perspective, migratory species have great cultural value in all countries in which they occur, tending, as they do, to mark a change in seasons. Hence, an important impact of this research will be to disseminate findings to the wider public, and to ensure the findings are communicated to policy-makers who represent the public. The economic impacts of most migratory species have yet to be fully, or even partially, understood but, as migrants comprise many important insectivores and frugivores, changes to their populations could have major ramifications for agriculture, forestry and carbon fixation, as well as economic activities associated with wildlife cultural services (particularly nature viewing). Consequently, a major task will be to raise awareness of potential changes to these species to as wide a group of stakeholders as possible, to realise the benefits of this research to the wider public.


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