Animal Tracking Technology

Bird migration is changing in response to global environmental change. Winters are getting warmer, the human population is growing and with that, generating more organic waste.

Some birds feed on our discarded food all year round and no longer migrate, whilst others, from the same species, living in the same locations still migrate. The big challenge is to understand the drivers behind these different individual responses to global environmental change. UEA Researcher Aldina Franco joined forces with British Trust for Ornithology and the University of Porto to develop ground-breaking technology to try to unravel the mystery. Across Europe and in Southern Europe in particular, many bird species (e.g. white storks, common quails, house martins, barn swallows, hoopoes) that used to be migratory and were spending the winter in Africa, now have some individuals that do not migrate.

The causes are not fully clear but are thought to include factors such as climatic change and winter food availability. Scientists are tracking white storks (adults and their offspring) to understand why they have changed their migratory behaviour and this links back to climate change and the storks’ feeding habits. The project has shown that since the mid-’80s an increasing number of white storks have chosen to stay in Iberia all year round rather than migrate to Africa in the winter. The findings reveal the stork’s movements between roosting, nesting and feeding areas; showing a variety of strategies across different birds, some favouring long distances flights, others short. Some spend most of their time at landfill sites feeding on “junk food” while others do not use these sites. Which is the best strategy? Which are the birds that are more successful? New results have actually showed that storks that feed on “junk food” are in better condition and live longer.

Innovative Technology

In partnership with The British Trust for Ornithology (BTO), and the University of Porto, UEA Researcher Aldina Franco created the Movetech Telemetry project to develop ground-breaking technology in the form of GPS/GSM trackers. One of the big advantages of these trackers is that they do not need to be recovered to retrieve data, the tracker records the positions of the storks and sends the data remotely via the mobile phone network. The data is sent to an animal movement data repository and can be made available to members of the public. These are solar powered tracking devices with an on-board accelerometer and temperature sensor similar to a smartwatch; can track the animals eating habits and activity patterns every 20 minutes for several years. The Movetech Telemetry tracking technology used on the storks was developed further, now offering a wide range of sizes and weights (between 18g – 60g) that can be used on a variety of animal species (birds, mammals, and reptiles).

The white stork is an ideal species for this research, it is a large migratory bird, weighing up to 4.5kg, so they can carry a bigger battery that lasts longer. Storks are long-living birds, the average lifespan is 12 years - 25 years in the wild so it is interesting to see how they adapt to environmental changes throughout its lifespan. The trackers are less than 3% of the weight of the storks and have a weak link thus, on average, after a couple of years, they fall off from the storks’ back, causing little to no impact to their lives.

This study was conducted in the South of Portugal where landfill sites will gradually stop receiving organic waste, but composted instead. These tracking devices will enable researchers to understand how the storks will respond to these new environmental changes. Some may well go back to migrating to sub-Saharan Africa during the winter.

The landfill resident storks had access to food all year round, and were quite attached to the sites – imagine having a free restaurant at your doorstep for the rest of your life! The research showed that some storks are stationary at the landfill sites, waiting for the rubbish trucks to arrive for up to 2 hours, feeding then going back to the nest. However, not all white storks use landfill sites all year round, or even as often as others, demonstrating an interesting choice to ignore a surely most convenient source of food?

In nature, white storks usually feast on wild crayfish and grasshoppers, they are opportunistic and feed on the most abundant resources in the environment which can include small animals and fish. Some of the landfill residents seemed to prefer to eat “junk food” even though there was other natural food available.

Dr Aldina Franco, from UEA’s school of environmental sciences, is leading the project. She said:

Storks used to be a declining species in Europe and had to be reintroduced in some countries (Switzerland and Sweden for example). Contrasting with so many species that are declining due to the human transformation of the landscape, pollution and climate change, it is refreshing to see the white storks doing well.

What are we doing?

Using the data captured by the tracking devices that is being transmitted every day via GSM, Aldina and her colleagues can track the white storks’ movements, mortality rates and foraging habits right from their offices at UEA and Porto. They are able to follow their migration movements that open up a different understanding of how these animals migrate, what routes they take and how they overcome barriers, for example crossing mountains or being faced with storms in the desert. Additionally scientists are able to identify areas where they are disappearing to better understand the causes and locations where the birds suffer most mortality. This way they’re able to start uncovering some mysteries around migration.

For instance, why do some birds go to the coast of Africa, whilst others migrate to the inner part of Africa, and what prompts them to go in different directions?

This year (2019), researchers captured 50 adult storks as part of a project funded by the Foundation for Science and Technology in Portugal (Birds on the Move Project), and developed with colleagues at the University of Lisbon and Porto. Aldina and her colleagues are tracking the offspring of these storks to understand if they’re following their parent’s footsteps.

What did we find?

Some storks that nest in Portugal stay there all year, others move around in Iberia, and others migrate to sub-Saharan Africa for the winter. One stork was captured in Portugal in the winter but went to Germany in the spring. In the past, the German storks would migrate to Africa, now some winter in Portugal.

Interestingly, the offspring of resident parents didn’t seem to follow their parents’ strategies. All Portuguese young storks migrated to sub-Saharan Africa for the winter. At this time of the year, the rain is receding in the Sahel so it’s dry, there are plenty of grasshoppers, and low vegetation cover where the storks can walk across in search of food.

The mystery continues

Despite many advances in understanding the question as to why some birds are migratory and others are residents remains and Aldina, colleagues and PhD students still have many questions unanswered and will continue to research: what part global change plays in facilitating different migratory strategies. These particular storks are interesting as they are influenced by several factors: landfill site “junk food” and climate change. The climate is better for their prey, but the landfill sites are also a convenient source of food. It is still not clear why the offspring of parents that use landfill sites all year seem to be completely migratory, unlike their parents. Aldina’s UEA PhD students are trying to understand just this as well as how the weather may influence the migratory decisions of birds. To get further insight, they will need to track these birds in the long-term and observe how birds respond to future change in the environment.

Storks on a rubbish tip

Tracking in practice

The tracking devices are currently being used in The White Stork Project in the UK. White storks were once a native bird of Britain, however, through time, they started to disappear. It is thought that these sociable birds failed to survive in Britain due to habitat loss, over-hunting and targeted persecution. The project aims to re-introduce them to Britain with the core area around the Knepp Estate in West Sussex. In collaboration with the Durrell Wildlife Conservation Trust and Cotswold Wildlife Park, white storks were transported over from Poland’s Warsaw Zoo. These birds could no longer fly but were still able to breed. They were bred in the UK and released in the Knepp Estate. The Movetech Telemetry GSM trackers were deployed on these birds so that their movements could be tracked and their migration could be followed. The routes they’re taking are already surprising researchers; many explored Britain’s south coasts, where they seem to have been hesitant to cross large bodies of water to migrate. The first stork to migrate appeared to have followed main roads and motorways and managed to cross the channel to Calais, then travelled further south into Europe. It is thought that near Luxembourg it probably met with other storks and changed direction making its way across France and Spain, then over to Morocco where it stopped near Rabat at a known landfill site.

Although the project is still at its early stages, UEA researchers and conservationists can already see the benefits of their tracking; for instance they’ve been able to see that a few storks from the project have migrated, whilst others have stayed in Britain. This research will aid conservationists in understanding how to make improvements to the reintroduction programme, in understanding how to better release them next year and how flocks are aggregated.

The tracking devices that UEA Researchers developed with Movetech Telemetry are a fantastic tool to allow other researchers to obtain in-depth movement data about animals. They are aiming to be involved in advising how best to reintroduce these species to Britain but also in understanding the different movement strategies of animals that are released. The trackers are also now available to purchase for commercial use and can be particularly helpful to those in the agriculture industry.