This summer, UEA PhD student Jethro Gauld joined other researchers in the Alentejo region of Portugal to assist Marta Serra Acacio with monitoring white stork Ciconia ciconia colonies and fitting GPS tags to juvenile birds before they fly the nest. In part this was to learn about the methods used to monitor this species as part of a long term monitoring project co-ordinated by Dr Aldina Franco and Dr Inês Catry which has been running since 2012. This season, Marta, Inês and research assistant Bruno managed to also tag 50 adult storks.
Storks are a good study species for studying with satellite telemetry because they are relatively common, they are a large bird which can comfortably carry a tag weighing 50g for extended periods. The juveniles are relatively easy to tag in the nest (the adults are a bit more difficult) and they are a species a lot of the general public are familiar with. They also have an interesting migration strategy, historically European white storks have migrated to Africa. However, an increasing number of storks (particularly within Iberia) are becoming resident or are shortening their migration due in part to the year round supply of food at rubbish dumps. The satellite tags (along with the other on board sensors like the accelerometer, thermometer, gyroscope and barometer) allow us to relate the behaviour of the storks to other factors such as land use, the weather and the behaviour of conspecifics. Work is ongoing to understand how human driven changes to the landscape such as climate change, agricultural intensification and the planned closure of rubbish dumps will continue to alter the migration strategy of these birds and their breeding success.
The wireless feature of the GoPro provided by the EnvEast DTP was used in combination with a camera pole to monitor nests and take photographs with minimal disturbance to chicks.
This long term project has allowed the white stork team (in collaboration with other institutions such as Movetech, British Trust for Ornithology, University of Lisbon and the University of Herriot Watt) to develop the technology further. This has allowed additional sensors (mentioned above) to be incorporated into the devices along with the GPS and for the accuracy and frequency with which data can be recorded and transmitted through the mobile telephone network. Smaller Movetech tags have been developed (in the region of 22g) and currently there is work to miniaturise the devices further. When we fit the tags, we also ring the birds with colour rings and metal rings so people in the field can relate the movements of the bird observed in the telemetry data to birds they see while out on survey. This helps us understand the signals from the on board sensors and how they relate to the behaviour and movements of the birds. It is also a useful back up for cases where the tag falls off or stops working.
A large stork colony with nests constructed on high voltage power line pylons (Photo Credit: Marie-Morgane Rouyer)
As well as behavioural ecology, the data from the tags can help us understand the other challenges facing these birds. Humans and storks have lived together for millennia with storks often benefitting from human structures as safe places to nest. However in recent years, they have increasingly started to use electricity pylons and poles to nest. This brings them into regular risk of electrocution and collision on power lines which can also result in costs to humans in the form of fires and damage to infrastructure. This is why there is now a growing interest in using this data to identify regions where are interacting frequently with energy infrastructure so we can better target mitigation such as line marking and insulation of electrical components on power lines.
This is important as the energy grid is expected to expand massively in the next few years to support the transition to renewable energy. There is also growing interest in live detection of impacts; this has two main applications: 1. Detection of mortality of the bird due to collision and 2. Detection of the bird being shot. Unfortunately hunting is an ongoing problem for migratory birds; thousands if not millions of birds are shot every year. Being able to recognise the characteristics of the accelerometer data associated with either a collision or shooting event will help us remove the ambiguity surrounding why the bird disappeared or stopped moving in a particular location.
Recovered tag with neatly cut straps suggesting that the bird had been illegally killed before the tag was removed.
While in Portugal we detected that a young tagged stork had stopped moving but when we went to investigate, we discovered that the bird had probably been illegally killed. There was no carcass and only the tag with two neatly cut straps remained. The exact time and how the bird was killed remains a mystery so there is not any feasible way of bringing the case to the police; this same frustration is felt by those working in the UK to protect our birds of prey where raptors often disappear on shooting estates.
The stork tagging season may be nearly over for another year but fingers crossed we see our tagged birds avoid the hunters and power lines so they return next year when the white stork team will be out in Portugal again to continue this long term monitoring project.
Storks and black kites congregate in large numbers at landfills and rubbish dumps.