In the summer of 2019, we set out to implement another rewilding project - GPS tagging griffon vultures in the Côa Valley in northern Portugal. Since July 2019 we have been supporting this vulture conservation intervention in collaboration with our partners, Rewilding Portugal, at the location of our Wildfire Restoration project. The detailed behavioural data acquired through this project is already providing answers to questions that before were only a matter of speculation. 

On the ground report: GPS Tagging Griffon Vultures

The first 5 griffon vultures are tagged with GPS devices. Matt, our co-founder, heads to the field to assist with the tagging and vulture conservation project. 

Data analysis reveals where the vultures are foraging and what they are feeding on. 

Tiago, our conservation biologist, heads back to the Côa Valley to assist in the tagging of one more griffon vulture. 

Learn more about why we are tagging Griffon vultures and vulture conservation.

The scarcity of wild herbivores in western Iberia means that griffon vultures (Gyps fulvus) tend to feed on the abandoned carcasses of domesticated animals such as cattle and sheep. This makes them particularly vulnerable to changes in livestock farming practices. In 2001, following the bovine spongiform encephalopathy crisis (“mad cow disease”), the European union prohibited the abandonment of livestock carcasses in the field to prevent spread of the disease. The reduced food availability contributed to the decline of vulture populations in the area. 

Since then, however, the Iberian population has shown an impressive comeback. In the Côa valley, there were less than 10 breeding pairs during the 1990s and this number rose to 74 by 2015. The comeback to the areas was facilitated by the protection of suitable nesting habitat within the Faia Brava reserve. However, the key driver for the resurgence of griffon vultures throughout the Iberian Peninsula appears to have been a relaxation of the EU policy which once again allowed farmers to leave livestock carcasses in the field. 

Spain reverted it’s legislation before Portugal did. This explains a previous finding that vultures tagged in Spain clearly avoid Portuguese territory. In Portugal, abandoning livestock carcasses in the field became legal again in 2017 but obtaining the required permissions is a highly bureaucratic process which means that few farmers have changed their practices. 

Although the griffon vulture population in the Coa Valley has been monitored in the past, we could only guess where the vultures were foraging and what they were feeding on. This is where our vulture conservation project comes in by sponsoring the GPS devices required to track the movement patterns of griffon vultures.

These solar powered devices transmit precise geographical information without the need to recapture the individuals and have built in accelerometers which provide additional information about the way in which the vulture is moving at a given moment in time. This data can be used to determine when the vulture is resting, flying or foraging.

Moreover, this data can be used to identify the time and location of likely feeding events. By going to the field and looking for signs of feeding (such as carcass remains and vulture feathers), these feeding events can be confirmed and we can obtain information about what the vultures were feeding on, which in turn aids future vulture conservation efforts.

Contributing to the area's ambitious rewilding goals

This work of GPS tagging griffon vultures is part of a larger project that is currently being implemented in the region. The project "Scaling Up Rewilding in the Greater Côa Valley" is being led by Rewilding Europe and focuses on reinforcing a 120,000-hectare wildlife corridor that will improve connectivity in the landscape between the Malcata mountain range and the Douro Valley. This project is financed by the Endangered Landscapes Programme, which is managed by the Cambridge Conservation Initiative and funded by Arcadia, a charitable fund of Peter Baldwin and Lisbet Rausing.

Carlos Pacheco, raptor expert at ATNatureza.

GPS tagging the vultures will allow us to see whether the birds are feeding mostly on the carcasses of domestic livestock, or also on wild herbivores, and how often they visit vulture feeding stations, which will ultimately enable us to improve the management of food sources for the birds and support the restoration of trophic chains.

This interactive map was created with the data from 4 of the Griffon vultures tagged in the summer of 2019. You can follow the journey of each individual and see the distance travelled up to that point (by clicking on the bird's icon).

GPS tagging vultures gave us invaluable insight to the birds’ foraging behaviour. The data will support the restoration of food chains & future vulture conservation.

GPS Tagging Griffon Vultures

The griffon vultures that we GPS-tagged in the summer of 2019 have generated huge amounts of data which had to be processed to reveal the most interesting insights and patterns. Here is a summary of the main findings that emerged from data about the behaviour of 4 of the tagged birds.  The analysis was performed by our partners Sara Aliácar, André Couto, Carlos Pacheco, João Neves and João Paulo Silva.

Almofala, one of the griffon vultures we tagged in the summer of 2019 was found dead after the tracking data suggested it had not moved for several days. Although this is unfortunate, events like this can lead to important insights into the causes of mortality in the population. In this case, the bird appears to have died of natural causes because the necropsy showed no evidence of shooting or poisoning.

The remaining vultures (Algodres, Brava, and Jardo) stayed active until the GPS signal was lost allowing a large amount of valuable information to be collected.

Birds were tracked for an average period of 148 days and the combined position and accelerometer data have allowed 160 potential feeding events to be identified. This has given us the first insight into their foraging behaviour. 

The great majority of feeding events took place in Spain. Interestingly, abandoned carcasses in extensive farming areas appear to be providing most  of the food for these griffon vultures. However, there was also evidence of feeding in natural areas and intensive or semi-intensive farming areas. Only a small percentage of the feeding events took place at vulture feeding stations, which are maintained to provide supplemental feeding for endangered scavengers such as the Egyptian vulture.

Findings from initial data analysis from GPS tagging vultures

May 2020 Project Update

Findings from initial analysis of GPS tracker data

Vulture Update - May 2020

Mortality

Feeding

Interactive map