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Five Griffon Vultures tagged in Western Iberia to reveal feeding behaviour

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Griffon Vulture feeding (c) Bruno Berthemy

Five Griffon Vultures are now equipped with transmitters and accelerometers in the Western Iberia in northern Portugal. The data collected from these vultures will shed new light on their foraging behaviour in the region and help inform actions to restore the natural food chain in the area.

Invaluable data

Associação Transumância e Natureza (ATN) and Rewilding Portugal tagged the vultures in July as part of the five-year “Scaling Up Rewilding in Western Iberia” project. The data collected will help support the restoration of natural food chains in the area and subsequently, the comeback of the species. Apart from fitting the birds with transmitters, they equipped them with an accelerometer – the first time the species are monitored this way in the region. This technology will show when they are resting, flying or foraging, and will provide invaluable insight into where the vultures go to feed and what types of carrion they feed on. 

“The tagging will allow us to see whether the vultures are feeding mostly on the carcasses of domestic livestock, or also on wild herbivores, and how often they visit vulture feeding stations,” says Carlos Pacheco, a project manager at ATN. “This will ultimately enable us to improve the management of food sources for the birds and support the restoration of trophic chains.”

Food chain restoration

The restoration of trophic chains is an essential element of rewilding the valley. Currently, both Griffon Vultures and Egyptian Vultures rely on a local network of artificial feeding stations provided by organisations such as ATNatureza. The project aims to increase the availability of natural carrion in the area. They do so by encouraging Portuguese authorities to allow local farmers to leave domesticated herbivore carcasses in the field, and by boosting the local population of wild herbivores, such as roe deer.

Comeback of Griffon Vultures in the region

Griffon Vulture in flight (C) Rewilding Europe Bogdan Boev

According to the monitoring data since the 1990s in and around the Greater Côa Valley, Griffon Vultures have made a dramatic return to the Western Iberia rewilding area. There are estimated to be around 200 breeding pairs in the project area, which includes the SPA Vale do Côa, Serra da Malcata Nature Reserve and Douro International Nature Park. Their comeback would be further facilitated if authorised Portuguese farmers left their livestock carcasses in the field.

Regulatory impact and working for change

In 2001, after the “mad cow disease” crisis, the European Union prohibited the abandonment of livestock carcasses. This, in turn, had a significant impact on vulture populations, which relied on these carcasses in the absence of wild herbivores.

The EU legislation has now relaxed and allows livestock carcasses to be once again left in nature (under special conditions). But not all European countries have chosen to implement this change. Until very recently, this meant that farmers were allowed to leave carcasses in large swathes of the Spanish countryside, yet their Portuguese counterparts were compelled to remove them. We reported the disparity last year when recent research showed GPS-tracked griffon and cinereous vultures on the Iberian peninsula almost exclusively avoiding Portuguese territory.

Recent changes to Portuguese regulations allow certain livestock carcasses, exclusively from farming, to be left outside of artificial feeding stations in areas that the Institute of Nature and Forest Conservation (ICNF) considers important for vulture conservation.

“Going forward, the Rewilding Portugal team and partners will work with national authorities to further develop an extensive network of farmers in the Côa Valley and Douro International Nature Park who are authorised to leave carcasses in the field,” explains Sara Aliácar, a conservation officer of the Rewilding Portugal team who took part in the tagging.

Restoring natural food chains in the Western Iberia

The vulture tagging was carried out as part of the five-year “Scaling Up Rewilding in Western Iberia” project. Kicking off in 2019, and funded by a generous grant from the Endangered Landscapes Programme, this will see Rewilding Europe (through Rewilding Portugal) and local partners further develop a 120,000-hectare wildlife corridor in the Greater Côa Valley.

Sponsored by Mossy Earth, the tagging was carried out by Associação Transumância e Natureza (ATNatureza), together with members of the Rewilding Portugal team. As scientific collaborators, CIBIO-InBIO and Movetech provided the transmitters and will also support with data analysis and the dissemination of results.

Another group of griffon vultures will be tagged towards the end of the “Scaling Up Rewilding in Western Iberia” project. This should highlight what impact changes in the availability of food have had on the birds’ behaviour and distribution.

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