David Izquierdo, our Bearded vulture captive breeding assistant, has been in the field, monitoring the recently released Bearded vultures in Maestrazgo for 45 days. In the interview that follows, he shares his insights, experience and the updates of the birds that have now fledged.
Can you talk us through the recent reintroduction of the two Bearded vultures in Maestrazgo?
Photographs from the release (c) VCF
This year, we released two captive-bred Bearded vultures in the PN de la Tinença de Benifassà as part of the Bearded vulture reintroduction project at the Sierra del Maestrazgo. The oldest one of them, BG1033 “Bassi”, was the 2nd of the four eggs that the pair BG371 “Tejo” and BG103 “Dama” laid at the specialized breeding centre (SBC) of Vallcalent this season. The egg was artificially incubated throughout the entire period until it hatched by itself on the 1st of March. The chick was hand-reared for the first eight days of his life, by Álex (Bearded vulture captive breeding manager) and myself, as Bearded vultures can be safely handled without risking imprinting for around 10-12 days. On the 9th of March, he was taken to the SBC Guadalentín to be adopted by a foster pair, since we didn’t have more adults available to do so. On that very same day, the 9th of March, BG1040 “Boira” hatched late in the evening at the SBC Guadalentin; Boira is the 1st egg of a double clutch laid by the productive pair BG337 “Borosa” and BG317 “Toba”. Her egg was also incubated artificially and hand-reared before being given for adoption. Both birds were transported to the release site at the Maestrazgo on the 5th of June and taken to the hacking cave on the 6th. They were, respectively, 97 and 89 days old.
Why is it important to monitor the birds after their release into the wild?
Monitoring of released individuals in any reintroduction project is not only important but essential.
We release Bearded vultures using the hacking method, which is more or less the “natural” way of fledging. The role of the parents at that time is to protect nestlings against predators, supply them with food and provide social contact.
When releasing 90 days old nestlings, they are large and strong enough to defend themselves against any natural predator (birds of prey or foxes). They are also able to eat and prepare food alone, but not to search for it. We should have in mind that their learning and adaption capacity are also in their maximum phase. Further, to encourage social contact, we always introduce a minimum of two nestlings at each hacking site. Nevertheless, Bearded vulture nestlings have the peculiar aggressive behaviour called “cainism”, which is present during the whole nestling period, leading to heavy fights between nestlings.
During this period, the human keeper has to substitute a big part of the parent functions, mainly the food supply. Furthermore, if fights take place, the keeper has to intervene. If not, severe injuries can occur.
Also, during the first weeks as fledglings, the so-called Post-Fledging Dependence Period (PFDP), they are still dependent on their parents to protect them against other birds of prey when flying in search of food. The human keeper plays the parental role again by offering food until they become independent. During the first three flying weeks, injuries can occur because of flight fights with other birds of prey. That’s why the presence of trained staff is essential to recognize if a fledgling has been seriously injured or not. This is the flight learning period. After this period, they can evade attacks from other birds. During this period, staff continues monitoring the birds, to assure that daily food is available in the hacking area, and the birds are developing well.
What is it like monitoring the vultures?
(c) VCF and Dominic Houghton
Working in the fields is quite demanding both mentally and physically, even though it might not be evident by a third party. The fieldwork consist of monitoring the daily activities of the young birds while they are still in the hacking site and during the first weeks after fledging since they are still dependent on our feeding. We also keep track of their behaviours and collect data that can give us information on the daily condition of the birds and can be used in models and analysis in order improve our knowledge of the species to adapt the methodology in the future.
A typical day consists of waking up at around 4:30 am, preparing food for the birds, and driving to Rosell for 30 minutes, where the morning shift team meets. From there we take the off-road car and drive from Rosell to Bel, and then take the unpaved road to reach the hacking site. From the area where we leave the cars, we still need to walk for about 20 minutes to the site. Once we arrive, we start the work by providing the birds with food and water, and begin the monitoring, which consists of entering data of each bird on a daily table, directly into the computer. The monitoring is done at the observation hut or outside, following the birds once they have fledged. By 13:30, the team covering the afternoon shift arrives, overlapping with the morning team to exchange information on the situation and get a summary of the events of the morning. The afternoon shift lasts until 21:00, when the birds are already ready to roost for the night and are not active anymore.
When and how did the birds fledge?
Bassi was the oldest bird of the two young vultures, and thus it was expected for him to leave the hacking cave earlier than his “companion” Boira. Usually, females are the dominant birds during hacking periods, so Boira established her dominance from the very beginning, as expected. As a result, she was often aggressive towards Bassi. In one of these episodes of hostility, Boira forced Bassi out of the enclosure at a very early age, only 112 days old (Bearded vultures fledge at 117 days on average). For the following two days, Bassi remained near the hacking site and didn’t attempt flying, but eventually managed to fledge on the 24th, at 114 days of age. For the next four days, he didn’t come back to eat, so we started to worry and attempted several actions. But eventually, he decided to come back by himself and started eating in one of the feeding sites we had set up. Since then, he’s been visiting the area regularly, but has finally reached that stage when young birds emancipate and has discovered further feeding sites, so his visits to the hacking area are becoming more and more infrequent.
Boira, unlike her companion, has taken an unusually long time to fledge, and only did so on the 23rd of July at the mature age of 136 days old. Although there are other cases of such “late bloomers” in the history of releases since we’ve been monitoring the releases, it’s highly unusual. However, despite her long time in the hacking, she’s managed to find food just three days after fledging, which gives us hope for the future.
Special thanks are due to everyone who helped in reintroducing and monitoring the Bearded vultures in Maestrazgo! The staff of VAERSA and Generalitat Valenciana were in the field for days together with David, monitoring the vultures. Furthermore, we also want to thank Red Eléctrica de España for funding the observation hut and parts of the equipment used.
Connecting populations of Bearded Vultures in Spain
The Maestrazgo region of Spain was historically a breeding site for Bearded Vultures and while there are no resident population the area is regularly visited by individuals released in Andalusia. The project to reintroduce the species to the region began in 2018 with the aim of establishing a wild breeding population that will bridge the populations in the Pyrenees and Andalusia, similar to the LIFE GYPCONNECT project in France that connects populations in the Pyrenees and the Alps. Over the course of the project captive-bred birds wil be released in specially constructed hacking sites in the Parque Natural de la Tinença de Benifassà and in a unique experiment the team, in close consultation and collaboration with us here at the Vulture Conservation Foundation, will translocate adult non-breeding or floater birds from the population in the Pyrenees to the Maestrazgo region to test how effective this method is and if that has an effect on the reproductive productivity of the Pyrenean population. As part of the project the released birds will be monitored by fitting them with GPS transmitters to better understand how the move around the region and to encourage movements of birds to the region a series of supplemetary feeding stations will be created.
The project is led by the Generalitat of Valencia, in collaboration with the Autonomous Communities from Aragón and Catalonia, the Spanish Ministry of Agriculture, Fish, Food and Environment and the us here at the Vulture Conservation Foundation.