How do we boost Bearded Vulture breeding success in captivity to support conservation projects?

Marie Antoinette lays her third egg (c) VCF
Marie Antoinette lays her third egg (c) VCF

When the snow is melting, the rain is more frequent and the food supply becomes more plentiful in spring, that's the ideal period to start breeding for most birds. But, that's not the case for the Bearded Vulture, Europe's rarest vulture species. Bearded Vulture breeding pairs begin exhibiting breeding behaviour as early as October in the wild. This special breeding period is related to the chicks' diet, which cannot digest bone, so the species has evolved to hatch towards the end of winter when there is potentially a plentiful supply of carrion. For example, animals that died from avalanches and are then exposed in the thawing snow or animals that die towards the end of the season from not surviving harsh conditions, leaving plenty of animal carcasses for the parents to feed their chicks. 

 

As the Vulture Conservation Foundation (VCF) has been working for the conservation of the species for over 30 years now, successfully reintroducing it to the Alps alongside partners by releasing captive-bred birds into the wild, we have become experts when it comes to the Bearded Vulture. Currently, we coordinate the Bearded Vulture Captive Breeding Network (Bearded Vulture EEP). Alongside our many partners over the years, we have developed processes and protocols to boost the species' breeding success in captivity to expand our conservation initiatives. 

 

Working to produce as many chicks as possible

Second eggs of  M. Antoinette (female) and Joseph (male) this breeding season (c) VCF
Second eggs of M. Antoinette (female) and Joseph (male) this breeding season (c) VCF

When breeding pairs are established, which is a challenging task and is a whole other story, they start exhibiting breeding behaviour every year as early as September in captivity. They begin engaging in mutual preening, showing aggression towards neighbouring pairs and playing with nesting materials such as sticks and wool. At this period, human keepers are alert as it is crucial to provide the necessary material at the right time for pairs to build a high-quality nest to avoid egg damageNest building for Bearded Vultures usually begins around three months before egg-laying, with copulations occurring anywhere between 50 and 90 days. This breeding season, the pair in Armenia laid their first egg very early, on Friday, 29 November 2020. Following the egg-laying, pairs incubate their clutch for around 52 days. At this time, there are ways to increase the number of eggs produced. 

 

In some centres like the VCF-managed Specialised Bearded Vulture Breeding Unit at the Recovery Centre Vallcalent, owned by Generalitat de Catalunya, we use some methods to increase the number of eggs laid and improve the likelihood of hatching. This Centre hosts the most challenging pairs within the Bearded Vulture EEP that had little or zero breeding success before arriving at Vallcalent. In this Centre, some eggs are removed from the nest to encourage the pair to lay more eggs and increase the chances that some of them are fertile. Furthermore, the eggs are removed because most Bearded Vultures at the Centre cannot properly incubate their clutches due to physical conditions or behaviour problems, for example, M. Antoinette has a bad leg and can't make a bowl, and Dama, the female that recently died, used to bury the eggs in wool. So, the eggs removed are then artificially incubated, a method developed by the VCF. This method includes thermal shock where eggs are exposed to outside temperatures four times per day for five minutes, promoting the gas exchange (CO2 and O2) and, consequently, the embryo's development while also manually turning the egg 180 degrees. It replicates the behaviour of Bearded Vulture pairs since when one parent leaves the incubation post, the egg receives a thermal shock until the other parent starts incubating. It is important to mention that dummy eggs are also placed in nests if eggs are removed so that the pair can then adopt and rear the chicks once they hatch.

Bearded Vultures are not the simplest birds. When chicks arrive, some pairs do not accept them, which can lead to chicks' death. Furthermore, a pair cannot rear two chicks due to an evolutionary behaviour called 'cainism' where the older chick kills the younger one. So, this means that some facilities where chicks hatch cannot naturally rear newly hatched chicks, which can lead to human imprinting. Therefore, chicks are transferred to other centres to be adopted. Some centres like the Bearded Vulture Captive Breeding Centre of Guadalentín, which is managed by the VCF following an agreement with the Junta de Andalucía, specialise in double and triple adoptions, enabling them to host and rear many chicks every year. The possibility of adoption by Bearded Vultures enables chicks to develop their natural instincts, and so be able to be released to the wild and breed with their conspecifics when they reach sexual maturity. However, in 2020, due to the COVID-19 pandemic and the travel restrictions, it was not possible to carry out all the necessary transfers between facilities. So, the Vulture Conservation Foundation (VCF) developed emergency plans and protocols, where facilities could adopt specific measures to rear chicks in a way to avoid human imprinting.  

 

All these efforts are crucial to produce enough chicks to provide to reintroduction or restocking projects, and help restore Bearded Vulture populations in Europe!

 

Number of eggs laid up until 22 January 2021

The Bearded Vulture breeding season is in full swing, and so far pairs laid many eggs! Currently, the Bearded Vultue EEP welcomed 45 eggs in total — 15 eggs in Spain, 4 in France, 2 in Italy, 9 in Austria, 1 in Switzerland, 3 in Germany, 7 in the Czech Republic, 1 in Russia, 1 in Bulgaria and 2 in Armenia! Everything looks promising so far, and we hope for a productive breeding season ahead, with many chicks hatching! 

 

Captive-breeding Bearded Vultures

The Vulture Conservation Foundation (VCF) coordinates the Bearded Vulture Captive Breeding Network of zoos, specialised breeding centres, recovery centres and private collections on behalf of EAZA. This involves closely working with over 40 partners of zoos and specialised centres across Europe to ensure the best breeding results from the 180 birds within the Network. Thanks to these captive breeding efforts, since 1978, a total of 585 Bearded Vultures chicks have been produced in captivity, out of which, 343 have been released into the wild to reintroduce or restock the species population across Europe!

 

To follow the news of the breeding season, follow #BeardedVultureBreedingSeason on Facebook and Twitter.

 

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