The Balkan Peninsula is considered one of the richest regions in Europe in terms of biodiversity of land vertebrates. Bulgaria alone is home to more than 400 species of birds. In the past, the saker falcon used to be one of its most common bird species as hundreds, perhaps thousands of pairs used to breed in the country.
Due to a number of anthropogenic factors however, by the end of last century their breeding population was effectively destroyed. Targeted monitorings were conducted throughout the former occupied territories in the beginning of the 21st century, but no birds were found.
For a while, the only breeding sakers in Bulgaria could be found in captivity. As part of the initiated by nature conservation NGOs reintroduction programme, birds from various breeding centres in Europe were obtained in order for a breeding group to be formed in the Wildlife Rehabilitation and Breeding Centre (WRBC) - Green Balkans, in Stara Zagora, Bulgaria.
The WRBC is a specialised unit of Green Balkans - Stara Zagora NGO, concerned with the rehabilitation, treatment, recovery and release of protected wild animals and animals threatened with extinction.
It is the only facility of its kind in Bulgaria.
The saker falcon breeding aviaries have special adaptations specific to the species. They are constructed from solid wood panels, which restrict visual contact with humans. Each cage has mesh roofing, which allows natural light and fresh air flow.
Their offspring are the only hope for restoring the saker falcon population in Bulgaria. Reared solely by their parents, the juveniles' first and last direct contact with people is for the veterinary check-up right before being released in the wild.
Approximately at-30-days old, the saker chicks are evaluated for hacking through the surveillance cameras.
Footage: Green Balkans - Stara Zagora NGO
The young falcons are marked for identification purposes with a set of two rings and a microchip. The metal ring indicates year and place of hatching. The colour of the PVC ring changes annually in order to facilitate the easier identification of observed birds in the wild, and it includes a number-letter combination.
During the examination the falcons are treated against ecto- and endoparasites.
Taking morphological measurements like weight and tarsus bone girth is done in order to determine the birds’ sex prior to releasing them. Females always weigh more than males - they are around one kilo, while male sakers weigh 800 gr on average.
In preparation for the releases, the solar panels powering the surveillance cameras in the field are cleared from leaves and branches which could be in the way.
After the vet check, the sakers are placed in adaptation aviaries - hacks, imitating a nest and installed at around 10m of height on oak trees. The falcons spend ten days closed inside, in order to change all their feathers, and get accustomed to the food provision and the area through the mesh top, preventing attacks from predators in a period when the young birds are still vulnerable.
The area chosen for the reintroduction of the saker falcons was evaluated beforehand for the availability of food sources, such as pigeons, grassland birds and ground squirrel colonies.
The sakers’ feeding tables are three-metre-high platforms, visible from the hacks. Food is placed daily for the young falcons in order to keep them in the area longer, while they learn to hunt by themselves.
Small mammals like the ground squirrel are easily scared and often hide in their tunnels upon the approach of people. In order to record them from so close, first the area was scouted for suitable holes and then a tripod with a camera was placed close to one. The recording was done remotely through a Wi-Fi connection, after the animals sensed there were no people around and came out. Ground squirrels are a preferred prey for saker falcons. In Europe the birds' population is dependent on that of the souslik.
On the tenth day after hacking, the lid of the hack is opened and the sakers can fledge when they feel ready to do so - often on the same, or in the following days.
While the sakers are in the hack area - for up to four months, the team supplies them with food twice a day - morning and evening. The feeding mechanism at the hack is a simple pulley mechanism with a bowl to reduce bird/human interactions. Ideally, the birds form no connections of humans with food.
The sakers' survival and consecutive return to breed in the region of release rely on them spending their post-fledging dependence period (40 days approx.) in the area. The species perform the so-called natal homing - most of the adults will return to breed near the place they were reared. Keeping them there is dependent on food provision, and monitoring each individual -- differing only by ring numbers -- is crucial for conclusions on the success of the released groups of birds.
It is often the case that the ring number is not seen as soon as a saker falcon is observed. They can stay with their backs turned to the camera, or with the other leg in front, or it can be hidden from wings or feathers. In that case the only thing that can be done is to be patient and wait for the bird to change position.
From initially spending more time on the ground and close to the aviaries in the days after fledging, the saker falcons gradually learn to fly better and further away, before they disperse around the end of July-beginning of August.
In 2022, a third saker falcon pair was discovered in Bulgaria following the 20 years without confirmed breeding of the species in the country (1998-2018).
All of the birds forming these recently discovered wild pairs are marked with the set of colour and metal rings, confirming who they are, and that they were released as part of the programme.
In spite of conservationists having installed nesting platforms on trees, all the wild nesting sakers chose to breed on electricity pylons instead. Installing the platforms showed us the scarcity of old-growth lone-standing trees left in suitable areas, as most had been removed either for timber or to clear land for crop fields. Nevertheless, the birds proved that given the chance they can adapt even to fully man-made structures.
The long power lines crossing the country are now being monitored for saker nests.
Footage: Ivaylo Klisurov
The story represents conservation work part of project Saker Falcon Reintroduction in Bulgaria, funded by the Mohamed Bin Zayed Raptor Conservation Fund (United Arab Emirates) and Armeec JSC (Bulgaria). The fieldwork was carried out thanks to the team of the Wildlife Rehabilitation and Breeding Centre - Green Balkans, the Bulgarian and international volunteers, and the mayor and people of Malko Kadievo village.
No animals were harmed during the process. The material was taken between 2020-22 during personally performing the conservation work.