At the end of August, the team of the Life for the Lesser Kestrel project (LIFE19 NAT/BG/001017), implemented by Green Balkans under the European Union’s LIFE Programme, conducted its annual coordinated count of Lesser Kestrels (Falco naumanni) at their pre-migration aggregations.
All currently known aggregation sites in Bulgaria were surveyed simultaneously. The monitoring also involved volunteers from the “BARBATUS” Student Environmental Club at Trakia University – Stara Zagora, as well as representatives of the Bulgarian Biodiversity Foundation (BBF), the “Sakar Nature Park” Association, Alexandra Popova, Lyubomir Profirov and Ivaylo Borisov.
More than 450 Lesser Kestrels
During the monitoring, sites in different parts of the country were surveyed, including the Sakar, Sredna Gora and Stara Planina mountain ranges, the Besaparian Hills, the Upper Thracian Plain and other areas where the species traditionally gathers before the onset of autumn migration.
This year’s results are encouraging. More than 450 Lesser Kestrels were recorded, compared with around 270 birds last year. This represents an increase of as much as 67% compared with the previous year!
Alongside the Lesser Kestrels, Common Kestrels (Falco tinnunculus) were also observed at some of the roosting sites. The two species have similar ecology and often use the same roosting sites in the period before the onset of autumn migration. But our experienced observers do not overlook even the smallest details and carefully record not only Lesser Kestrels, but also the other species sharing these roosting sites.
Marked Birds Tell the Story of the Colonies
Birds carrying ornithological rings are of particular interest to researchers. These markings make it possible to trace individual birds’ origins and establish their links to already known breeding colonies.
Even more intriguing is the fact that, alongside marked birds, numerous unmarked Lesser Kestrels are also being observed. This raises important questions about the origin of the birds gathering in Bulgaria before migration.
Some of these birds may originate from breeding sites in Bulgaria that have not yet been discovered. Nor can the possibility be ruled out that some birds arrive from neighbouring countries, including Greece, Türkiye and the Republic of North Macedonia. This highlights the importance of monitoring the species beyond its known breeding colonies and covering all suitable habitats used by Lesser Kestrels during migration.
Modern technology is also playing an increasingly important role in tracking the birds. Thanks to satellite-tracking devices provided by Global Messenger, specialists can follow the movements of marked birds, track their migration routes, and more easily locate sites where they gather before migration. Combining remote tracking technologies with direct field observations makes it possible to identify and study sites that might otherwise remain difficult to detect.
What Do Lesser Kestrels Eat During Migration?
The monitoring also includes the collection of pellets – compact remains of undigested food that birds regurgitate. These may contain bones, fur, feathers and the chitinous remains of insects. By analysing these pellets, the team will have the opportunity to investigate what Lesser Kestrels feed on during this important period. Before embarking on their long migratory journey, the birds need to build up sufficient energy reserves, making access to nutritious, energy-rich food essential.
Of particular interest is the fact that no dedicated study of the Lesser Kestrel’s diet during migration has been conducted to date. We will therefore investigate what exactly makes up their diet during the pre-migration aggregations and to what extent the available food provides them with the resources they need for the exhausting journey to their wintering grounds, covering more than 4,000 km in one direction alone.
From Successful Recovery to the Bigger Picture
Thanks to the efforts of Green Balkans through the Life for the Lesser Kestrel project, Bulgaria is now home to three separate and independent colonies of the species, located mainly within protected areas of the European Natura 2000 network.
The development of these colonies contributes to an increase in the national population and an expansion of the species’ geographical range in Bulgaria. At the same time, this creates additional challenges for monitoring and conserving the species.
This is why monitoring pre-migration aggregations is becoming increasingly important. The methodology for studying these aggregations was developed by the Life for the Lesser Kestrel project team and is now being successfully applied for another consecutive year.
Every bird counted, every marked Lesser Kestrel and every pellet collected adds another piece to the puzzle of migration, helping us better understand where these remarkable little falcons live, where they come from and what they need.
We would like to thank all the volunteers, partners and nature enthusiasts who took part in the count and helped make this important study for science and nature conservation possible!
All currently known aggregation sites in Bulgaria were surveyed simultaneously. The monitoring also involved volunteers from the “BARBATUS” Student Environmental Club at Trakia University – Stara Zagora, as well as representatives of the Bulgarian Biodiversity Foundation (BBF), the “Sakar Nature Park” Association, Alexandra Popova, Lyubomir Profirov and Ivaylo Borisov.
More than 450 Lesser Kestrels
During the monitoring, sites in different parts of the country were surveyed, including the Sakar, Sredna Gora and Stara Planina mountain ranges, the Besaparian Hills, the Upper Thracian Plain and other areas where the species traditionally gathers before the onset of autumn migration.
This year’s results are encouraging. More than 450 Lesser Kestrels were recorded, compared with around 270 birds last year. This represents an increase of as much as 67% compared with the previous year!
Alongside the Lesser Kestrels, Common Kestrels (Falco tinnunculus) were also observed at some of the roosting sites. The two species have similar ecology and often use the same roosting sites in the period before the onset of autumn migration. But our experienced observers do not overlook even the smallest details and carefully record not only Lesser Kestrels, but also the other species sharing these roosting sites.
Marked Birds Tell the Story of the Colonies
Birds carrying ornithological rings are of particular interest to researchers. These markings make it possible to trace individual birds’ origins and establish their links to already known breeding colonies.
Even more intriguing is the fact that, alongside marked birds, numerous unmarked Lesser Kestrels are also being observed. This raises important questions about the origin of the birds gathering in Bulgaria before migration.
Some of these birds may originate from breeding sites in Bulgaria that have not yet been discovered. Nor can the possibility be ruled out that some birds arrive from neighbouring countries, including Greece, Türkiye and the Republic of North Macedonia. This highlights the importance of monitoring the species beyond its known breeding colonies and covering all suitable habitats used by Lesser Kestrels during migration.
Modern technology is also playing an increasingly important role in tracking the birds. Thanks to satellite-tracking devices provided by Global Messenger, specialists can follow the movements of marked birds, track their migration routes, and more easily locate sites where they gather before migration. Combining remote tracking technologies with direct field observations makes it possible to identify and study sites that might otherwise remain difficult to detect.
What Do Lesser Kestrels Eat During Migration?
The monitoring also includes the collection of pellets – compact remains of undigested food that birds regurgitate. These may contain bones, fur, feathers and the chitinous remains of insects. By analysing these pellets, the team will have the opportunity to investigate what Lesser Kestrels feed on during this important period. Before embarking on their long migratory journey, the birds need to build up sufficient energy reserves, making access to nutritious, energy-rich food essential.
Of particular interest is the fact that no dedicated study of the Lesser Kestrel’s diet during migration has been conducted to date. We will therefore investigate what exactly makes up their diet during the pre-migration aggregations and to what extent the available food provides them with the resources they need for the exhausting journey to their wintering grounds, covering more than 4,000 km in one direction alone.
From Successful Recovery to the Bigger Picture
Thanks to the efforts of Green Balkans through the Life for the Lesser Kestrel project, Bulgaria is now home to three separate and independent colonies of the species, located mainly within protected areas of the European Natura 2000 network.
The development of these colonies contributes to an increase in the national population and an expansion of the species’ geographical range in Bulgaria. At the same time, this creates additional challenges for monitoring and conserving the species.
This is why monitoring pre-migration aggregations is becoming increasingly important. The methodology for studying these aggregations was developed by the Life for the Lesser Kestrel project team and is now being successfully applied for another consecutive year.
Every bird counted, every marked Lesser Kestrel and every pellet collected adds another piece to the puzzle of migration, helping us better understand where these remarkable little falcons live, where they come from and what they need.
We would like to thank all the volunteers, partners and nature enthusiasts who took part in the count and helped make this important study for science and nature conservation possible!
