Valentijn S. van Bergen
@vsvanbergen.bsky.social
Studying the largest insectivore🐝 animal of Europe, the Honey buzzard🦅🪶. Phenology, food availability and food use for reproduction 🪺🐥. @vogelwarte.bsky.social🦆🦢🦜🦉🐧🦤🇨🇭
https://www.researchgate.net/profile/Valentijn-S-Van-Bergen
https://www.researchgate.net/profile/Valentijn-S-Van-Bergen
Yesterday a game keeper asked me to safe a young kite that was stuck up a tree. It had one claw entangled in plastic. In eight years of ringing 1200 kites, I’ve seen every year chicks with ligaments entangled. Some 1-2 % already dies in the nest due to plastic. This one was ‘lucky’ to have fledged.
August 17, 2025 at 5:16 AM
Yesterday a game keeper asked me to safe a young kite that was stuck up a tree. It had one claw entangled in plastic. In eight years of ringing 1200 kites, I’ve seen every year chicks with ligaments entangled. Some 1-2 % already dies in the nest due to plastic. This one was ‘lucky’ to have fledged.
Spent a week in and around the forests with a nearly invisible beauty of a honey buzzards nest in a silver fir as the highlight of the week. These birds (and their social wasps) seem to have quite a good year.
July 15, 2025 at 2:21 PM
Spent a week in and around the forests with a nearly invisible beauty of a honey buzzards nest in a silver fir as the highlight of the week. These birds (and their social wasps) seem to have quite a good year.
Over the past 10 years I’ve climbed and controlled some 1000 red kite nests. Here a nest with two chicks that had an apple for lunch. Nutrient wise a useless prey but these birds bring all kinds of human refuse on their nests.
June 20, 2025 at 7:06 PM
Over the past 10 years I’ve climbed and controlled some 1000 red kite nests. Here a nest with two chicks that had an apple for lunch. Nutrient wise a useless prey but these birds bring all kinds of human refuse on their nests.
Observing nests with camera's yields quite some fascinating by-catch. Here we see a wood mouse - Apodemus sp. on a nest in a tree crown at 22m. After the birds fledged, this mouse visited it almost every night. It shows that the used habitat of this animal doesn't just consist of the forest floor.
February 10, 2025 at 2:56 PM
Observing nests with camera's yields quite some fascinating by-catch. Here we see a wood mouse - Apodemus sp. on a nest in a tree crown at 22m. After the birds fledged, this mouse visited it almost every night. It shows that the used habitat of this animal doesn't just consist of the forest floor.
For my Dutch friends: De landelijke roofvogel dag is aanstaande 22 februari in schouwburg Ogterop. Vrije inloop op een dag vol roofvogel onderzoek en verhalen. Zie hier het programma: www.werkgroeproofvogels.nl/index.php/la...
January 21, 2025 at 3:48 PM
For my Dutch friends: De landelijke roofvogel dag is aanstaande 22 februari in schouwburg Ogterop. Vrije inloop op een dag vol roofvogel onderzoek en verhalen. Zie hier het programma: www.werkgroeproofvogels.nl/index.php/la...
Some of the long-faced-red wasp combs still contained a full-grown pupa or imago so we could identify the exact species. To get the ratio of different species over this segment of the combs, we extract the DNA that is stored in the paper of the comb when the workers chewed wood into pulp.
9/9
9/9
December 7, 2024 at 9:07 AM
Some of the long-faced-red wasp combs still contained a full-grown pupa or imago so we could identify the exact species. To get the ratio of different species over this segment of the combs, we extract the DNA that is stored in the paper of the comb when the workers chewed wood into pulp.
9/9
9/9
All combs were measured and identified on species level where possible (common wasp, German wasp, European hornet) and on group level (long-faced wasps (4 species) and red wasp).
8/9
8/9
December 7, 2024 at 9:06 AM
All combs were measured and identified on species level where possible (common wasp, German wasp, European hornet) and on group level (long-faced wasps (4 species) and red wasp).
8/9
8/9
All combs were briefly frozen (to not have any small critters feeding on them), dried in a dehydrator and stored in sealed plastic bags.
7/9
7/9
December 7, 2024 at 9:06 AM
All combs were briefly frozen (to not have any small critters feeding on them), dried in a dehydrator and stored in sealed plastic bags.
7/9
7/9
Combs still containing larvae and pupae were measured/weighted on the nest but not collected as we didn’t want to steal any food from the nestlings.
6/9
6/9
December 7, 2024 at 9:05 AM
Combs still containing larvae and pupae were measured/weighted on the nest but not collected as we didn’t want to steal any food from the nestlings.
6/9
6/9
After fledging, the adults keep exclusively feeding the chicks on the nest until the fledglings are between 53 and 69 days old and the parents leave for their migration to Africa. This makes that we could follow the whole chick rearing diet without missing the post fledging part.
5/9
5/9
December 7, 2024 at 9:05 AM
After fledging, the adults keep exclusively feeding the chicks on the nest until the fledglings are between 53 and 69 days old and the parents leave for their migration to Africa. This makes that we could follow the whole chick rearing diet without missing the post fledging part.
5/9
5/9
Nests were checked every 7-14 days and empty combs were collected. We also measured the chicks and had nest camera’s but that’s all material we will focus on later, first we focus on the wasp combs.
4/9
4/9
December 7, 2024 at 9:04 AM
Nests were checked every 7-14 days and empty combs were collected. We also measured the chicks and had nest camera’s but that’s all material we will focus on later, first we focus on the wasp combs.
4/9
4/9
Honey buzzards are specialised in exploiting social wasp nests as a food source to raise their chicks. Being a long-distant obligatory migrant, they do this is a relatively short period as they are only present at the breeding grounds between mid-May and late August.
3/9
3/9
December 7, 2024 at 9:04 AM
Honey buzzards are specialised in exploiting social wasp nests as a food source to raise their chicks. Being a long-distant obligatory migrant, they do this is a relatively short period as they are only present at the breeding grounds between mid-May and late August.
3/9
3/9
In our study area in CH, we’ve collected 5459 combs between 2020 and 2024. The phase of data collection has finished, and we are working on a first paper based on this comb data. Stay tuned!
2/9
2/9
December 7, 2024 at 9:03 AM
In our study area in CH, we’ve collected 5459 combs between 2020 and 2024. The phase of data collection has finished, and we are working on a first paper based on this comb data. Stay tuned!
2/9
2/9
Some impressions of our field work of the past 5 years in which we collected data on the vespid diet of honey buzzards. To investigate the prey use by this insectivore specialist, we collected empty wasp combs from the nests during the chick rearing phase.
1/9
1/9
December 7, 2024 at 9:03 AM
Some impressions of our field work of the past 5 years in which we collected data on the vespid diet of honey buzzards. To investigate the prey use by this insectivore specialist, we collected empty wasp combs from the nests during the chick rearing phase.
1/9
1/9
Some of the long-faced-red wasp combs still contained a full-grown pupa or imago so we could identify the exact species. To get the ratio of different species over this segment of the combs, we extract the DNA that is stored in the paper of the comb when the workers chewed wood into pulp.
December 7, 2024 at 8:53 AM
Some of the long-faced-red wasp combs still contained a full-grown pupa or imago so we could identify the exact species. To get the ratio of different species over this segment of the combs, we extract the DNA that is stored in the paper of the comb when the workers chewed wood into pulp.
All combs were measured and identified on species level where possible (common wasp, German wasp, European hornet) and on group level (long-faced wasps (4 species) and red wasp).
8/9
8/9
December 7, 2024 at 8:52 AM
All combs were measured and identified on species level where possible (common wasp, German wasp, European hornet) and on group level (long-faced wasps (4 species) and red wasp).
8/9
8/9
All combs were briefly frozen (to not have any small critters feeding on them), dried in a dehydrator and stored in sealed plastic bags.
7/9
7/9
December 7, 2024 at 8:52 AM
All combs were briefly frozen (to not have any small critters feeding on them), dried in a dehydrator and stored in sealed plastic bags.
7/9
7/9
Combs still containing larvae and pupae were measured/weighted on the nest but not collected as we didn’t want to steal any food from the nestlings.
6/9
6/9
December 7, 2024 at 8:51 AM
Combs still containing larvae and pupae were measured/weighted on the nest but not collected as we didn’t want to steal any food from the nestlings.
6/9
6/9
Nests were checked every 7-14 days and empty combs were collected. We also measured the chicks and had nest camera’s but that’s all material we will focus on later, first we focus on the wasp combs.
4/9
4/9
December 7, 2024 at 8:50 AM
Nests were checked every 7-14 days and empty combs were collected. We also measured the chicks and had nest camera’s but that’s all material we will focus on later, first we focus on the wasp combs.
4/9
4/9
Honey buzzards are specialised in exploiting social wasp nests as a food source to raise their chicks. Being a long-distant obligatory migrant, they do this is a relatively short period as they are only present at the breeding grounds between mid-May and late August.
3/9
3/9
December 7, 2024 at 8:50 AM
Honey buzzards are specialised in exploiting social wasp nests as a food source to raise their chicks. Being a long-distant obligatory migrant, they do this is a relatively short period as they are only present at the breeding grounds between mid-May and late August.
3/9
3/9