Monitoring of griffon vulture

The monitoring of the griffon vulture population in the Eastern Rhodope Mountains has been carried out since 1988 with the following objectives:

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determine the number of birds;

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determine the number of pairs, and the number of nesting pairs;

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discover new nesting sites;

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determine the age structure of the population;

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determine the nesting and reproductive success of the individual colonies and of the population as a whole;

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determine the individual territories of the birds and the spatial ecology of the species.

© Franz Robiller/Griffon vulture

Four methods are used:

Roost monitoring

The monitoring is carried out in November–December, and the count takes place on the same day for all teams. All cliffs known to be used as resting and nesting sites by the vultures are inspected. Each location is monitored by one team that must be positioned at a distance of at least 300 metres. The count is done with a spotting scope and binoculars. Every hour the weather conditions are noted down. The number of vultures that roost on the cliff is recorded every 15 minutes. If a bird takes off, the direction in which it flies away, is noted down. The birds are divided into several categories according to their age. During the monitoring the number and age of other raptors and corvids that use the same cliffs for roosting and resting are also noted down. The monitoring starts at 2 pm and ends 30 min. after sunset.

© Dimitar Gradinarov
© Bogdan Boev / Griffon vulture

Monitoring of supplementary feeding sites

The supplementary feeding sites are monitored at least twice a month all year round. The monitoring is done with a spotting scope and binoculars from the feeding site to avoid disturbance. The weather conditions are noted down on the hour. The observation starts after the food is brought out and ends when it is consumed. Important additional information for this type of monitoring includes the type of food, its origin, its weight, time of delivery to the feeding site. The number of feeding vultures is constantly monitored, together with the age structure of the group. Marked birds are noted down; the observer records their age, the type of mark (wing tag, ring and/or transmitter), its colour and number, its position (right/left wing/leg). For the black vultures the direction from which they arrive, as well as the direction in which they fly away after feeding are also recorded. The collected data are filled in in a standardized form for feeding site monitoring. In addition to this type of monitoring photo traps and cameras are installed that contribute for more detailed data collection, and can be used in times of low visibility from the observation point and/or in the cases when a feeding is not being monitored in person.

© Bogdan Boev / Griffon vulture

Monitoring of nesting cliffs

The monitoring is carried out 4 times every year in February–March. All known nesting sites are visited. The data collected include (chronologically): total number of pairs; number of pairs on nests; age; number of incubating pairs; number of hatched young; number of successfully raised young. Each occupied nest is mapped and photographed and it is entered in the specialized data base under an individual number. The data allow us to monitor changes in population numbers, the rate of increase and the nesting success (ration of number of young that left the nest successfully against number of incubating pairs), and to compare these values with populations in other countries.

Research on the movement of the griffon vulture

Since 2016 the BSPB carries out research on the movements of griffon vultures, the individual territories, and the sites used for feeding, resting and roosting. This type of monitoring is done with GPS transmitters. Until 2021 32 birds of different ages have been tagged. Thus we collect substantial data about the ecology and the spatial distribution of the species, as well as for the identification of the main threats.

All observations from the monitoring activities are collected in the BSPB’s internet-based data base SmartBirds.

Black vulture monitoring

The monitoring of black vultures in the Eastern Rhodope Mountains, Bulgaria, has the following objectives:

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determine the sites for feeding and resting;

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discover pairs, nesting territories and flight corridors;

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discover new nesting sites;

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determine the age structure of the population.

© Stefan Avramov/Black vulture

To achieve that we use the following methods:

Research of the vultures’ movements through observation from stationary observation points

This type of monitoring aims at determining potential sites for roosting and resting, and at studying the main flight corridors of the black vultures from their nesting colony in Dadia, Greece, to the feeding sites on the Bulgarian side of the Eastern Rhodope Mountains. For the purpose we choose spots at a higher altitude that provide good visibility to the surrounding area. The monitoring is done twice monthly from all chosen spots in the period May–December. The observation points should be accessible in bad weather too. The monitoring is done during the day when the weather permits it (no monitoring in fog/heavy rain) by experienced observers. The records for all observed raptors include: number of birds, age, altitude, direction and type of flight (gliding, soaring, active), behaviour. If the bird is marked, the type of marker (ring, wing tag, transmitter) is noted down, together with the colour and the number, and the position (right/left leg/wing). The behaviour should be described in detail. Data are collected for other bird and mammal species that are observed.

Monitoring of black vultures on the supplementary feeding sites

Observation on the supplementary feeding sites is carried out at least twice a month all year round for the particular territory. Monitoring is done with a spotting scope and binoculars at the feeding site to avoid disturbance. The weather conditions are noted down on the hour. The observation starts after the food is brought out and ends when it is consumed. Important additional information for this type of monitoring includes the type of food, its origin, its weight, time of delivery to the feeding site. The number of feeding vultures is constantly monitored, together with the age structure of the group. Marked birds are noted down; the observer records their age, the type of mark (wing tag, ring and/or transmitter), its colour and number, its position (right/left wing/leg). For the black vultures the direction from which they arrive, as well as the direction in which they fly away after feeding are also recorded. The collected data are filled in in a standardized form for feeding site monitoring. In addition to this type of monitoring photo traps and cameras are installed that contribute for more detailed data collection, and can be used in times of low visibility from the observation point and/or in the cases when a feeding is not being monitored in person.

All observations from the monitoring activities are collected in the BSPB’s internet-based data base SmartBirds.

© Sv. Spasov/Black vulture

Egyptian vulture monitoring

The BSPB started carrying out systematic monitoring of the Egyptian vulture in Bulgaria in the beginning of the 21st century. It has the following objectives:

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identify all the existing pairs of Egyptian vultures in Bulgaria;

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determine the number of young and non-breeding birds;

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determine the nesting success and the reasons for chick loss;

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provide safety for the young vultures in the period when they leave the nest.

© Franz Robiller/Egyptian vultures

Monitoring of breeding pairs

All nesting cliffs that were used by the species in the previous breeding season, as well as nesting territories used in the past, or territories that are suited for occupation by new pairs, are visited. Observations are carried out at least 3 times in March–August. Thus the number of occupied nesting territories is determined, along with the age of the partners in the pair, the number of hatched young, and subsequently – the number of young that are raised successfully. In August intensive daily monitoring is carried out together with nest guarding for some of the nests in order to guarantee that the young Egyptian vultures leave the nests without trouble.

Photo and video monitoring of nests

Photo traps and video cameras are also used for the monitoring of nesting pairs. The devices are installed in the nest or close to the nest. This innovative methodology allows us to monitor closely the breeding process from beginning to end and to identify causes of death for the young vultures in the early stages of their development, as well as threats (for example, presence of predators or competitive species). We monitor the survivability of the partners in the pair, too.

Yordan Hristov

Dalmatian pelican monitoring

The Dalmatian pelican monitoring in Bulgaria has the following objectives:

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determine the number of nesting pairs;

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determine the number of Dalmatian pelicans that live in Bulgaria;

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determine the nesting and reproduction success of the individual colonies and of the population as a whole.

© Sv.Spasov/Dalmatian pelican

Three methods are used:

Spring count of pelicans in Southeastern Europe

The spring count of pelicans in Southeastern Europe was launched in 2016; it is carried out every year in the beginning of May. The objective is to collect data about the numbers and distribution of the Dalmatian and the white pelican in Bulgaria, Greece, Romania, Ukraine, Turkey, North Macedonia, Montenegro and Albania. The count is organized and coordinated by the Society for the Protection of Prespa, Greece. The BSPB is the coordinator for Bulgaria. During the count the wetland areas where the pelicans might be observed (lakes, marshes, reservoirs, sand spits and islands on the Danube River, etc.) are visited. The count starts in the afternoon; its aim is to record the number of roosting pelicans. The count is done with spotting scopes with a recommended magnification 20–60 x and binoculars 10×42, 10×50.

© Bogdan Boev/Dalmatian pelican
© Petar Yankov/Dalmatian pelicans

Monitoring of the spring and autumn migration of the Dalmatian pelican in key wetlands in Bulgaria

Observations are carried out twice per month from late January till late April and between early July and early December. Only key territories for the species are visited – the Danube River, the Burgas Lakes, the big reservoirs in Southern Bulgaria, etc.

Dalmatian pelicans

Monitoring of wintering Dalmatian pelicans

This monitoring is carried out within the traditional mid-winter waterfowl count that takes place every year in mid-January. Teams of experts and volunteers visit all the wetlands in the country and collect data about the wintering species of waterfowl, Dalmatian pelicans included.

Dalmatian pelicans

Monitoring of the nesting colonies

In Bulgaria the Dalmatian pelican nests in Srebarna Lake, and in Peschina and Martvo Marshes too. The two marshes are located on Persin Island, within the boundaries of Persina Nature Park. The observations on the nesting colonies are carried out every month in the period February–July. Records include (chronologically): number of incubating pairs; number of hatched young; number of successfully raised chicks. Thanks to the collected data we can detect changes in the numbers of the population, the rate of its increase, the nesting success (average number of young per pair), and compare the results with populations from other countries.

Graph of the population and the nesting success in Persina National Park since 2016

 

Year
Breeding pairs
Fledged pelicans
2016
7
10
2017
4
5
2018
9
9
2019
24
30
2020
30
40

Monitoring of the red-breasted goose

Monitoring of the red-breasted goose started in the mid-1990s and has been going on without major changes ever since. Only recently some elements have been upgraded and developed further.

The target area of the monitoring initially included the region of coastal Dobrudzha (Northeastern Bulgaria), chiefly around Shabla and Durankulak Lakes but subsequently it has been expanded to include the Burgas Lakes and the Svishtov-Belene Plain too.

The monitoring is carried out in the period November–March, the months when the geese come to winter in Bulgaria. In the aforementioned period, counts are carried out every two weeks – roughly 10 to 12 counts per winter season.

The main objective of the monitoring is to determine the numbers and the dynamics of the wintering red-breasted geese in the country. We collect data about the other species of wintering geese too.

© Mladen Vasilev/Red-breasted goose
© Chavdar Nikolov/Red-breasted goose

The information that we receive as a result of the monitoring includes:

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dynamics of the numbers of wintering geese;

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period of wintering for the geese in Bulgaria;

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species structure of the wintering geese populations.

Additional data that can be planned for collection if the conditions allow it include:

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age structure of the red-breasted goose;

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physical state of the birds based upon abdominal fat index;

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spatial distribution of flocks of grazing geese and conditions at the feeding habitats.

Data from this monitoring form the basis for assessing the global population of the red-breasted goose and its conservation status. A portion of the counts are coordinated with our colleagues in Romania and Ukraine in order to provide a more complete picture of the numbers of the species.
© Chavdar Nikolov/Red-breasted goose

The methodology of the count is to count the roosting geese early in the morning upon take-off from the lakes and the other roosting sites (coastal bays in the Black Sea). Stationary observation points are used for the count, as they provide good visibility and field of view for the person doing the count. In case there are more geese and more roosting sites in the coastal area of the Black Sea, additional observation points are created. There should be one person per observation point; on OPs with a higher density of roosting geese there should be two people – one takes notes. In case of really big densities there should be more than 2 people (3–5); one person counts only the red-breasted geese in the flocks, and the others count the flocks in their entirety.

A standardized form is used for the count. Since 2013 the data are entered in the digital platform SmartBirds Pro too. The count takes place during the weekend because of the volunteers participating. The counters take their positions before sunrise; the observations continue until all geese have left the lake/until no more geese arrive from the sea/the Danube.

© Mladen Vasilev/Red-breasted goose

Observations are done with binoculars and a spotting scope with magnification over 30/40 x so that the species can be identified within the mixed flocks that fly at a distance from the counter.

Data about the age structure, abdominal profile, occupied feeding grounds are collected after the morning count is completed – when the geese graze on the fields of winter wheat. Usually the presence of rarer species, such as lesser white-fronted goose, bean goose, barnacle goose, is recorded at this stage. Data collection is highly dependent on disturbance in the area; the flocks of grazing geese are approached most easily for an assessment of their age structure and abdominal profile (key for the data collection) after the end of the hunting season.

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