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Decline of Common buzzards

logos ENSurprising results were obtained in the second year of the study. The year 2016 turned out to be a bad year for mice which is reflected by fewer Common buzzard breeding pairs with fewer eggs and nestlings dying of starvation in their nest (for new videos also see below). This is shown in the following video that aired on NDR:

Schleswig-Holstein Magazin "Sorge um Bussard-Nachwuchs" (June 2016; video in German)

The results of the first study year were also part of a brief documentary that was shown on TV (NDR):

Der Wipfelstürmer (December 2015; video in German)

What is this project about?

In 2014 and 2015 the breeding population and success of the Common buzzard was investigated for two larger study areas in the region of Schleswig for which previously recorded data from prior decades was available. Thereby a decline in the Common buzzard population was detected that had reached a level of a third of the population recorded at the turn of the millennium. One possible cause for this decline, next to conversion of agricultural lands (from grazing to corn production for biogas plants) and mortality caused by wind turbines, could be the detected low possibility of nestling survival.

Since April 2015 BioConsult SH is investigating possible causes for the decrease in breeding success in a three-year project. Next to an ongoing breeding population monitoring and a determination of the brood and clutch size, video cameras are being used to monitor buzzard nests and to test the following hypotheses that might be explanations for the low breeding success:

1. change of land use with a decline in the numbers / a worsened reachability of the main prey field vole

2. predation of young birds (Eagle owl, goshawk, mammals) in the nestling period

3. low hatching success (caused by e.g. toxins)

Per breeding season ten video cameras are positioned at buzzard nests. These cameras enable a continuous recording of the nestling period (from hatching to fledging). Using this approach, the hypotheses mentioned above can be tested by recording the following breeding biology data:

1. species, mass of food items and timing of feeding,

2. cause and time of chick disappearance, especially when predation occurs

3. determination of the chick-egg-ratio

The images recorded by the camera are transmitted via a cable that is fixed to the tree trunk into a crate on the ground that contains a power and a recording unit.

camera and crate


Videos 2016 (second study year)

In the following video a goshawk attacks two Common buzzard nestlings in their nest and eventually takes away one (sequence: "2016 Prädation Habicht"). This is the only recorded attack by a goshawk in 2016, while another nestling was taken by an Eagle owl (not shown).

Food supply for the young Common buzzards was scarce, because 2016 was a bad year for mice. In the following video the wet and freezing nestlings quarrel about a mouse. One of the nestlings fends off his siblings and eventually feeds on the mouse alone (sequence: "2016 Futterstreit").

Two hours later the weakest bird in the nest has died of starvation and falls out of the nest (sequence: "2016 Kücken fällt aus dem Nest"). In 2016 a total of eight nestlings died of starvation in the monitored nests. In 2015 no nestling had died of starvation.

Videos 2015 (first study year)

In this video a young Common buzzard is attacked and killed by an Eagle owl in its nest. The adult bird behaves very passively during the attack and does not display any behaviour to chase off the owl. The Eagle owl appears at about 0:18. Later on (at about 1:45) the adult Common buzzard is driven out of the nest. The second young bird is taken from the nest at a later point (see video: 'Prädation Jungvogel 2').

In this video the second young Common buzzard is taken from the nest by the Eagle owl (at about 0:33). This video was recorded after the video 'Prädation Jungvogel 1' (see above).


Results:

Grünkorn, T.
Projekt Ursachenforschung zum Rückgang des Mäusebussards im Landesteil Schleswig
Jagd und Artenschutz 2016 p. 91-94
Download documentExternal Link

Grünkorn, T.
Ursachenforschung zum Rückgang des Mäusebussards in Schleswig-Holstein
148th Annual Meeting of the “Deutsche Ornithologische Gesellschaft”, Konstanz, Germany (2015)
Download document

Grünkorn, T.
Projekt Ursachenforschung zum Rückgang des Mäusebussards im Landesteil Schleswig
Jagd und Artenschutz 2015 p. 94-97
Download document

Contact:

Thomas Grünkorn

Thomas Grünkorn