Nature today | Four years of channel research into red kites in the Netherlands
Breeding behavior of young red kites
Three youngsters from 2019 mated in 2022 and built a nest. A bird from Drenthe nested in the Achterhoek, an Overijssel bird just across the border in Germany near Winterswijk and a bird from Limburg in its native region. Only the Overijssel bird went on to lay eggs, but the egg did not hatch. The bird in the Achterhoek died just before egg laying. The birds from 2020 also partly targeted a nest. The other behaviors, together with the youngsters of the year, still see a lot of z. Two of the youngsters from 2021 have been staying in Jutland (Denmark) since the summer. Previously tagged young didn’t come nearly as far north as they were in their second calendar year. It is also remarkable that most birds that have been tagged as nestlings in the minimum of Dutch areas and therefore their native regions use them completely, with the exception of a few parts of summer Limburg and eastern Netherlands (see map). This is possible due to food scarcity in large parts of the Netherlands, where only sufficient food was available last summer.
Death of young red kites
Of the ten nestlings from 2019, three were still alive at the beginning of this year, now there are only two. Of the 11 nestlings from 2020, four were still alive at the beginning of the year, but two more died in the spring and summer. Of the seven youngsters from 2021, six were still alive at the beginning of the year, but another bird died in April. In 2022, seven youngsters will again be equipped with transmitters, two of which died in the summer. The rest are now roaming around, just as the youngsters from earlier years did in their first summer. The mortality of young birds is greater than expected and the main cause so far is it, with the caveat that for the majority of personalities the cause of death has yet to be determined. Suspicions of poisoning are high, but difficult to establish in the cases. At the moment, fourteen reed wights tagged as nestlings are still alive.
Breeding behavior and mortality of adult red kites
Additional research into terrain use and flight behavior of adult breeding red kites will be started in 2021. Last year, a total of five breeding birds were tagged in the South Limburg hills and Gelderland, including two older ones; this year a breeding female from South Limburg was added. In 2021, the young of a tagged breeding pair from Valkenburg were predated, probably by martens. In the spring of 2022, both birds returned to the nesting site. The data from the transmitters indicated that the female had no intention of using the 2021 breeding site again. Eventually the pair bond brake and both birds built a nest with a new mate. However, this separation did not appear to be the basis for greater breeding success. The female definitely went wrong in the young phase, probably due to a visit from an eagle owl hawk and it died in the egg phase in a field near Dilsen-Stokkem (B), with a strong chance of poisoning.
The male of a Gelderland couple did not return from Spain, again with suspicions of poisoning. The female did return and made a frantic effort to find a new mate, commissioning at least two nests. Breeding attempts are not forthcoming, probably due to the delay in the search for a new mate. The Limburg male from the Heerlen region raised successful young in both 2021 and 2022. The new transmitter female (2022) from the Vaals region also brooded successfully. Of the adults with transmitters, the birds from Heerlen, Vaals and Zutphen did stay in the breeding territories this summer. The adult female from Valkenburg flew to the Kassel region (D) in the federal state of Hesse in July.
Follow online: travel to the winter areas in southern Europe
The tagged young red kites from 2019-2022 are back to follow online during their migration and hibernation. The adults cannot be followed online because they use the breeding sites in the spring, which creates a risk of disturbance by unwanted visitors.
The research on young red kites continues Life Eurokite, Delta Environment ProjectsProvince of Limburg, Province of Drenthe and the Kingfisher Fund of Bird protection Netherlands. Some of the channels are sponsored by Working group Birds of prey Netherlands, Bird working group Northwest-Achterhoek, and Jeroen de Bruijn. The research into adult red kites is carried out by the Province of Limburg (breeding birds Limburg) and Vogelwerkgroep Noordwest-Achterhoek (breeding birds Gelderland).
Text: Stef van Rijn, Montagu’s Harrier – Field Birds Knowledge Center
Photos: Bas de Maat; Uwe Huchel; Rene Janssen