Abstract
Simple SummaryScientific research is an integral part of species protection. Thanks to the use of camera monitoring during a conservation project targeting a threatened Polish population of Osprey, we discovered that the influence of natural causes of brood losses is stronger than in previous years. This would be a kind of catastrophe for the species in the whole country. We conclude that only active protection and stopping the anthropogenic causes of Osprey mortality (e.g., poaching) could stop the decline in the population and give Poland a chance to not to be red spot on the European green map of Osprey.Poland is the only European country where the Osprey population is declining due to the mortality of adult birds from poaching, which impacts not only single breeding attempts but also the Lifetime Reproductive Success (LRS) of specimens. However, what if there came an extra mortality factor in the moment of the lowest numbers of Osprey, already vulnerable in the country? In the years 2018–2020, we installed 22 trail cameras and five digital cameras (live online video feeds) on the nests. The total failure level observed in cameras (18.5%) was high. We observed, using these cameras, the extra mortality of chicks (10.7% of potentially fledged chicks) and even adult birds by unexpected predation by Northern Goshawk and White-tailed Eagle. This phenomenon is also common in the national population, as we found a total of ten cases of total losses by predators (eight or nine of them were birds of prey), including nests not covered by camera monitoring. The extra adult-predation by Goshawks means an extra drop in LRS. Those adult and chick predations are an example of exceptional catastrophic phenomena, which have been described as the direct cause of the extinction of animal populations throughout history. Only active conservation and stop poaching of the Polish population could stop the decline and save the Polish Ospreys.
Highlights
IntroductionAfter the poaching and Dichlorodiphenyltrichloroethane (DDT) catastrophe and consequent steep decline until 1970, the population has constantly increased since 1980, almost in the whole European breeding range
The Osprey (Pandion haliaetus) is one of the most widespread birds in the world [1]
We determined the causes of the mortality mainly from the traces, e.g., birds of prey nibbled on feathers, predatory mammals bit off feathers, or a bullet or bullet wound were found in poached birds
Summary
After the poaching and Dichlorodiphenyltrichloroethane (DDT) catastrophe and consequent steep decline until 1970, the population has constantly increased since 1980, almost in the whole European breeding range. In Poland, we observe the opposite situation and this country is the red spot on a green map of Ospreys in Europe. The main reason of this special situation is poaching of adult birds, especially the specimens, which use fish farming ponds as hunting grounds [4,5]. The area of the western subpopulation is concentrated around the tri-border of Lubuskie, Wielkopolskie, and West-Pomeranian Voivodship. Most Polish Ospreys breed in several areas of the Special Protection Areas (SPAs) Nature 2000 list, and only a few breed outside SPAs in Lubuskie Voivodship (W Poland) and in Romincka Forest (N-E Poland)
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