@misc{Goszczyński_Jacek_Metody_1972,
 author={Goszczyński, Jacek},
 editor={Polska Akademia Nauk. Komitet Ekologiczny},
 copyright={Creative Commons Attribution BY 3.0 PL license},
 address={Warszawa},
 howpublished={online},
 year={1972},
 language={pol},
 abstract={A discussion is given of methods of studying the food of predatory birds and mammals. The review made of methods used, from the aspect of their suitability for investigating food links in the predator-prey system, led to the conclusion that the majority of them are only of an indicatory character.Results of analysis of pellets and excrements presented from the aspect of frequency of occurrence may be of assistance in tracing seasonal changes in diet, but it is difficult to reach conclusions on the basis of this method as to the real proportions of any one food, since degree of assimilation of the various components of food is different. There must be considerable error in defining diet from connections of remains of food left near nests or burrows of predators, or from analysis of their food stores, on account of the difference in the degree to which prey is utilized. It is also impossible to obtain a reliable picture of predators' diet from studies made by winter tracking, since not all the animals caught can be identified. Visual observations of food obtained give only an approximate idea of predators diet. In yiew of the above objections the following methods are the most suitable, from among many others, for evaluating the food of predtory birds: the percentage by weight, compared on the basis of pellets and direct data on the diet of nestlings, obtained by hooding young birds or by covering nests with a net. In the case of predatory mammals it is essential, when examining their diet on the basis of analysis of excrements, to introduce calculations describing the degree of assimilation of a given food component. The method of percentage by weight cannot be applied on account of difficulty in defining the number of prey consumed when examining the food of predatory mammals. Analysis of the contents of alimentary tracts in both winged and four footed predators can form a basis for listing, diets if there is no likelihood that some of the components may be over -or under -estimated on account of the time at which the predator was shot or the rate of passage of the food through the alimentary. It is only possible to define the role of predators in ecosystems and their effects on the population of their victims after the correct method for esitimating their food has been found. The author therefore suggests that breeding experiments should be undertaken on a wider scale, permitting of working out and perfecting methods, with parallel studies on the food requirements of predators.},
 type={Text},
 title={Metody badania pokarmu drapieżnych ptaków i ssaków},
 URL={http://rcin.org.pl/Content/144936/PDF/WA058_104809_P3259-18_Eko-Pol-B.pdf},
 volume={18},
 number={4},
 journal={Wiadomości Ekologiczne},
 publisher={Państwowe Wydawnictwo Naukowe},
 keywords={nutrition, predator-prey systems, birds of prey, predatory birds, Strigiformes, Accipitridae, Carnivora, carnivores},
}