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Diet of adult eagle uwl during breeding season in Northwestern Türkiye

Gözütok Serdar

Polish Journal of Ecology

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2023

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Vol. 71, nr 1

27--36

EN

Published studies on the diet of the Eurasian eagle owl (Bubo bubo) in Türkiye are limited to the eastern and central parts of the country. This study presents the diet composition of a single pair of eagle owl in the breeding season in Northwestern Türkiye. In total, 91 pellets of B. bubo were collected in Bolu Province. They contained 949 prey items of 18 prey species belonging to the orders Rodentia, Eulipotyphla, and Carnivora, class Mammalia and eight species belonging to the order Passeriformes, class Aves. The owl's diet was mostly composed of rodents (94.62%). Microtus hartingi, Microtus subterraneus, and Sciurus anomalus were detected in the diet of Bubo bubo in Türkiye for the first time. In addition, a specimen of Mustela nivalis was recorded in Bubo bubo pellets for the first time in Northwestern Türkiye. Niche breadth, Shannon-Wiener, and Simpson indices were calculated and found to be 6.69, 2.23, and 0.85 respectively. The estimated species richness (Chao1) of eagle owl prey was 30.9. The average prey number per pellet was 10.42 ± 5.76. The predominant species in the diet of Bubo bubo were Microtus mystacinus, Cricetulus migratorius, and Microtus subterraneus. Detailed comparison with other eagle owl prey data collected across Türkiye is also presented.

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Diet composition of the small sandeel (Ammodytes tobianus) in the Polish part of the southern Baltic Sea

Dziaduch D.

Biuletyn Instytutu Morskiego w Gdańsku

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2018

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Vol. 33, No. 1

94--101

EN

The aim of this survey was to determine the diet composition of the small sandeel (Ammodytes tobianus L.) from coastal waters of the middle coast of Poland. The small sandeel is a fish that is only occasionally caught on an industrial scale in the Polish exclusive economic zone, but it does constitute an important food source for predatory fish, seabirds, and mammals. This species throughout the whole life feeds mostly on zooplankton. The fish for the surveys came from manual trawl hauls carried out in various seasons of the year, between November 2014 and September 2015, in the region of the estuary of the river Łupawa to the southern Baltic Sea. The surveys involved both a macroscopic examination of the stomach fullness degree of the small sandeel and a detailed analysis of its diet composition. Studies results indicated that in the course of the year, over 60% of individuals of the small sandeel had their stomachs filled with food in August, while in the early spring and late autumn their stomachs were often empty. When the samples from all analyzed months were taken into account, the diet of the small sandeel varied and consisted of 26 food components. The basis of the diet was mainly made up of Calanoida: Acartia spp. and Temora longicornis. Moreover, freshwater Cyclopoida had a high frequency of occurrence in the diet of the small sandeel throughout the year of surveys, because as organisms typical for the Lake Gardno, through which the river Łupawa flows, they also occurred in the coastal waters. In May, Harpacticoida also appeared in all analyzed individuals of the small sandeel. Only the largest small sandeels fed on fish larvae and Mysidacea. The diet composition of the small sandeel confirmed that these fish are linked with a specific habitat and do not undertake long-distance food migrations.

PL

Celem pracy było określenie składu pokarmowego tobiasza (Ammodytes tobianus L.) z wód przybrzeżnych środkowego wybrzeża Polski. Tobiasz to ryba jedynie okazjonalnie poławiana komercyjnie w polskich obszarach morskich, natomiast stanowiąca ważne źródło pożywienia dla ryb drapieżnych, ptaków morskich i ssaków. Gatunek ten w ciągu całego swojego życia odżywia się przede wszystkim zooplanktonem. Ryby do badań pochodziły z zaciągów włokiem ręcznym z rejonu ujścia rzeki Łupawy do Bałtyku południowego, prowadzonych o różnych porach roku w okresie od listopada 2014 r. do września 2015 r. Badania uwzględniały zarówno makroskopową ocenę stopnia wypełnienia żołądków tobiasza pokarmem, jak i szczegółową analizę składu pokarmowego. Wyniki badań wykazały, że w ciągu roku ponad 60% osobników w sierpniu miało całkowicie wypełnione żołądki pokarmem, podczas gdy wczesną wiosną, jak i późną jesienią żołądki często były puste. Pokarm tobiasza był różnorodny i w jego skład wchodziło 26 składników pokarmowych, biorąc pod uwagę próbki z wszystkich analizowanych miesięcy. Podstawę diety stanowiły głównie Calanoida: Acartia spp. i Temora longicornis. Ponadto słodkowodne Cyclopoida miały wysoką frekwencję występowania w pokarmie tobiasza w całym roku badań, ponieważ jako organizmy charakterystyczne dla Jeziora Gardno, przez które przepływa rzeka Łupawa, występowały również w wodach przybrzeżnych. U wszystkich przeanalizowanych osobników tobiasza w maju pojawiły się także Harpacticoida. Jedynie największe tobiasze odżywiały się larwami ryb i Mysidacea. Skład pokarmowy tobisza potwierdził, że ryby te związane są z określonym siedliskiem i nie wykazują dalekich wędrówek żerowiskowych.

3

Diet composition of the Morocco dentex : Dentex maroccanus Valenciennes, 1830 (Teleostei: Sparidae) in the central Turkish Aegean Sea

Bayhan B., Sever T. M., Heral O.

Oceanological and Hydrobiological Studies

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2017

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Vol. 46, No. 2

133--139

EN

This study examined the stomach contents of 230 individuals out of 439 samples obtained from commercial fishermen between January 2013 and March 2014 from a trawler using trawl bags with a full cod-end mesh size of 44 mm. It was found that 216 samples were full and the stomach fullness index was estimated at 93.9%. The varying diet composition of the species was determined by estimating the percentage numerical composition (N%), frequency of occurrence (F%), gravimetric composition (W%) and the index of relative importance (IRI%). Diversity (Shannon index), richness (Margalef index) and similarity (Bray-Curtis index) of the catches in different seasons were calculated using the Biodiversity Professional (Version 2) software. Three major groups were identified in the catches: Crustacea, Mollusca and Teleostei. At least 17 different prey groups were identified. With regard to the diversity of consumed prey, the winter (1.204), autumn (1.079) and spring (1.000) seasons were characterized by a medium level of diversity, summer (0.699) – by a low level of diversity. However, the richness of prey does not show seasonal differences. As indicated by the Bray-Curtis index, the highest similarity between the prey groups was observed between the autumn and winter seasons, at 81.61%.

4

Dietary overlap of co-occurring Barn owl, Tyto alba Scopoli and Spoted eagle owl, Bubo africanus Temnick in urban and rural environments

Kopij G., Symes C. T., Bruyns R.

Polish Journal of Ecology

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2014

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Vol. 62, nr 4

801--805

EN

Diet of co-occurring Barn Owl and Spotted Eagle Owl has been studied by means of pellet contents analysis in urban and rural environments in the Highveld of South Africa. In urban environment, diet of both owl species was dominated by murid rodents (mainly Otomys, Mastomys and Rhabdomys). In rural environment, Barn Owl diet was also dominated by murid rodents, but in the diet of the Spotted Eagle Owl higher proportion of birds and non-murid rodents was recorded. Although in the rural environment the breadth of diet niche was wider in Spotted Eagle Owl (DB = 35.41) than in Barn Owl (DB = 12.67), there was almost total dietary overlap (DO = 0.98) between these two co-occurring owl species. For contrast, there was only slight food niche overlap (DO = 0.12) between these owl species co-occurring in the urban environment, but the diet breadth here was also wider in Spotted Eagle Owl (DB = 29.02) than in Barn Owl (DB = 17.90). In the urban environment diet breadth of the Spotted Eagle Owl is, therefore, slightly wider than in rural environment, while in the case of the Barn Owl the reverse is true. Probably there is lower abundance of available prey in urban and rural areas in the Highveld, in comparison with more natural habitats. This may force both species to resort to a more diverse diet to meet their energy requirements. Both species show, therefore, high plasticity of foraging.

5

The effect of urbanization on the diet composition of the Tawny owl (Strix aluco L.)

Grzędzicka E., Kus K., Nabielec J.

Polish Journal of Ecology

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2013

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Vol. 61, nr 2

391--400

EN

In recent years, developing urban areas have affected food abundance and the feeding grounds of birds. The article contains analysis of the Tawny owl’s diet during four years (2006–2009) from different types of the urbanized area: city, town (much smaller than city) and countryside – based on 356 pellets with 726 prey items. The main group of victims was Rodentia, common were also Apodemus agrarius and Apodemus sylvaticus. Other important groups in the diet were: Microtidae (especially species Microtus arvalis) and Aves. As a generalist, Tawny owl fits the diet to the actual resources in a very flexible way. The main goal of the present work was to describe the food composition variability of the Tawny owl along with the degree of urbanization. Percentages of Microtus arvalis, Micromys minutus, Talpa europaea depended on the urbanization level, while Apodemus flavicollis, Insecta and Amphibia were related to the distance to nearest city centre. The study has shown that the diet of the Tawny owl has been changing along the urbanization gradient. It confirms earlier findings on high plasticity of foraging of this species in urbanized landscape.

6

Diet composition of herring (Clupea harengus L.) and cod (Gadus morhua L.) in the southern Baltic Sea in 2007 and 2008

Dziaduch D.

Oceanological and Hydrobiological Studies

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2011

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Vol. 40, No.4

96-109

EN

cod, were studied in some regions (mainly Gdańsk and Bornholm Basins, and the Polish coast) of the southern Baltic Sea in 2007 and 2008. Herring is the dominant zooplanktivorous species in the ecosystem of the Baltic Sea, but apart from mesoplanktonic organisms it also eats macroplanktonic and benthic species in considerable amount. The diet of cod consists of fish and crustaceans from pelagic, hyperbenthic and benthic habitats. The feeding preferences of fish indirectly reflect changes in the whole food chain in the Baltic Sea. This research focuses specifically on these invertebrate species, which are eliminated from the environment by most of the ichthyofauna of this region. The aim of this research is to examine the role of invertebrate organisms belonging to Crustacea in the diet of herring and adult cod to supply updated results about feeding of these fish as little data have been collected since the 1990s. The present study is a preliminary survey and results can not be considered conclusive. The restricted numbers of analyzed stomachs of fish and selected seasons of the year addressed in this paper are a starting point for further studies with a larger scope. In this study, 20 to 90% of herring had empty stomachs. Mesozooplankton dominated the diets of small and large herring. Mysidacea, which were historically important prey for herring, are now scarce and have been replaced by planktonic Amphipoda. In the case of cod, consumption of Mysidacea has never been as low as in this study. As for other invertebrate prey, the benthic isopod Saduria and Crangon shrimp achieved the highest amount by number and weight. These results show distinct changes in diet when compared to previous investigations and require verification at a larger spatial scale.

7

Towards the optimal foraging strategy : is seasonal shift in the diet of Cormorants Phalacrocorax carbo (L.) in a dam reservoir the effect of water temperature or size pattern in fish assemblages?

Gwiazda R., Amirowicz A.

Polish Journal of Ecology

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2010

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Vol. 58, nr 4

783-792

EN

According to optimal foraging theory the prey choice strongly affects the benefitcost ratios. Predators search prey giving the highest benefit and costs of all components of predation (i.e. prey search, encounter, pursuit, capture, and handling) may be considerably reduced if the prey is more available. The study on Cormorant diet and the species composition of prey fish assemblages in the Dobczyce Reservoir (area 985 ha, submontane, eutrophic reservoir in Southern Poland) in spring (May-June) and in autumn (Oct-Nov) showed differences in the food composition and the prey size affected by seasonal changes in fish availability. The diet of Cormorant included eleven fish species and the dominant species in the food was roach in spring (72%) and roach and perch in autumn (49% in total). Roach and perch had the highest share in prey assemblages too (56% in spring, and 53% in autumn). Significant preference toward roach in spring was found. The share of roach and perch did not changed seas seasonally and could not explain the change in the composition of Cormorant diet. The range of the total length (LT) of fish in Cormorant diet was 3.5-35.2 cm. Diet consisted of distinctly smaller fish in autumn. Relative number of small fish was ca 3 times greater in this period compared to spring. Weighted mean of fish TL in prey assemblage was 20.0 cm for roach and 12.5 cm for perch in spring, and 11.8 and 8.1 in autumn, respectively. The proportion of average weight of roach (W = 0.004074 LT[^3.334]) to that of perch (W = 0.005779 LT[^3.260]) was greater in spring (4.1:1) than in autumn (2.9:1). Probably it can explain the diet shift in autumn. The switch to smaller but more abundant fish in autumn was not related to temperature but to fish availability which reduced the cost of searching and the prey may be easily found.

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Small mammals in the diet of the Tawny Owl (Strix aluco L.) in Central European Lowland

Żmihorski M., Balciauskiene L., Romanowski J.

Polish Journal of Ecology

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2008

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Vol. 56, nr 4

693-700

EN

We analysed the variation of small mammal species composition in the Tawny Owl Strix aluco L. diet in forest habitats of Central European Lowland. We used published and unpublished materials from forest-dominated landscapes in Lithuania (n = 7 locations), Poland (n = 8) and East Germany (n = 1); marginal localities were ca. 870 km from each other. We recorded that in Central European Lowland the proportion of Arvicolidae in the Tawny Owl diet significantly increased, while that of Muridae decreased toward north-east. The proportion of less common rodent species (including Gliridae and Sicita betulina Pallas) in the diet also increased significantly toward NE. We did not record any trend of small mammals diversity along the analysed transect. We suggest that the change of Arvicolidae to Muridae ratio toward north-east can be caused by the replacement of mice with boreal vole species in small mammal community. Small mammal diversity in Central Europe is subject of discussion.