Issue 2023-2

Ornis Polonica 2023, 64: 81–106

An increase in the Pomeranian population of the Pygmy Owl Glaucidium passerinum against the backdrop of the situation of the species in Poland and Europe

Arkadiusz Sikora, Mateusz Gutowski, Damian Ostrowski, Urban Bagiński, Małgorzata Bagińska, Grażyna Jaszewska, Michał Przystański, Michał Barcz, Miłosz Kowalewski

Abstract: In the 21st century, an increase in the breeding population and territorial expansion of the Pygmy Owl Glaucidium passerinum in Pomerania has been recorded. In the late 1990s, the first territorial male was recorded, and since 2006 the species has been recorded annually. In years 2016–2022, its occurrence was revealed in 15.8% of squares (N=80) out of 507 10 × 10 km plots in the region, being the most common in the central part of Pomerania (30.6% of squares with the species present; N=144), followed by Gdansk Pomerania (14.0%; N=164) and the least numerous in the western part (6.5%; N=199). The Pygmy Owl was most abundant in the lake districts in the southern part of the region, and the population in Pomerania was estimated at 250–350 territories. The most important Pygmy Owl refuges in the region are the Człuchów Forests (50–60 territories), SPA Forest at Gwda River (40–50 territories, including 20–25 territories in the Pomeranian Ornithological Region), SPA Tuchola Forest and Forest at Drawa River (15–25 territories each), and SPA Słupia Valley and Wielki Sandr Brdy (15–20 territories each). In years 2020–2022, the average density in the 9 plots was 1.7 ter./10 km2 of total area (range 0.4–3.0) and 1.9 ter./10 km2 of forest area (0.4–3.2). Of the 71 breeding Pygmy Owl hollows in the Pomerania, the majority were detected in fresh mixed coniferous forest (31.0%) and mixed swamp coniferous forest (26.7%). In the most important refuge – Człuchów Forests – the Pygmy Owls most often inhabited forests with strong humidity (64.3%). Nesting hollows were located mainly in Scots pines Pinus sylvestris (63.0%) and European spruces Picea abies (20.5%) and less abundantly in oaks Quercus sp., birches Betula sp. and alders Alnus sp. Hollows in living trees predominated (76.7%), less frequently in dead (13.7%) and dying trees (9.6%). Scots pine was by far the most dominant species (84.5%) in the Pygmy Owl’s breeding habitat. European spruce was important as a co-dominant species (46.5% of breeding sites), and was present in the undergrowth in 78.9% of the sites. In Pomerania, Pygmy Owls nested in forest divisions where the age of stands ranged from 59 to 199 years (mean 120 years; N=71), with a clear preference for older age classes. Based on the latest data provided in this publication, the Pygmy Owl population in Poland was estimated at 1,900–2,600 territories. The Pygmy Owl population in Człuchów Forests constitutes approx. 2.4% of the national population, in SPA Forest at Gwda River there is 2.0% of the national population, in SPA Tuchola Forest and Forest at Drawa River, in SPA Słupia Valley and SPA Wielki Sandr Brdy there is 0.9% each. The Człuchów Forests area is currently the most important Pygmy Owl refuge in Pomerania and for that reason, it qualifies as a national IBA refuge and a Natura 2000 SPA.

Key words: increase of abundance, distribution, Glaucidium passerinum, Pygmy Owl, habitat, protection, IBA, Natura 2000 SPA, Pomerania


Ornis Polonica 2023, 64: 107–118

Growth rates and ageing of the Caspian Gull Larus cachinnans chicks based on biometric traits

Marcin Przymencki, Klaudia Litwiniak, Magdalena Zagalska-Neubauer, Joanna Pomorska-Grochowska, Paweł Grochowski, Grzegorz Neubauer

Abstract: Knowing the growth rate of chicks is important in ecological and evolutionary studies, since it allows to determine their age. In this article, we analysed the growth rate of chicks of the Caspian Gull Larus cachinnans for the first time for the species and we present a method of age estimation based on biometric measurements. The data were collected in 2005 and 2007 at Włocławek Reservoir (C Poland) and 2019–2020 at Mietków Reservoir (SW Poland). A total of 275 chicks were captured and ringed, and 150 of them were recaptured and measured more than once (in total 546 captures). During each capture, four biometric traits were taken: total head length (DCG), tarsus length (DT), bill height at the gonys (WD), and body mass (MA). Chicks’ average measurements at hatching were: DCG – 47 mm, DT – 24.2 mm, WD – 7 mm, MA – 55.1 g. These traits on the 35th day of chicks’ life, i.e. approximate fledging time, reached on average: DCG – 118.7 mm, DT – 76 mm, WD – 14 mm, MA – 994.7 g. DCG, WD, DT grew rather uniformly until reaching relatively stable asymptote, only the MA growth curve had a sigmoid shape. The average growth rate of traits (except WD) initially increased and then slowed down and was, respectively: DCG – 1.99 mm/day, with a peak on the 7th day of life (3.1 mm); DT – 1.44 mm/day, the highest increase was recorded on the 10th day of life (3.1 mm); WD – 0.2 mm/day, with a tendency to decline over time. Chicks’ MA was increasing exponentially until the 10th day of their life and the mean MA increase reached 26.1 g/day. The highest MA increase was recorded on the 16th day of chicks life (48.4 g/day). The data characterize the growth rate of Caspian Gull chicks and provide a valuable tool for estimating their age, and thus allow for more precise fieldwork planning in gull breeding colonies. This offers the possibility to reconstruct the approximate date of hatching and to obtain information on breeding phenology in a colony. The MS Excel spreadsheet with formulas for calculating the age of the chick based on the two most useful measurements in determining the age (DCG and MA) was made available for download (Appendix 1 to this work, at the website).

Keywords: Caspian Gull, Larus cachinnans, chicks, growth rate, ageing

Appendix 1


Ornis Polonica 2023, 64: 119–128

Decline in the population of the Syrian Woodpecker Dendrocopos syriacus in the Krakow agglomeration

Łukasz Kajtoch, Bartłomiej Kusal

Abstract: The Syrian Woodpecker Dendrocopos syriacus, species listed in Bird Directive of European Union, is present in Poland for almost half a century. After a period of expansion, there was a regress of the rural population in its core range in the SE part of the country. This species is widespread in cities of southern, eastern and central Poland, but the knowledge on urban populations is limited. This results in only populations of the agricultural landscape being protected within the Natura 2000 network in Poland.. This study compares the status of the Syrian Woodpecker population in the Krakow agglomeration between 2012–2015 and 2021. Within that period the abundance of the species decreased by 50% (from c. 21 to 12 sites in three examined plots). At the same time, an increase in the share of mixed pairs with the Great Spotted Woodpecker D. major and pairs formed by hybrids was observed. The decline in the abundance was probably related to the loss of favourable habitats (woodlands and orchards). Competition with the Great Spotted Woodpecker, which increases in number in the country, and hybridization between these species may also have had an impact on territory disappearance. The decline of the Syrian Woodpecker in south-eastern Poland may contribute to its becoming endangered in the future. It is advisable to take into account the species protection requirements in the spatial development planning of urban areas (maintaining and reconstructing preferred woodlots), and the implementation of population monitoring programmes.

Key words: Syrian Woodpecker, Dendrocopos syriacus, Kraków, decline, threats


Ornis Polonica 2023, 64: 129–154

Rare birds recorded in Poland in 2022

Komisja Faunistyczna


Ornis Polonica 2023, 64: 155–157

The first record of the Black-throated Accentor Prunella atrogularis in Poland

Marzena Prokop, Tadeusz Stawarczyk


Ornis Polonica 2023, 64: 158–159

Wilniewczyc P., Szczepaniak W., Przybylska J., Maniarski R., Wachecki M., Dudzik K. 2022. Ptaki Kielc. Towarzystwo Badań i Ochrony Przyrody, Kielce. ISBN 978-83-963072-0-0

Tomasz Janiszewski

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