Ornis Svecica https://journals.lub.lu.se/os <p><strong>Ornis Svecica</strong> is an online scientific journal issued by BirdLife Sweden. All contributions are published as open access, available to anyone, and with no publication fee for the authors. The aims and scope of the journal are to provide a forum for full-length or short original research reports, including descriptive ones, and reviews, communications, debate, and letters concerning all fields of ornithology. Ornis Svecica publishes contributions irrespective of the geographic origin of authors and subject, and we welcome submissions not only from professional researchers but from laymen as well. We assume a particular responsibility to offer a process and a forum for the latter, and encourage their submission of results and ideas. The journal language will be English or Swedish with a comprehensive summary in the other language (assistance is offered to authors with insufficient knowledge in the language for the summary).</p> BirdLife Sweden en-US Ornis Svecica 1102-6812 <p>The copyright of each contribution belongs to the author(s), but all contributions are published under a Creative Commons license, so that anyone is free to share and reuse the contribution as long as the copyright holder is attributed.&nbsp;</p> A review of mass concentrations of Bramblings Fringilla montifringilla: implications for assessment of large numbers of birds https://journals.lub.lu.se/os/article/view/22031 <p>Mass concentrations of birds, or the lack thereof, is a phenomenon of great ecological and domestic significance. Apart from being and indicator of, e.g., food availability, ecological change, and population size, it is also a source of conflict between humans and birds. By attracting the attention of the public—either as a spectacular phenomenon or as an unwelcome pest—they also form the public perception of birds and their abundance. In the context of the mass concentration of Bramblings <em>Fringilla montifringilla</em> in Sweden during the winter 2019–2020, this work reviews the literature on this striking phenomenon. I found that winter roosts amount to about one million birds per hectare of roost area, but the variation between reports is significant. There is support for roosts of up to around 15 million Bramblings, but much larger numbers are frequently cited in the literature. I discuss difficulties related to the assessment of mass concentrations, and argue that reports of very large numbers should always be carefully scrutinized.</p> Tomas Svensson Copyright (c) 2021 Tomas Svensson http://creativecommons.org/licenses/by/4.0 2021-04-24 2021-04-24 31 44–67 44–67 10.34080/os.v31.22031 Review of “European Breeding Bird Atlas 2: Distribution, Abundance and Change” (Keller V, Herrando S, Vorisek P et. al., eds, 2020) https://journals.lub.lu.se/os/article/view/22463 Jonas Waldenström Copyright (c) 2021 Jonas Waldenström http://creativecommons.org/licenses/by/4.0 2021-01-28 2021-01-28 31 19–21 19–21 10.34080/os.v31.22463 Review of “Ageing and Sexing of Migratory East Asian Passerines” (Norevik G, Hellström M, Liu D & Petersson B, 2020) https://journals.lub.lu.se/os/article/view/22489 Jonas Waldenström Copyright (c) 2021 Jonas Waldenström http://creativecommons.org/licenses/by/4.0 2021-02-09 2021-02-09 31 22–24 22–24 10.34080/os.v31.22489 Review of “Moult and Ageing of European Passerines, 2nd edition” (Jenni L & Winkler R, 2020) https://journals.lub.lu.se/os/article/view/22923 Jonas Waldenström Copyright (c) 2021 Jonas Waldenström http://creativecommons.org/licenses/by/4.0 2021-03-23 2021-03-23 31 30–33 30–33 10.34080/os.v31.22923 Breeding biology of the Red-throated Loon Gavia stellata on the Holmöarna archipelago, Northern Sweden https://journals.lub.lu.se/os/article/view/22276 <p>The aim&nbsp;of this study was to estimate number of breeding pairs, breeding success, and distance to fishing areas in a population of the Red-throated Loon <em>Gavia stellata</em> on two of the main islands in the Holmöarna Archipelago in the northern part of the Baltic Sea, Sweden. Potential breeding waters were surveyed during seven years, 2010–2015 and 2019. Red-throated Loons appeared in 43 of the 135 lakes of sufficient size on the islands, and the population was estimated to 25–35 pairs, or about 2% of the Swedish population. The mean size of lakes with breeding pairs was 1.6 ha, and these lakes had an average of 82% water surface without vegetation (18% vegetation cover). The mean breeding success was low, 0.30 chicks per pair and year, and at least during one year, chicks were produced in only 20 (47%) of the surveyed lakes. The average distance between the nesting waters and the fishing areas for 17 studied pairs was 1.8 km. We discuss the characteristics of suitable nesting waters as well as the factors contributing to the low reproduction.</p> Christer Olsson Jan Pettersson Frank Johansson Copyright (c) 2021 Christer Olsson, Jan Pettersson, Frank Johansson http://creativecommons.org/licenses/by/4.0 2021-05-31 2021-05-31 31 1–18 1–18 10.34080/os.v31.22276 Covariation between systematic counts and spontaneous reporting of staging waders at the Getterön Nature Reserve, southwestern Sweden https://journals.lub.lu.se/os/article/view/22270 <p>This paper is an attempt to describe how strong the covariation is between systematic counts and spontaneous reporting of staging waders at the Getterön Nature Reserve in southwestern Sweden. The material is based on systematic and spontaneous observations of twelve species of waders, made on the same days during the autumn migration in July–October 2010–2019. There is a significant positive correlation between the two methods for nine of twelve species. However, there is a large variation in the strength of the correlations, with the strongest correlation seen for Dunlin <em>Calidris alpina</em>. The Wood Sandpiper <em>Tringa glareola</em>, Green Sandpiper <em>Tringa ochropus</em>, and Little Stint <em>Calidris minuta</em>, on the other hand, show no significant correlations. This shows the difficulties in evaluating quantitative data of the wader occurrence at stopover areas such as Getterön. The variation in correlation between count methods between different species entails an uncertainty, which is probably due to low reliability in the spontaneous reporting. Thus, in the case of studies of staging waders based solely on spontaneous data, caution should be exercised.</p> Reino Andersson Copyright (c) 2021 Reino Andersson http://creativecommons.org/licenses/by/4.0 2021-04-05 2021-04-05 31 34–43 34–43 10.34080/os.v31.22270 Changes in numbers and distribution of wintering waterbirds around Gotland 1969–2020 https://journals.lub.lu.se/os/article/view/22254 <p>The coastal areas of the island of Gotland in the center of the Baltic Sea is an important wintering site for waterbirds in Sweden. Gotland offers extensive areas of shallow feeding grounds and, due to its location, some open waters remain available even during harsh winters. Wintering waterbirds have been counted annually on the island since the start of the International Waterbird Census in 1967, with full coverage of all the inshore areas around the main island obtained during the years 1969–1978 and 2013–2020. Between these two periods, the mean total number of wintering waterbirds increased from 32,000 to 111,500. The most numerous species were Mallard <em>Anas platyrhynchos</em>, Tufted Duck <em>Aythya fuligula, </em>and Common Goldeneye <em>Bucephala clangula</em>. Some species such as Eurasian Wigeon <em>Mareca penelope</em>, Eurasian Teal <em>Anas crecca</em>, and Gadwall <em>Mareca strepera </em>started to winter during the second period. Marked increases were also found for Smew <em>Mergellus albellus </em>and Greater Scaup <em>Aythya marila</em>, likely related to progressively milder winters in recent years.</p> Leif Nilsson Clas Hermansson Copyright (c) 2021 Leif Nilsson, Clas Hermansson http://creativecommons.org/licenses/by/4.0 2021-06-10 2021-06-10 31 78–93 78–93 10.34080/os.v31.22254 Plumage changes in an intersex Mallard Anas platyrhynchos over a six-year period https://journals.lub.lu.se/os/article/view/22427 <p>Intersex individuals with a mixture of female and male plumage traits are reported regularly, but at low frequency. Here we describe the changes in plumage in a Mallard <em>Anas platyrhynchos</em> intersex individual over six years (2015–2020), from a mixed female–male phenotype to a predominantly male phenotype. Already at the first observation, typical male characteristics were present, such as greyish-white tail with two central curved black rectrices and a greenish tinge to parts of the head. The bird attained a more male-like plumage with the next moult and maintained that plumage for the rest of the study period. However, presence of female-patterned body feathers continued until 2019, but in reduced frequency, except for the cheeks and ear-coverts, which displayed a variation in colour. The bill remained female-patterned throughout and the bird did not enter eclipse plumage.</p> Ann-Katrin Sjögren Jonas Waldenström Copyright (c) 2021 Jonas Waldenström, Ann-Katrin Sjögren http://creativecommons.org/licenses/by/4.0 2021-06-04 2021-06-04 31 68–74 68–74 10.34080/os.v31.22427 Clas Hermansson in memoriam https://journals.lub.lu.se/os/article/view/23214 Lotta Berg Åke Abrahamsson Copyright (c) 2021 Lotta Berg, Åke Abrahamsson http://creativecommons.org/licenses/by/4.0 2021-06-10 2021-06-10 31 75–77 75–77 10.34080/os.v31.23214 Bird predation by cats—an alternative way to estimate the number of birds killed https://journals.lub.lu.se/os/article/view/22534 <div> <p class="BrdtextA"><span class="Ingen">Many studies have tried to estimate the number of birds killed by cats, most of them based on the number of birds killed by a smaller number of cats in a local area and then scaled to larger areas, or a whole country. Such estimates can be confounded by several factors, and the results of one study may not always be applicable in another setting where climate, habitats, and societal structure differ. Here I used an alternative approach to estimate cat predation on birds using ring recoveries of birds reported to the Swedish national ringing scheme as killed by cats. With the assumption that ringed birds are taken by cats in an equal proportion as unringed birds, I estimate that about 0.03% of all passerine birds are killed by cats in Sweden annually. This amounts to about 100,000 birds per year, which is much lower than previous estimates. </span></p> </div> Hans Ryttman Copyright (c) 2021 Hans Ryttman http://creativecommons.org/licenses/by/4.0 2021-02-13 2021-02-13 31 25–29 25–29 10.34080/os.v31.22534