White-spotted Bluethroat Luscinia svecica cyanecula is the latest addition to the Swedish bird fauna, with the first breeding in Scania in 2015. There were only three records on the Swedish West Coast north of Scania through 2016 and the first breeding was reported in 2018. Censuses performed in 2020 and 2021 revealed 12 and 17 singing males, respectively. Out of 39 singing males 2017–2021, 36 were found in Halland. Most birds were found in coastal wetlands with reedbeds, to which they arrived mainly in April. Nine males represented breeding pairs and second clutches were later observed for four breeding pairs. The Swedish expansion should be seen in the context of Danish immigration in combination with a large-scale advance via the Netherlands and Germany. The White-spotted Bluethroat belongs to those range-expanding taxa that are expected to increase due to warmer climate. As there is plenty of appropriate habitats, not least rapeseed fields, the conditions favour a continued range expansion in southern Sweden.
{"title":"Invandringsförloppet hos vitstjärnig blåhake Luscinia svecica cyanecula på svenska västkusten","authors":"Reino Andersson","doi":"10.34080/os.v32.23429","DOIUrl":"https://doi.org/10.34080/os.v32.23429","url":null,"abstract":"White-spotted Bluethroat Luscinia svecica cyanecula\u0000is the latest addition to the Swedish bird fauna, with the first breeding in Scania in 2015. There were only three records on the Swedish West Coast north of Scania through 2016 and the first breeding was reported in 2018. Censuses performed in 2020 and 2021 revealed 12 and 17 singing males, respectively. Out of 39 singing males 2017–2021, 36 were found in Halland. Most birds were found in coastal wetlands with reedbeds, to which they arrived mainly in April. Nine males represented breeding pairs and second clutches were later observed for four breeding pairs. The Swedish expansion should be seen in the context of Danish immigration in combination with a large-scale advance via the Netherlands and Germany. The White-spotted Bluethroat belongs to those range-expanding taxa that are expected to increase due to warmer climate. As there is plenty of appropriate habitats, not least rapeseed fields, the conditions favour a continued range expansion in southern Sweden.","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47160554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Birds are fascinating. For one thing, they can do what we cannot, like flying—as easily as anything at that, like a flock of Common Swifts Apus apus hastening through the late summer skies with their piercing screams, or a Wandering Albatross Diomedea exulans whose tip of the wing slices the ocean surface while the bird rides the wave troughs. For another, their appearance, their song, and their behaviours are so incredibly variable. In short, if you have ever really seen a bird, you will be forever smitten.
{"title":"On the wing","authors":"J. Waldenström, Martin Stervander","doi":"10.34080/os.v32.23825","DOIUrl":"https://doi.org/10.34080/os.v32.23825","url":null,"abstract":"Birds are fascinating. For one thing, they can do what we cannot, like flying—as easily as anything at that, like a flock of Common Swifts Apus apus hastening through the late summer skies with their piercing screams, or a Wandering Albatross Diomedea exulans whose tip of the wing slices the ocean surface while the bird rides the wave troughs. For another, their appearance, their song, and their behaviours are so incredibly variable. In short, if you have ever really seen a bird, you will be forever smitten.","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47193826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Increased understanding of the need to save endangered and locally extinct species has led to restoration or preservation of populations through reintroductions. Reintroduction of a species is worthwhile if the prerequisites for existence at the historical location have improved. Thus, background information about the habitat requirements of a target species is important for introduction programmes to be successful. The Black Stork Ciconia nigra was lost as a breeding species in Sweden during the 20th century, but recent observations and reports of potential breeding indicate that habitat conditions for Black Stork in Sweden may have improved. In this study, we used species characteristics and references to identify habitats in Sweden suitable for potential reintroduction of Black Stork. We identified several suitable areas in the former distribution range of this species in southern Sweden. Seven Swedish counties contained more than 18 % suitable habitat within their total area, with highest proportions in Jönköping County (25.8 %), Blekinge County (23.9 %), Västra Götaland County (22.1 %) and Kronoberg County (20.7 %). We suggest these areas to be made the primary targets for Black Stork reintroduction in Sweden.
{"title":"Black Stork Back: Species distribution model predictions of potential habitats for Black Stork Ciconia nigra in Sweden","authors":"C. Thulin, Malin Sörhammar, J. Bohlin","doi":"10.34080/os.v32.22081","DOIUrl":"https://doi.org/10.34080/os.v32.22081","url":null,"abstract":"Increased understanding of the need to save endangered and locally extinct species has led to restoration or preservation of populations through reintroductions. Reintroduction of a species is worthwhile if the prerequisites for existence at the historical location have improved. Thus, background information about the habitat requirements of a target species is important for introduction programmes to be successful. The Black Stork Ciconia nigra was lost as a breeding species in Sweden during the 20th century, but recent observations and reports of potential breeding indicate that habitat conditions for Black Stork in Sweden may have improved. In this study, we used species characteristics and references to identify habitats in Sweden suitable for potential reintroduction of Black Stork. We identified several suitable areas in the former distribution range of this species in southern Sweden. Seven Swedish counties contained more than 18 % suitable habitat within their total area, with highest proportions in Jönköping County (25.8 %), Blekinge County (23.9 %), Västra Götaland County (22.1 %) and Kronoberg County (20.7 %). We suggest these areas to be made the primary targets for Black Stork reintroduction in Sweden.","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45312884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pablo Jiménez-Nájar, Jorge Garrido-Bautista, R. Tarifa, J. Rivas, G. Moreno-Rueda
The diets of the Barn Owl Tyto alba and the Short-eared Owl Asio flammeus have been extensively studied worldwide over the past few years, especially on the Iberian Peninsula. Nevertheless, very few studies have examined the diets and the trophic niche overlap in areas where these two raptor species occur in sympatry. As such, in this study we compared the diets of the Barn Owl and the Short-eared Owl inhabiting agricultural landscapes of the Vega de Granada, south-east Spain, based on pellet analysis. The diets were very similar, as both owls preyed mainly on small mammals, the Algerian Mouse Mus spretus being the prey most commonly found in pellets from both species. Although the diet of the Barn Owl was more diverse than that of the Short-eared Owl, the food niche overlap was very high, thus indicating a low interspecific trophic segregation. Despite the similarities between both diets, the frequency of the Mediterranean Pine Vole Microtus duodecimcostatus was much higher in pellets from the Barn Owl, thus suggesting that the Barn Owl may exert pest control in years when the Mediterranean Pine Vole occurs in high numbers.
{"title":"Diet of sympatric Barn Owls Tyto alba and Short-eared Owls Asio flammeus in an agricultural landscape in south-east Spain","authors":"Pablo Jiménez-Nájar, Jorge Garrido-Bautista, R. Tarifa, J. Rivas, G. Moreno-Rueda","doi":"10.34080/os.v31.23108","DOIUrl":"https://doi.org/10.34080/os.v31.23108","url":null,"abstract":"The diets of the Barn Owl Tyto alba and the Short-eared Owl Asio flammeus have been extensively studied worldwide over the past few years, especially on the Iberian Peninsula. Nevertheless, very few studies have examined the diets and the trophic niche overlap in areas where these two raptor species occur in sympatry. As such, in this study we compared the diets of the Barn Owl and the Short-eared Owl inhabiting agricultural landscapes of the Vega de Granada, south-east Spain, based on pellet analysis. The diets were very similar, as both owls preyed mainly on small mammals, the Algerian Mouse Mus spretus being the prey most commonly found in pellets from both species. Although the diet of the Barn Owl was more diverse than that of the Short-eared Owl, the food niche overlap was very high, thus indicating a low interspecific trophic segregation. Despite the similarities between both diets, the frequency of the Mediterranean Pine Vole Microtus duodecimcostatus was much higher in pellets from the Barn Owl, thus suggesting that the Barn Owl may exert pest control in years when the Mediterranean Pine Vole occurs in high numbers.","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44778518","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Niklas Liljebäck, K. Koffijberg, Christine Kowallik, J. Månsson, Å. Andersson
Following the use of Barnacle Geese Branta leucopsis as foster parents in a conservation program for the endangered Lesser White-fronted Goose Anser erythropus in Sweden 1981–1999, mixed breeding pairs of the two species were established in the wild. We find indications that this was related to shared moulting habits of the two species in the Bothnian Sea during late 1990s. Starting in 2003, five mixed pairs produced at least 49 free-flying hybrid offspring until 2013, when the last breeding was confirmed. Reported numbers of hybrids did not increase in parallel to the production of young hybrids over time. After 2013, the number of hybrids started to decrease in Sweden and the Netherlands. Lower numbers of hybrids than expected can partly be explained by management actions taken, but may also be associated with low survival due to genetic outbreeding. Mixed pairs and their offspring entirely adopted the migratory habits of Barnacle Geese, overlapping very little with sites used by Lesser White-fronted Geese. We find no evidence that the hybrids ever posed a serious threat to Lesser White-fronted Geese breeding in Fennoscandia.
{"title":"Use of foster parents in species conservation may cause conflicting objectives: hybridization between Lesser White-fronted Goose Anser erythropus and Barnacle Goose Branta leucopsis","authors":"Niklas Liljebäck, K. Koffijberg, Christine Kowallik, J. Månsson, Å. Andersson","doi":"10.34080/os.v31.22430","DOIUrl":"https://doi.org/10.34080/os.v31.22430","url":null,"abstract":"Following the use\u0000 \u0000 of Barnacle Geese Branta leucopsis as foster parents in a conservation program for the endangered Lesser White-fronted Goose Anser erythropus in Sweden 1981–1999, mixed breeding pairs of the two species were established in the wild. We find indications that this was related to shared moulting habits of the two species in the Bothnian Sea during late 1990s. Starting in 2003, five mixed pairs produced at least 49 free-flying hybrid offspring until 2013, when the last breeding was confirmed. Reported numbers of hybrids did not increase in parallel to the production of young hybrids over time. After 2013, the number of hybrids started to decrease in Sweden and the Netherlands. Lower numbers of hybrids than expected can partly be explained by management actions taken, but may also be associated with low survival due to genetic outbreeding. Mixed pairs and their offspring entirely adopted the migratory habits of Barnacle Geese, overlapping very little with sites used by Lesser White-fronted Geese. We find no evidence that the hybrids ever posed a serious threat to Lesser White-fronted Geese breeding in Fennoscandia. ","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44351284","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Recension av ”Fugleatlas: de danske ynglefugles udbredelse 2014–2017” (Vikstrøm T & Moshøj CM, redaktörer, 2020)","authors":"Jonas Waldenström","doi":"10.34080/os.v31.23538","DOIUrl":"https://doi.org/10.34080/os.v31.23538","url":null,"abstract":"","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42408608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gough Moorhens Gallinula comeri were introduced to Tristan da Cunha in the 1950s, and are now numerous in lowland habitat, filling the ecological niche of the extinct Tristan Moorhen G. nesiotis. On their native Gough Island, moorhens have a varied diet, ranging from vegetation and fruits to scavenging and even predatory behaviour. Here, we examined the stomach contents of four birds on Tristan da Cunha to provide insight into their diet. Moorhens mostly ate vegetation, but we also recorded spiders (Arthropoda: Aranea), earthworms (Oligochaeta: Lumbricidae), remains of introduced rodents (Mus musculus), and anthropogenic debris. As on Gough Island, moorhens on Tristan have a generalist diet, and the impact of ecosystem restoration (and of the moorhens themselves) should be considered.
{"title":"Diet of the introduced Gough Moorhen Gallinula comeri on Tristan da Cunha","authors":"A. Bond, G. McClelland","doi":"10.34080/os.v31.23476","DOIUrl":"https://doi.org/10.34080/os.v31.23476","url":null,"abstract":"Gough Moorhens Gallinula comeri were introduced to Tristan da Cunha in the 1950s, and are now numerous in lowland habitat, filling the ecological niche of the extinct Tristan Moorhen G. nesiotis. On their native Gough Island, moorhens have a varied diet, ranging from vegetation and fruits to scavenging and even predatory behaviour. Here, we examined the stomach contents of four birds on Tristan da Cunha to provide insight into their diet. Moorhens mostly ate vegetation, but we also recorded spiders (Arthropoda: Aranea), earthworms (Oligochaeta: Lumbricidae), remains of introduced rodents (Mus musculus), and anthropogenic debris. As on Gough Island, moorhens on Tristan have a generalist diet, and the impact of ecosystem restoration (and of the moorhens themselves) should be considered.","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42798671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Species-specific tracks animals can be an effective way of mapping species that are hard to find even if they are present. We used observations of sap rows on trees to calculate densities of Eurasian Three-toed Woodpeckers Picoides tridactylus. We surveyed 14 fixed routes in northern Sweden below the montane forest for sap rows during the autumn of 2020. We used our observations of fresh sap rows together with average home range and proportion of active territories per year derived from the literature, to calculate large-scale woodpecker population density. The density based on sap rows was 0.19 pairs per km2. Densities from fixed route bird observations for different parts of Västerbotten County below the montane forests were 0.13–0.14 pairs per km2, in relative agreement with the estimates from sap rows. We also calculated the population density from fixed route observations in the montane forests, and these were almost three times higher. Our density calculations correspond to 7,900 pairs in Västerbotten County. These results indicate that systematic counts of sap rows can quickly provide credible population density estimates of Eurasian Three-toed Woodpeckers.
{"title":"Densities of the Eurasian Threetoed Woodpecker Picoides tridactylus calculated from sap row surveys are on par with estimates from fixed route bird censusing","authors":"Björn Ferry, J. Ekenstedt, Martin Green","doi":"10.34080/os.v31.22416","DOIUrl":"https://doi.org/10.34080/os.v31.22416","url":null,"abstract":"Species-specific tracks animals can be an effective way of mapping species that are hard to find even if they are present. We used observations of sap rows on trees to calculate densities of Eurasian Three-toed Woodpeckers Picoides tridactylus. We surveyed 14 fixed routes in northern Sweden below the montane forest for sap rows during the autumn of 2020. We used our observations of fresh sap rows together with average home range and proportion of active territories per year derived from the literature, to calculate large-scale woodpecker population density. The density based on sap rows was 0.19 pairs per km2. Densities from fixed route bird observations for different parts of Västerbotten County below the montane forests were 0.13–0.14 pairs per km2, in relative agreement with the estimates from sap rows. We also calculated the population density from fixed route observations in the montane forests, and these were almost three times higher. Our density calculations correspond to 7,900 pairs in Västerbotten County. These results indicate that systematic counts of sap rows can quickly provide credible population density estimates of Eurasian Three-toed Woodpeckers.","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43962718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Body size and mass of 1,458 juvenile and 558 adult Knots were measured during autumn migration in Puck Bay, Poland, between 1983 and 1999. The measurements fit well with those gathered along the migration route of Siberian Knots Calidris c. canutus. All linear measurements of adults, except body mass adjusted for size, were significantly higher than those of juveniles. Shorter wing in juveniles than in adults seems to be a general rule regardless of geographical region. Adult females migrated ahead of males, confirmed by decreasing mean measurements. Juveniles carried larger relative energy stores than adults. Puck Bay may be an emergency feeding place for adult Knots, whereas juveniles may use it as one of many stop-over sites. Juveniles were significantly smaller, but had higher adjusted body mass, in late September than earlier, indicating a behavioural difference between late and early birds during preceding stages of migration. Late juveniles probably follow a time-minimising strategy with larger fuel stores and fewer stop-over sites, whereas birds passing in August migrate with very small energetic reserves, making only short flights and stops.
在1983年至1999年期间，我们在波兰的Puck Bay测量了1458只幼鱼和558只成鱼在秋季迁徙期间的体型和质量。这些测量结果与西伯利亚结Calidris c. canutus迁徙路线上收集的数据吻合得很好。除体型调整后的体重外，成虫的所有线性测量值均显著高于幼虫。无论地理区域如何，幼鱼的翅膀比成年鱼短似乎是一个普遍规律。成年女性在男性之前迁移，这一点通过减少平均测量值得到证实。幼鱼携带的相对能量比成年鱼多。帕克湾可能是成年结鸟的紧急觅食地点，而幼鸟可能会把它作为许多中途停留的地点之一。9月下旬的幼鸟明显比之前的小，但调整后的体重更高，这表明晚鸟和早鸟在迁徙前阶段的行为差异。晚生的幼鸟可能会采取时间最小化的策略，储存更多的燃料，减少中途停留的地点，而8月份经过的候鸟的能量储备非常少，只进行短途飞行和停留。
{"title":"Seasonal changes in body size and mass of Red Knots Calidris canutus during autumn migration through southern Baltic","authors":"W. Meissner, Piotr Kamont","doi":"10.34080/os.v15.22744","DOIUrl":"https://doi.org/10.34080/os.v15.22744","url":null,"abstract":"Body size and mass of 1,458 juvenile and 558 adult Knots were measured during autumn migration in Puck Bay, Poland, between 1983 and 1999. The measurements fit well with those gathered along the migration route of Siberian Knots Calidris c. canutus. All linear measurements of adults, except body mass adjusted for size, were significantly higher than those of juveniles. Shorter wing in juveniles than in adults seems to be a general rule regardless of geographical region. Adult females migrated ahead of males, confirmed by decreasing mean measurements. Juveniles carried larger relative energy stores than adults. Puck Bay may be an emergency feeding place for adult Knots, whereas juveniles may use it as one of many stop-over sites. Juveniles were significantly smaller, but had higher adjusted body mass, in late September than earlier, indicating a behavioural difference between late and early birds during preceding stages of migration. Late juveniles probably follow a time-minimising strategy with larger fuel stores and fewer stop-over sites, whereas birds passing in August migrate with very small energetic reserves, making only short flights and stops.","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47331119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The stopover behaviour of Black-throated Divers Gavia arctica and Red-throated Divers Gavia stellata during autumn migration was observed in two sites in Poland. Differences in time-activity budget and diving pattern were recorded from mid-October to mid-January of 2004 and 2005. A total of 1,516 minutes of observation was achieved. Birds spent their time diving (60.7%), followed by preening (14.8%), surface swimming (12.5%), and other activities (12%). The feeding pattern of Red-throated Divers and Black-throated Divers was similar. Immature birds had significantly longer dives than adults and they made longer dive-pause intervals. This is suggested to be caused by the differences between age classes in detecting and capturing prey. Moreover, our results show that, in autumn, first-year divers spent less time foraging than adult birds, instead spending more time resting and surface swimming.
{"title":"Behaviour of Black-throated Diver Gavia arctica and Red-throated Diver Gavia stellata during autumn migration stopover","authors":"M. Polak, M. Ciach","doi":"10.34080/os.v17.22691","DOIUrl":"https://doi.org/10.34080/os.v17.22691","url":null,"abstract":"The stopover behaviour of Black-throated Divers Gavia arctica and Red-throated Divers Gavia stellata during autumn migration was observed in two sites in Poland. Differences in time-activity budget and diving pattern were recorded from mid-October to mid-January of 2004 and 2005. A total of 1,516 minutes of observation was achieved. Birds spent their time diving (60.7%), followed by preening (14.8%), surface swimming (12.5%), and other activities (12%). The feeding pattern of Red-throated Divers and Black-throated Divers was similar. Immature birds had significantly longer dives than adults and they made longer dive-pause intervals. This is suggested to be caused by the differences between age classes in detecting and capturing prey. Moreover, our results show that, in autumn, first-year divers spent less time foraging than adult birds, instead spending more time resting and surface swimming.","PeriodicalId":52418,"journal":{"name":"Ornis Svecica","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2021-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42142191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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