bluuebunny/crossref_metadata_2025 huggingface dataset:
Populationsstruktur hos övervintrande strömstare Cinclus c. cinclus i norra Lappland 2002—2005
Authors: Tyrén Håkan , Gustafsson Hans
Published: March 2023

During the winter seasons October—April 2002—2005, we caught Dippers in the Tjautjas river (67°22'N, 20°49'E), northern Lapland. The age and sex structure was monitored and the territory activities were observed. The number of females was significantly higher than the number of males, a result opposite to our assumption that males should be most common because they are dominant over females. The age distribution between juveniles and adults fluctuated strongly between the years and did not differ significantly from the one found among more than 3,600 wintering birds ringed all over Fenno-Scandia. The Dippers were more mobile than we expected. Unringed Dippers appeared in the stream during the whole winter season, and some individuals disappeared. They shifted spots frequently during winter and interactions were uncommon. Some Dippers also returned to the stream after a few weeks’ absence. Our interpretation is that the Dippers in the Tjautjas river do not defend territories in the strict sense but instead use overlapping homeranges that may involve also other rivers in the area.
A comparison between ringing totals at Falsterbo, SW Sweden, ringing totals at Ottenby, SE Sweden, and point counts from the Swedish Breeding Bird Census during 20 years (1980—1999)
Authors: Karlsson Lennart , Ehnbom Sophie , Walinder Göran
Published: March 2023

Autumn ringing totals from Falsterbo, SW Sweden, and Ottenby, SE Sweden, and data from the Breeding Bird Census were compared in 37 species during 1980—1999. We compared both 20-year trends (continuity of changes) and mean totals for the 1980s and 1990s, respectively. The three programmes showed similar patterns in many species. More species showed decreasing than increasing trends. There were no significant differences in the number of significant trends between the three programmes or between the numbers of significantly decreasing trends among long-distance and other categories of migrants. The two-decade comparison showed more negative changes among long-distance than among other migrants at Falsterbo, and long-distance migrants decreased most at Falsterbo and least in Point Counts. Possible reasons for the differences are (a) different populations, especially between Falsterbo and Ottenby, (b) trends in partial migrants may not be detected in ringing totals, (c) non-random route selection in Point Counts, (d) difficult to count very common species in Point Counts, and (e) decreases of more species in Western than in Eastern Europe, affecting Falsterbo.
Juvenile Black-legged Kittiwakes Rissa tridactyla with deformed bills and clubfeet in the Barents Sea
Authors: Kylin Henrik
Published: March 2023

Juvenile Black-legged Kittiwakes Rissa tridactyla with deformed bills and feet were observed in the Barents Sea in 1996, first while passing between Franz Josef Land and Novaya Zemlya on 21–24 July (at least 10 birds) and then off the West Coast of Svalbard 20–21 September (at least 2 birds). Deformities were manifest as prolonged upper or lower mandible, hooked or crocked upper mandible, crossed bill and clubfeet. This paper reports the circumstances of the observations and discusses possible causes. Among the possible causes are nutritional deficiencies, epizootic events, environmental pollutants (persistent organic pollutants, heavy metals or radioactivity), or combinations of these.
Effekter av oljeutsläpp på övervintrande alfågel Clangula hyemalis vid Hoburgs bank i centrala Östersjön mellan 1996/97 och 2003/04
Authors: Larsson Kjell , Tydén Lars
Published: March 2023

The Baltic Sea is an important marine area for wintering birds. Surveys in the 1990s showed that more than 25% of the European Long-tailed Duck Clangula hyemalis population wintered at Hoburgs bank and east of Gotland. A shipping route with very frequent traffic goes from southwest Baltic Sea via Öland, Hoburgs bank and east of Gotland to the Gulf of Finland. In year 2000 about 58,500 ships passed east of Öland along this route. Hundreds of oils spills are registered along the route each year. Weekly surveys of oiled birds at southern Gotland and analyses of birds that had drown in fish nets showed that tens of thousands of Long-tailed Ducks were injured by oil each year in central Baltic Sea. Of 998 birds that drowned in fish nets at Hoburgs bank 11.8% were found to have oil in the plumage. There was no clear relationship between the number of oiled birds observed and the number of registered oil spills in different years. Many sea duck have a life history in which variable or low productivity is compensated for by relatively high adult survival. This makes sea duck populations very susceptible to extra adult mortality caused by oil spills.
Seasonal changes in body size and mass of Red Knots Calidris canutus during autumn migration through southern Baltic
Authors: Meissner Włodzimierz , Kamont Piotr
Published: March 2023

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.
Boöverlevnad hos strandängshäckande vadare: den relativa betydelsen av predation och trampskador av betesdjur
Authors: Ottvall Richard
Published: March 2023

Nest survival among eight wader species Charadrii in relation to densities of grazing livestock (0–2 livestock/day/ha) was investigated on Öland, southeastern Sweden in 2004. When analysing a pooled data set of 173 nests, nest survival was not related to densities of livestock. Only six nests were destroyed from trampling by livestock and the estimated trampling risk of nests was low. Another analysis of 122 nests produced significantly negative relationships between nest survival and initiation of incubation. Nests were depredated more often later in the season. Nest survival was not related to livestock density or to vegetation height at nests. Mayfield estimates of hatching success were 2–21% for four of the different wader species. The highest hatching success was found in Lapwing Vanellus vanellus (21%) and Ringed Plover Charadrius hiaticula (20%), and the lowest in Oystercatcher Haematopus ostralegus (2%), while Redshank Tringa totanus had intermediate hatching success (11%). This study indicates that, at current grazing management, predation has a higher relative impact on nest survival of waders breeding on coastal meadows compared to direct and indirect effects of grazing animals.
Wintering swans Cygnus spp. and Coot Fulica atra in the Öresund, South Sweden, in relation to available food recources
Authors: Nilsson Leif
Published: March 2023

In connection with the building of a Fixed Link (bridge – artificial island – tunnel) between Sweden and Denmark intensive studies of waterfowl and benthic fauna and flora in the Öresund were undertaken as a part of the Environmental Impact Assessment Study. This paper analysis the occurrences of staging and wintering herbivores (i.e. Mute Swan Cygnus olor and Coot Fulica atra) in relation to available food resources. It was concluded that the proportion of Zostera and Ruppia consumed by the birds during September–March was about 10% of the available standing crop in the autumn or less. During ice-periods large parts of the available feeding areas are covered by ice, and during an extended ice-period in 1995/1996 the calculated food consumption for the ice-free areas was of the same magnitude as the calculated standing crop of food plants.
Revirstruktur och häckningsframgång hos ett unikt bestånd av skärpiplärka Anthus petrosus littoralis i hamnmiljö
Authors: Andersson Reino
Published: March 2023

A unique Rock Pipit Anthus petrosus littoralis population was established in an industrial environment in the harbour of Varberg in the late 1980s. It rose to 17 territories in 1994, then declined to extinction in 2004. In a detailed study (1993—1996), 57 territories were found (41 breeding pairs, 8 non-breeding pairs, and 8 unpaired males). Most nests lay on the ground but several up to 5.5 m above ground. 52 clutches were found: 38 first clutches, 19 failed; 9 replacement clutches, 6 failed; 5 true second clutches, 4 failed. 65% of the failures were caused by predators. Fledging success was 1.6 young per breeding attempt and 2.2 per breeding pair. 61% of males, 40% of females, but only 1% of fledglings returned to the study area in the following spring, adults always to the same territory. The establishment of this unique harbour population may be explained by habitat deterioration (higher vegetation, bushes), possibly enhanced by increasing predation, in adjacent natural coastal habitats. Later, harbour development and pavement of former weedy feeding grounds, and the high depredation of nests, explains the decline and extinction of the harbour population.
Preferenser för olika fälttyper hos häckande jordbruksfåglar – en litteraturstudie
Authors: Berg Åke , Kvarnbäck Olle
Published: March 2023

This study compiles results from studies of preferences for different arable field types for 31 farmland birds. Most species avoided autumn sown cereals and preferred set-asides, especially rotational set-asides. The preference patterns were more complex for spring-sown cereals and cultivated grasslands. Cultivated grasslands were preferred by omnivores and insectivores and avoided by herbivores and herbivores/insectivores. A similar, but weaker, pattern was found for spring-sown cereals. Food preferences seemed to be more strongly associated to field type preferences than to other ecological characters. However, these are not independent of each other; for instance, eight of 10 insectivores are ground nesters and nine insectivores have small or intermediate territories. For most species, set-asides restricted to edge zones and field borders would be beneficial. However, for open field species (e.g. Skylark), large fields with set asides are needed. It is probable that certain threshold levels in areas of set-asides are needed before effects on a national or regional level could be seen. Furthermore, a time lag of several years should be expected before effects of increased areas of set-aside could influence population sizes.
Smålommens Gavia stellata häckningsframgång i relation till vattenkemi och fiskbeståndens sammansättning i olika fiskevatten
Authors: Eriksson Mats O G
Published: March 2023

Breeding performance by Red-throated Diver Gavia stellata was compared to water chemistry, light penetration and density of fish in 34 freshwater lakes used for foraging in South and Central Sweden. The study covered around 25% of the breeding population in these parts of the country. Fishing lakes were overall nutrient-poor, and some of them were also acidic and had a poor buffering capacity. There were no relationships between breeding success and water chemistry (pH, alkalinity, total phosphorus), light penetration or impact of acidification. Species composition of the fish communities was characteristic for nutrient-poor lakes: on average 6.6 fish species per lake and dominance of Perca fluviatilis, Rutilus rutilus, Esox lucius and Coregonus albula. The survival of chicks was correlated to high abundance of cyprinid and salmonid fish, i.e. the dominant prey delivered to non-fledged chicks. Around 300 freshwater lakes are judged to be of importance as foraging sites for breeding Red-throated Divers in Sweden. Continuous and long-term liming is a prerequisite in order to maintain viable fish stocks in those lakes that are acid or have a poor buffering capacity.
Ankomstdatum 1948—2006 och häckning 1978—2006 i Jämtland för svartvit flugsnappare Ficedula hypoleuca, rödstjärt Phoenicurus phoenicurus och lövsångare Phylloscopus trochilus
Authors: Sjöberg Nils
Published: March 2023

First arrival date of Pied Flycatcher Ficedula hypoleuca, Redstart Phoenicurus phoenicurus, and Willow Warbler Phylloscopus trochilus did not change in the province of Jämtland, Sweden (c. 63° N) during the period 1948—2006. This accords with absence of any change of April or May temperature during the same period. Breeding success was high except when the nestling period was rainy and cool (more than 3 days with rain and maximum temperature below 10° C caused severe nestling mortality). Number of Pied Flycatchers declined but high breeding success seems to exclude local factors as the cause. During the 1990s it was more difficult to get new nest-boxes occupied than it was in the 1970s (observations in other groups than those used in this study), indicating that it was the number of spring arrivals that had declined, in turn indicating that the decline may have been caused by mortality during migration or in the winter quarters.
Fuelling in front of the Sahara desert in autumn—an overview of Swedish field studies of migratory birds in the eastern Mediterranean
Authors: Fransson Thord , Jakobsson Sven , Kullberg Cecilia , Mellroth Roger , Pettersson Thomas
Published: March 2023

Birds must store fuel prior to the crossing of the Sahara desert, at least 1,500 km with few refuelling possibilities. A major question is how inexperienced birds know where to prepare for the oncoming barrier. Experiments with caged birds showed that information from the Earth’s magnetic field close to the desert might trigger extensive fuel deposition. Blackcaps Sylvia atricapilla trapped on Cyprus in September and October were much heavier than in Sweden during the early phase of autumn migration, typical for birds preparing for crossing the Sahara desert. There is a potential cost of being fat. Fat Sedge Warblers Acrocephalus schoenobaenus on Lesvos had much poorer take off abilities than lean birds, making them more vulnerable to predators. Swallows Hirundo rustica trapped at a roost site on Rhodes showed a synchronized body mass increase and this is in agreement with their wavelike pattern of passage on Crete. In recent years, studies of fuelling behaviour and stopover duration of first-year Garden Warblers Sylvia borin have been started on Crete with the aid of radio-transmitters.
Distribution and population changes of two subspecies of Chiffchaff Phylloscopus collybita in Sweden
Authors: Lindström Åke , Svensson Sören , Green Martin , Ottvall Richard
Published: March 2023

We describe the breeding distribution and population trends of the two subspecies of Chiffchaff Phylloscopus collybita that occur in Sweden. Our data come from the Swedish Bird Survey: free choice point counts (1975—2006) and fixed (and habitat-representative) line transects (1996—2006). Ph. c. abietinus occurs north of about 60°N with a stronghold in central Sweden and along the coast of the Bothnian Bay. This population declined with about 75% between 1983 and 1997, but has increased again during the last decade, matching closely the changes in Finland. Ph. c. collybita, a recent immigrant, breeds mainly in southwesternmost Sweden. The population in 2006 was estimated to be 15 times larger than in 1975 but with little range expansion. The breeding distribution of the two subspecies does not yet overlap. The distribution of the northern subspecies seems to be determined by the occurrence of spruce forest, and the northern range border may be set by early autumn frost. The recent positive trend in the north may possibly be due to an increase in area of old spruce forest.
Puffin harvesting and survival at Nólsoy, The Faeroes
Authors: Stempniewicz Lech , Jensen Jens-Kjeld
Published: March 2023

At least 10,000 Puffins Fratercula arctica are taken annually at the Nólsoy colony by fowling. This figure probably exceeds the recruitment rate and may cause gradual decrease of the colony size. Continuous decline (since 1900) of the number of breeding birds as well as shrinking of the colony area suggest long-lasting overexploitation. The collapse of the local population is probably delayed only by immigration of immature Puffins from the large Icelandic population. We recovered 37 (20.1%) of 184 Puffin fledglings ringed in 1997 at Nólsoy colony. All rings originated from birds caught by fowlers operating on Nólsoy (34 birds) and on other Faeroe islands (3 birds). First Puffins were fowled at colony in 1999, 54% in 2000 (3 yrs old), and the last bird in 2003 as 6 yrs old. Puffins which had been harvested, i.e. those which survived at least 2 years, were on average larger and heavier at fledging than the rest of the ringed chicks. Most of them originated from early broods. Our data suggest that adult Puffins breeding earlier produce better quality offspring that survive in higher proportion.
Häckningsbiologiska rön från en långtidsstudie över en skandinavisk population av talgoxe Parus major
Authors: Borgström Erik
Published: March 2023

In the surroundings of the small community of Råda, Sweden (60°00'N, 13°36'E) approximately 350 nest boxes were checked annually during 20 years (1985–2004) with more or less daily visits during the breeding season. Data for 950 original clutches, 125 replacement clutches and 77 second clutches of Great Tit producing at least one fledgling were recorded. The mean date of laying the first egg was 10 May without any trend in spite of increasing trend of spring temperature. However, annual date of laying was correlated with April spring temperature (at least one degree warmer than average advanced laying with at least two days). The mean size of all first clutches was 8.74 eggs, which is less than shown by other long-term studies from the Nordic area. The number of eggs laid by young females was the same as for other females, a result that differs from other studies. In the studied area the ratio of second clutches in relation to the number of original clutches was 0–16.7% (average 8%), which is far less than normally reported.
Green Warbler Phylloscopus (trochiloides) nitidus recorded at Ottenby, Öland: a first record for Scandinavia
Authors: Irwin Darren E , Hellström Magnus
Published: March 2023

This paper presents the circumstances surrounding the findings and identification of the first Green Warbler Phylloscopus (trochiloides) nitidus for Sweden. The bird was caught and ringed at Ottenby Bird Observatory on May 29, 2003, but was not formally identified to subspecific level until after a DNA analysis of the collected blood-sample was conducted. This constitutes the sixth European record outside the restricted breeding area.
Current status and population dynamics of nominate subspecies of Lesser Black-backed Gull Larus fuscus fuscus in the White Sea
Authors: Cherenkov Alexander , Semashko Vladimir , Tertitski Grigori
Published: March 2023

The size of the colonies of the nominate subspecies of Lesser Black-backed Gull Larus fuscus fuscus was monitored annually in Onega Bay of the White Sea in 1989—2006. The total current population in the studied area is about 2,100 pairs or 10% of the world population of this subspecies. During the time of monitoring the population increased more than three times, and since the 1960s it has increased more than six times. The main increase was observed in the seven biggest colonies (more than 100 pairs) where more than 60% of the White Sea population was breeding. Average long-term clutch size was 2.44, and breeding success was 1.0 fledgelings per pair. The increase in number probably results from the decrease of disturbance in the breeding area and improvement of feeding resources. The increase of the White Sea population contrasts with a strong decline of the Baltic population.
First, second and replacement broods in the breeding biology of a Treecreeper Certhia familiaris population
Authors: Enemar Anders
Published: March 2023

The breeding behaviour of a Treecreeper population that bred in nest pockets and in which all females were colour-ringed was followed over ten seasons. On average, 50% of the first breeding attempts in spring failed. Between half and two thirds of the successful females were double-brooded. The remaining females were single- brooded. These two breeding categories were identical in terms of initial clutch size and egg volume. The double-brooded females invested less in their second than their first clutch. Most of the females that failed laid replacement clutches of similar size as in the first attempt but with larger eggs. A replacement brood where young successfully fledged was never followed by a second breeding attempt. The average distance between the first and the repeat nest was the same for double-brooded and replacement-breeding females. The egg volumes of the first and the repeat clutches were strongly correlated. The double-brooded pairs were the most common breeding category and reared 50% of the population’s total output of fledged broods, while the single-brooded and replacement breeding pairs each fledged ca. 25%. The adaptive values of the three breeding categories are compared.
Revirtäthet och boplatsval av skata Pica pica i olika typer av urbana miljöer
Authors: Viktor Tomas
Published: March 2023

The breeding population of Magpie Pica pica was censused in a 200 hectare surburban area (Vårberg) in the south-west part of Stockholm in 2007. The area was divided into four different zones to evaluate the effect of different types of urban settings. A total of 113 nests were found, and density differed significantly between zones. The density of breeding Magpies was 9 pairs/km2 in a zone with no buildings (“natural” habitats). In a zone with detached and terraced houses the density was 53 pairs/km2. In a zone with apartment buildings less than four stores high the density was 81 pairs/km2. This was the highest density, close to tenfold the density found in the zone without buildings. In a zone with tall buildings exceeding three stores, the density was 66 pairs/km2. The nests were generally placed higher up in the trees in the zone with natural habitats than in the zones with buildings. Nests were found in 16 different species of trees with pine and whitebeam being the most frequent ones, but no single favourite could be detected.
Occurrence of Continental Blackcaps Sylvia atricapilla in northern Europe
Authors: Bengtsson Daniel , Fransson Thord , Røer Jan Erik
Published: March 2023

A recent increase of wintering Blackcaps in Scandinavia is suspected to derive from migration from central Europe. We used ringing recoveries to determine their origin. Because Blackcaps breeding in Scandinavia have longer wings than more southern Blackcaps, we also analysed wing length data from seven Nordic bird observatories to see whether there was an influx of short-winged, probably continental Blackcaps. The results showed that Scandinavia is now a part of the Blackcap’s regular wintering range. As many as 17% of Blackcaps ringed in Sweden and found again during the same autumn were recovered north of an E–W axis. This is an outstandingly high figure compared to 0–7% in some other species. A strong significant difference in dates of ringing was discovered between “long-winged” (>73 mm) and “short-winged” (<74 mm) Blackcaps. An influx of short-winged Blackcaps started in late September and this was more pronounced in Norway than in Sweden and Finland. It is probably these birds, not Scandinavian breeders forestalling migration, that are observed at bird tables during the winter.
Sjöfågelbeståndets utveckling i Bullerö skärgård efter invandring av mink
Authors: Andersson Åke
Published: March 2023

Population sizes were followed in some waterbird species breeding in the outer part of the Stockholm archipelago in the brackish Baltic Sea. Pair numbers were censused during four years by counts of nests or adult birds attached to potential breeding sites. The Mink Mustela vison appeared in the inner part in 1972 and reached the outer island groups ten years later. During the period there were relatively large population changes, the Eider Somateria mollissima, the Greylag Goose Anser anser and the Great Black-backed Gull Larus marinus increased markedly in numbers while the Lesser Black-backed Gull Larus fuscus, the Razorbill Alca torda and the Black Guillemot Cepphus grylle decreased dramatically. The increases as well as the decrease of the Lesser Black-backed Gull were consistent with general trends in the Baltic. The temporal and spatial pattern of the decrease of the Razorbill and the Black Guillemot, both specialised hole-nesters, strongly support the conclusion that the predation of the Mink is the main reason. For the marked distribution shift within the study area noted for the Eider and the Herring Gull Larus argentatus, Mink predation is also suspected.
Status and population changes of farmland birds in southern Sweden
Authors: Robertson Jeremy , Berg Åke
Published: March 2023

Since 1950 there have been considerable changes in the use of Swedish farmland which have led to a more large-scale, homogeneous and intensively managed agricultural landscape. These changes in Swedish farmland have affected the populations of many farmland birds. We give the densities of 29 selected farmland birds and 15 selected species of forest birds at eight large study sites (farmland landscapes of 14.5–21.5 km2 size; total of 140 km2) in southern Sweden and review the population changes of 48 species of farmland birds in southern Sweden. The number of breeding farmland bird species at the different sites was positively correlated with total farmland area, area of scrub and trivial deciduous forest, as well as with the fragmentation of the forest landscape; there were more farmland species in fine-grained than in coarse-grained landscapes. Species found in forest edges and dry pastures were the most widespread ones (found at most sites), and included several species with high densities. Most of these species have not decreased as dramatically as other species. Several species of arable land were also widespread, but most of them have declined in numbers since 1950, possibly as a consequence of changes in farming practices. Meadow is the farmland habitat that has declined most, and this is reflected in the low densities and scattered distribution of many species found on cut or grazed meadows. Several of these species are now largely confined to marginal habitats and areas where farmland still has a traditional structure. However, on abandoned meadows overgrown with bushes and trees a few successful colonists are increasing in numbers. Of the 48 farmland birds breeding in Sweden the populations of only 10 have remained relatively stable since 1950; seventeen have increased (8 markedly) while 21 have decreased (12 markedly). Of the 21 species that primarily breed on farmland, 9 (43%) have declined markedly compared with only 3 (11%) of the 27 secondary farmland birds, which have a large proportion of the population in other habitats. Similarly, only 5% of the primary species have increased markedly compared with 26% of the secondary species. More primary than secondary farmland species are also extinct, or categorized as endangered, vulnerable or requiring consideration on Swedish Red Data lists. Large parts of the Swedish farmland are now being taken out of production, which probably will have negative effects on several farmland bird populations.
The primary moult of the Brambling Fringilla montifringilla evaluated by four different methods
Authors: Holmberg Thomas
Published: March 2023

The primary moult of the Brambling Fringilla montifringilla was studied between 1988 and 1991 at Ånnsjön (63°15'N; 12°28'E) in the Swedish mountain region. The duration of primary moult was estimated in four different ways: 1) By linear regression of population data; 2) By calculating the mean duration of moult of 34 recaptured birds, assuming a linear relationship between time and moult progression; 3) By using data from the same recaptured birds but correcting for the non-linear progression of moult; 4) By using field data on the rate of shedding of different primaries and the growth rate of individual feathers to construct a moult score versus time curve. Linear regression of population data gave results varying from 32 to 70 days depending on population and method of analysis. The other three methods all resulted in a primary moult duration of 58–60 days. The recaptured birds often showed a weight decrease between captures but this seemed not to affect the moult speed. The mean starting date of moult of the population varied from 8 July to 18 July in the four years. The males tended to start a little earlier than the females, but the difference is not significant. The estimated duration of primary moult (ca 59 days) is considerably longer than the result (46.5 days) of another recently published study. The difference is probably due to different methods of analysis.
Blodparasiter och deras spridningsvägaar inom fågelfaunan
Authors: Borg Karl
Published: March 2023

The occurrence of blood parasites (Leucocytozoon, Haemoproteus, Plasmodium, Trypanosoma, and microfilaria) was determined in 774 birds of 50 different species, collected in 1948—1960. The incidence varied considerably, being high in e.g. gallinaceous birds and zero in waders. Usually, birds carrying parasites showed no signs of being detrimentally affected. Only a few fatal infections are reported: Leucocytozoon in Tetrao uragallus and Anas platyrhynchos, Plasmodium in T. uragallus and Pica pica, and Haemoproteus in Strix aluco. The sample includes a special study of 299 waders of 12 species on autumn migration. None of them carried any blood parasites. There is little that suggests that long distance transport of blood parasites should be important for the level of infection among birds in Sweden. High incidence in several resident species rather shows that the parasites are well established in the country, and the short incubation time for at least some parasites in relation to the period of spring migration supports the same view.
The age of young Willow Warblers Phylloscopus trochilus estimated from different stages of post-juvenile moult
Authors: Bensch Staffan , Lindström Åke
Published: March 2023

A scale for estimating the progression of post-juvenile moult in Willow Warblers is described. The scale was used on birds caught at Ammarnäs, Swedish Lapland in 1984—1991 . Two data sets were used to determine the average age (days since hatching) of birds in different stages of moult. First, 91 Willow Warblers with known hatching date were later retrapped and examined for state of moult. Most of these birds were caught in the earlier stages of moult. Second, birds first caught in one stage of moult were retrapped in later stages and this enabled an estimate to be made of the average age of juvenile Willow Warblers in the later stages of moult. The moult of juveniles commences at an age of 26 days, just after the outermost primaries reach full length. Few birds with completed moult were registered but data suggest that moult ends around 60 days of age. The scale is also applicable to juveniles of many other passerine species, but there are exceptions.
The occipital face of the Pygmy Owl Glaucidium passerinum
Authors: Vesnen Mikael
Published: March 2023

Through fluffing of the headfeathers the patterning on the nape of the Pygmy Owl can be transformed into a face-like structure known as an occipital face. Concealed patterns, unknown until now and corresponding to real Pygmy Owl eyes, lie dormant until a forward headtilt occurs; the eye pattern itself being produced by the synthesis of patterned parts on at least two feathers, converging into an “eye” only when intentionally exposed. Occipital face patterns of similar general type occur in several Glaucidium species, three of which were examined by the author (Glaucidium gnoma, G. perlatum and G. brasilianum). Surprisingly, no positive evidence of “hidden-eye” patterns was found in these latter species.
Male and female Penduline Tit Remiz pendulinus can reverse their desertion decisions
Authors: Czyż Beata , Persson Olof , Öhrström Peter
Published: March 2023

The Penduline Tit Remiz pendulinus is a species that displays uniparental care. Either the female or the male parent abandons the clutch before incubation commences, and both parents desert about 30% of clutches. Deserting individuals may nest again and have up to six partners over a breeding season. We describe five cases of an apparent reversal of the decision to desert by four male and one female Penduline Tit in Sweden and Poland. Several days after abandoning a clutch, the individuals returned to their nests and began incubation. All clutches were successful.
Rovfåglar i Kvismaredalen vintrarna 1954/55—1989/90
Authors: Larsson Leif
Published: March 2023

The purpose of this study is to analyze whether any changes have occurred in the number of birds of prey wintering in Kvismaredalen in the middle of Sweden during the period 1954/55—1989/90. The results show that Golden Eagle Aquila chrysaetos, Rough-legged Buzzard Buteo lagopus, Sparrowhawk Accipiter nisus and Goshawk Accipiter gentilis were the most common species in the beginning of the monitoring period. At the end of the period Golden Eagle, White-tailed Eagle Haliaetus albicilla, Sparrowhawk and Goshawk together with Merlin Falco columbarius were the most numerous species. The study also shows that especially White-tailed Eagle and Merlin have increased their winter occurrence. The increase in White-tailed Eagles has taken place in the latter half of the 1980's whereas the Merlin has been relatively numerous during the whole of the 1970's and 1980's. Golden Eagle, and to a lesser extent also Sparrowhawk and Goshawk, have shown increases but these took place in the 1960's. Two species specializing in rodents, Rough-legged Buzzard and Short-eared Owl Asio flammeus, have both shown strong decreases. Buzzards Buteo buteo are also showing a decrease after a temporary increase during the 1960's. The fact that Kestrels Falco tinnunculus have not wintered since 1980/81 indicates a decrease for that species.
Age dependent variation in wing length of Bearded Tits Panurus biarmicus
Authors: Nielsen Bo
Published: March 2023

I have studied the increase of wing length among Bearded Tits from their juvenile plumage to their autumn plumage. The increase is large, 8.5% for males and 7.3% for females. During 1992 I obtained data on several other feather measurements of these two plumages in order to find the ecological background of the increase in wing length. From juvenile plumage to autumn plumage tail length increased with 14–16%. There were also an increase in feather mass. The average mass of the innermost primary was 3.32 mg in juveniles and 4.10 mg in their autumn plumage. Indices of wing pointedness and aspect ratio show that adults grow a more pointed wing than juveniles. Different hypotheses to explain the age related increase in wing length are discussed. I argue that the shorter wings in juveniles is an evolutionary adaptation. The reason should be to bring down the time until fledging in order to reduce the risk of predation. I could find no data in favour of the alternative hypothesis, that starvation of nestlings reduces the growth rate of feathers. Moreover there might also be different wing length optima for juvenile and adult birds.
Variation in survival in an increasing population of the Greylag Goose Anser anser in Scania, southern Sweden
Authors: Nilsson Leif , Persson Hakon
Published: March 2023

Based on resightings of neck-banded Greylag Geese, we calculated mean annual survival rates of 76% for juveniles, 74% for subadults and 83% for adults. The survival rate was significantly lower over the winters 1989/90 and 1990/91 than over the winters 1985/86—1988/89 and 1991/92 for adults (80 vs 87%). In the winters 1989/90 and 1990/91, hunting on Greylag Geese was intensive in southwestern Spain. Greylags wintering in the Netherlands (mainly the Dutch Delta) had significantly higher survival rates than birds wintering in southwestern Spain in both juveniles (90 vs 72%) and adults (94 vs 85%). Most losses occurred during autumn migration and just after arrival into the winter quarters.
Regional song dialects of the Ortolan Bunting Emberiza hortulana L. in Sweden
Authors: Åström Gustav , Stolt Bengt-Olov
Published: March 2023

During the period 1966—1990 we studied the occurrence of different song dialects of the Ortolan Bunting in Sweden. Song dialects were identified for more than 420 males from about 150 different localities. We found that two regional dialects, one Northern Swedish and one Central Swedish, were prevailing. The characteristics of these two dialects are shown on melograms with one curve for fundamental frequency and one curve for relative sound pressure. The dialects can be identified and the differences clearly heard in the field without technical means. The Northern Swedish dialect is predominant north of the province of Hälsingland and the Central Swedish dialect south of that province. The two dialects meet and “overlap” in Hälsingland. The picture is supplemented by the occurrence of individuals with the foreign dialect, both dialects or a mixed dialect.
Seabird distribution and numbers in selected offshore parts of the Baltic Sea, winter 1992
Authors: Durinck Jan , Skov Henrik , Andell Per
Published: March 2023

In the period from 27 January to 10 March, 1992, a seabird line-transect study was carried out in the Baltic Sea. The study focused on selected shallow waters and included previously largely unsurveyed areas of the former Soviet Block. The results of this study give a lot of new information on the distributions and numbers of several waterfowl species. Black- and Red-throated Divers Gavia arctica/stellata totalled 26,000 of which at least 18,500 were Red-throated Divers. Three areas (the Gulf of Pommern, the Gulf of Riga and the Irbe Strait) each housed more than 10% of the estimated populations of Black- and Red-throated Divers in NW Europe. Long-tailed Ducks Clangula hyemalis totalled 2,500,000 with ca 1 mill. in the Gulf of Pommern, 682,000 in and around the Gulf of Riga and 532,000 in the area off eastern Gotland, Hoburgs Bank and the Midsjo Banks. Velvet Scoters Melanitta fusca totalled 450,000 with 286,000 in the Gulf of Pommern and 137,000 in the Gulf of Riga. Red-necked Grebes Podiceps grisegena totalled ca 1,800, Slavonian Grebes Podiceps auritus ca 2,000 and Black Guillemots Cepphus grylle 26,000.
Duvhökens Accipiter gentilis överlevnad och skattning av dess populationsutveckling i Sverige
Authors: Ryttman Hans
Published: March 2023

In this study I have used recovery data from 691 Goshawks Accipiter gentilis that were ringed as nestlings between 1971 and 1990. The survival of the Goshawk was 34.4% in the first year, 61.6% in the second year, and 73.5% thereafter. Only 20% of the Goshawks reached an age of 2 years and 2 months, i.e. the age when they make their first breeding attempt. I used data on survival and reproductive success to estimate if the Swedish Goshawks had a stable population size. Provided that all breeding attempts are successful, the population is rather stable (x = +0.8%, 95% confidence limits: -7.6% +9.2%). With a more reasonable estimate of successful breeding attempts (30% of first time breeders, 60% of second time breeders and 100% of thereafter) the population is decreasing with on average 9%. A comparison of mark-recapture data from Swedish Pheasant farms suggests, however, that the Swedish Goshawk population has been rather stable during the 1980s.
Biotopval, populationsutveckling och häckningsbiologi hos skärpiplärka Anthus spinoletta littoralis i ett småländskt skärgårdsområde
Authors: Larsson Tommy
Published: March 2023

A population of breeding Rock Pipit Anthus spinoletta littoralis was studied in 1979—1990 in the archipelago off Oskarshamn in southeastern Sweden. Between 9 and 31 pairs were found breeding in the study area, at densities of 0.04–0.13 pairs/hectare in the different years. Population density declined abruptly between 1984 and 1985, probably due to harsh winter conditions. Territory size was usually 1–3 hectares. Average clutch size was 5.29 eggs/ clutch and 4.53 chicks/clutch. For their breeding Rock Pipits preferred habitats with stones, seaweed on the shoreline and a rich cover of low vegetation, to more barren habitats. Breeding success was higher in the preferred habitat.
Dynamics of a passerine bird community in a small deciduous wood, S Sweden, during 40 years
Authors: Enemar Anders , Cavallin Berith , Nyholm Erik , Rudebeck Inga , Thorner Ann Mari
Published: March 2023

The passerine bird community of a 13 ha nature reserve, consisting of a narrow valley with deciduous woods and open areas, was censused yearly from 1953 through 1992 by territory mapping. Its size, showing no significant trend, was on average 124± 15(SO) territories, belonging to 20±2 species. The community has fluctuated significantly (range 103 to 158, CV=12%). Its stability was founded on the restricted fluctuations of the most abundant species. Out of the 39 stationary species, 19 (=95% of the community size) appeared there for more than 20 years, only 8 of which have been yearly present. Fringilla coelebs, Phylloscopus trachilus, Sylvia borin, and Luscinia luscinia were the most abundant species throughout. Emberiza hortulana, Carduelis cannabina, and Anthus trivialis disappeared, while Sturnus vulgaris, Sitta eurapaea, Carduelis chloris, and Turdus pilaris immigrated. The species turnover rate between successive years was 21.7±9.7%, the long-term rate being about 1%. The community structure changed gradually: taken together, the population sizes of residents and short-distance migrants increased, from 38 to 57% of the community size; the tropical migrants declined correspondingly. These two species groups showed an opposing and significant covariation.
The distribution of breeding Merlins Falco columbarius in relation to food and nest sites
Authors: Wiklund Christer G , Larsson Bengt L
Published: March 2023

This study deals with nest site selection and with the importance of food and nest sites as determinants of breeding density of Merlins Falco columbarius. Merlins preferred Hooded Crow Corvus corone comix nests less than 2 years old, which had not been used previously by Merlins. Artificial nests meeting these requirements were provided in a study area where the number of suitable nests for Merlins was low. Food abundance (number of passerines) was estimated in this area and in a control area where up to 15 Merlin pairs could breed. The number of breeding Merlin pairs did not increase in the nest provision area in relation to the number of nests provided. One possible reason was that the accessibility of prey was limited by snow, which was much more abundant in the nest provision area than in the control area. Therefore, we suggest that the density of breeding Merlins in this area was mainly determined by food particularly during the mating period.
Flycatching behaviour in some passerines during the late breeding season at Ammarnäs, Swedish Lapland
Authors: Cuadrado Mariano
Published: March 2023

Many passerines have been recorded flycatching in the late breeding season in northern Swedish forests. In this paper, I analyze how flight energy costs according to Minimum Energy Power (sensu Pennycuick 1989) correlated with flycatching behaviour. Species included are (with increasing rank of flight energy cost): Spotted Flycatcher Muscicapa striata, Whinchat Saxicola rubetra, Yellow Wagtail Motacilla flava, Reed Bunting Emberiza schoeniclus, Brambling Fringilla montifringilla, and White Wagtail Motacilla alba. On average, birds performed 0.6–2.3 flights/30s and captured from 0 up to 10 prey per flight. Number of prey captured per flight varied significantly among species (from 0.8 to 1.1 prey). The efficiency of capturing prey (percentage of successful single capture flights) also varied between species, from 72% in the Whinchat to 97% in the White Wagtail. The percentage of multi-capture flights did not, however, vary. In two species, the multi-capture flights significantly reduced the time spent flying per prey. Flight energy costs were positively correlated with flycatching rate and number of prey captured per flight. The extensive use of flycatching is interpreted as an opportunistic response to local super-abundance of highly rewarding prey, mostly insects Isoperla grammatica, O. Plecoptera, during a period of presumed high energetic demands by birds.
The Red-backed Shrike Lanius collurio in southeastern Sweden: Breeding biology
Authors: Olsson Viking
Published: March 2023

The breeding biology of Red-backed Shrikes was studied in Gryt, southeastern Sweden from 1956–94. The shrikes used many different kinds of nest sites and a variety of nest materials. Parallel to an increased colonization of planted clear-cuts, young spruce has become more often used as a nest site. Mean clutch size was 5.3 eggs when also late clutches and repeat layings were included. The mean size of clutches in May was 5.64, with a marked decrease during the course of the summer. Average breeding success was 3.4 fledged young, with failing nests included, while it was 4.3 for successful nests (i.e. nests from which at least one young fledged). Nests suffering total loss made up 19.8% of 11 nests; total loss was mostly the result of predation. There were great differences in breeding success between favourable and unfavourable springs. Juvenile Red-backed Shrikes stayed near the nest up to one month after fledging after which they left, often still together and attended by the adults. Breeding success was good in the study area over the whole study period, and, contrary to the situation in other parts of Sweden, the local population showed no signs of a decline. Such a decline has been very marked (75% or more) in the northern part of the breeding area. Periods of bad weather there seem to hit the population harder than further south. Probably the poor reproduction reported for the Swedish population of Red-backed Shrikes refers to these marginal areas of the breeding range. It is possible that the shrikes are negatively affected by factors acting during the major part of the year when they live outside the Swedish breeding area.