bluuebunny/crossref_metadata_2025 huggingface dataset:
Female-biased sex ratios and the proportion of cryptic male morphs of migrant juvenile Ruffs (Philomachus pugnax) in Finland
Authors: Jaatinen K. , Lehikoinen A. , Lank D. B.
Published: December 2023

Biases in sex ratio may affect the viability of populations, and may arise for different rea-sons, such as biased primary ratio and differential juvenile or adult mortality of sexes. Global populations of Ruffs are thought to be strongly female biased. To determine the demographic origin of this sex bias, we report the sex ratios among juvenile Ruffs on their southward migration in Finland during 1985–2006. We also quantify the proportion of cryptic, female-like 'faeder'males at this demographic stage, and examine migration tim-ing by sex. We found a strong female bias in juvenile populations; across the study years, 34% of individuals were males. Female juveniles migrated earlier than male juveniles. Faeder males made up ca. 1% of juvenile populations, similar to estimates from mixed-age populations elsewhere. These results, combined with previous studies, confirm the strong female bias and the low frequency of 'faeders'at the juvenile stage of the Ruff. The sex bias might thus demographically originate from sex-allocation strategies by females at the egg stage. Given the genetic determination of the status of faeders, their proportion among juveniles provides the first estimate of the morphs' proportional reproductive suc-cess.
Nestling diet of the Common Magpie (Pica pica) in urban and agricultural habitats
Authors: Kryštokofvá M. , Fousová P. , Exnerová A.
Published: December 2023

Several processes may be responsible for the urbanization of the Common Magpie (Pica pica), a species spreading widely in European towns during the last 50 years. Greater supply or better availability of food could play a role in the successful colonization of urban habitats by this species. We compared the nestling diet of Magpies within (urban) and adjacent to the city (rural) of Prague, Czech Republic, using the neck-collar method, and studied parental foraging behavior and micro-habitat associations in the city of Prague. Although the nestling diet was different between urban and rural areas, invertebrates (mainly Coleoptera) were the most frequent prey in both areas. Anthropogenic food was more abundant in urban than in rural areas. The nestling diet differed from the potentially available food supply in both urban and rural areas: Annelida and Lepidoptera were preferred, while Isopoda, Diplopoda, Orthoptera and Hymenoptera were neglected. In urban areas, Magpies foraged actively (i.e., by walking) and by perching. Prey was collected mostly from the ground. Magpies foraged mainly at sites covered with short vegetation. Utilization of short vegetation was proportional to its availability, whereas tall vegetation was used less than could be expected by availability. Short vegetation dominated the home ranges of Magpies in urban areas, while tall vegetation was more common in the Magpie home ranges in rural areas.
Does Reed Bunting (Emberiza schoeniclus) predict the risk of nest predation when choosing a breeding territory? An experimental study
Authors: Trnka A. , Peterková V. , Grujbárová Z.
Published: December 2023

Increasing evidence suggests that birds minimize the risk of nest predation by preferentially settling in territories with low predator encounter rate. However, little is known about whether they are also able to assess the actual risk of nest predation at the time of habitat occupancy and choose their breeding territories accordingly. Here, we tested this prediction experimentally, using artificial nests placed in 29 Reed Bunting territories and 29 in randomly-selected non-territories located in the same habitat. Simultaneously, we estimated the spatial distribution of the main Reed Bunting nest predator in the study area, viz. the Marsh Harrier. Nests located in Reed Bunting territories were predated less frequently (14%) than were nests placed in non-territories (41%), and this was also associated with the relative abundance of Marsh Harriers in territories (average 3.7) and in non-territories (average 5.8). These findings support the hypothesis that Reed Buntings may be capable of choosing their territories according to the actual predation risk.
The role of residential habitat type on the temporal variation of wintering bird assemblages in northern Finland
Authors: Jokimäki Jukka , Kaisanlahti-Jokimäki Marja-Liisa
Published: December 2023

Wintertime ecological studies conducted in different kinds of residential areas over sev-eral winters have thus far been lacking. The objective of this study was to analyze if the between-winter variability of bird communities differs between urban residential habitat types. The study was conducted in five blocks of flats areas, five single-family house ar-eas, and five villages in Rovaniemi, northern Finland, during five winters. Birds were sur-veyed using a single-visit study plot (30 ha) method. The average between-winter varia-tion (CV%) in bird species richness was 27% and in bird abundance was 53%, and these values did not differ between the three types of residential areas. Temporal variation of species in residential areas was species-specific. The lowest between-winter variation was observed for omnivore or feeding table species such as the Great tit Parus major (50%), Magpie Pica pica (53%) and House Sparrow Passer domesticus (76%). The high-est variation was observed for berry-eating species, such as the Bullfinch Pyrrhula pyrrhula (196%) and Waxwing Bombycilla garrulus (192%). The between-winter vari-ation (CV%) of abundance of most species was greater in the blocks of flats areas than in the other residential-area types. The between-winter average qualitative similarity was 76.1% in the blocks of flats areas, 80.0% in the single-family house areas, and 78.0% in the villages, and these values did not differ between types of residential areas or between study winters. Stability of winter communities decreased from the centre to the periphery of Rovaniemi. We suggest that the stabilizing, warmer microclimate near the urban core of the town partly explains this result. The average species turnover rate (%) in the block of flats areas was 22.8, in single-family house areas was 20.5, and in the villages was 21.6. In general, the lowest between-winter similarities, highest species turnover rates, and the highest between-winter variation of abundance of individual species were observed in ar-eas of blocks of flats. Our results suggest that single-family house and village areas are better overwintering areas for wintering birds than areas of blocks-of-flats. Intensive win-ter feeding might stabilize the between-winter variation of bird assemblages especially in single-family house areas. In addition, the warmer microclimate near the urban core might probably also stabilizes variation in residential bird assemblages.
Declines amongst breeding Eider Somateria mollissima numbers in the Baltic/Wadden Sea flyway
Authors: Ekroos Johan , Garthe Stefan , Meissner Wlodzimierz , Nilsson Leif , De Boer Peter , Cervencl Anja , Laursen Karsten , Green Martin , Jonsson Jon E. , Kilpi Mikael , Petersen Ib K. , Christensen Thomas K. , Fox Anthony D. , Öst Markus
Published: December 2023

We report on the status of the Baltic/Wadden Sea flyway Eider population based on trends in breeding and wintering numbers throughout the region, supplemented by changes in the sex ratio and proportion of young Eiders as monitored in the Danish hunting bag. At the flyway scale, total numbers of breeding pairs decreased by 48% during 2000–2009, after relatively stable breeding numbers in 1991–2000. The majority of the population nest in Finland and Sweden, where the number of breeding pairs has halved over the same period. After initial declines in winter numbers between 1991 and 2000, during 2000– 2009, national wintering numbers increased in the Baltic Sea, but decreased in the Wadden Sea. The annual proportion of adult females in the Danish hunting bag data de-Ornis Fennica 89:81–90. 2012 creased from ca. 45% (1982) to ca. 25% (2009) and simultaneously the proportion of first-winter birds fell from ca. 70% to ca. 30%, indicating dramatic structural changes in the Danish wintering numbers. These results suggest that the total flyway population will ex-perience further declines, unless productivity increases and the factors responsible for de-creasing adult female survival are identified and ameliorated. We discuss potential popu-lation drivers and present some recommendations for improved flyway-level monitoring and management of Eiders.
Low flea loads in birds' nests in tree cavities
Authors: Hebda Grzegorz , Wesolowski Tomasz
Published: December 2023

High flea (Siphonaptera) loads are typically found in birds’ nests in nestboxes. Ten years of observations, involving Marsh Tit Poecile palustris, Great Tit Parus major and Blue Tit Cyanistes caeruleus nests in tree cavities in primeval forests of Białowieża National Park, Eastern Poland, demonstrated that the prevalence of fleas was below 10% of nests and that the intensity of flea infestation was low. Low flea loads may constitute a typical feature for nests in tree cavities. Therefore, nest-box data on flea-host interactions should not be treated as representative for conditions in natural holes.
Pre-breeding foraging and nest site habitat selection by Lesser Spotted Woodpeckers Dendrocopos minor in mature woodland blocks in England
Authors: Charman Elisabeth C. , Smith Ken W. , Dodd Steve , Gruar Derek J. , Dillon Ian A.
Published: December 2023

Lesser Spotted Woodpeckers Dendrocopos minor have dramatically declined and retracted in range in Britain. Pre-breeding foraging may be critical and, although work has been carried out elsewhere in Europe our knowledge of habitat requirements for British birds is limited.We aim to describe foraging behaviour and selection of foraging locations in the pre-breeding period; and to provide descriptions of nest sites and wider habitat selection for nesting.We recorded foraging behaviour, attributes of foraging trees and nest site characteristics and compared them with random areas within woods. Small branches of live oaks at heights usually in the upper third of the tree were most frequently used for foraging. At a wider scale, areas selected contained more deadwood. Nest cavities were usually placed in the upper half of a tree, and oak was commonly used. For nesting, open areas were selected with more dead trees and a mature structure. Many of the attributes important for foraging and nesting have changed in English woodlands in the direction expected to have negative impacts on this species, except for deadwood. Further work shouldmeasure food availability in areas of differing structures. Knowledge of declining species' resource requirements allows targeted and informed management for conservation.
Moult migration of Latvian Whooper Swans Cygnus cygnus
Authors: Boiko Dmitrijs , Kampe-Persson Hakon
Published: December 2023

This study is the first to demonstrate moult migration in the Whooper Swan Cygnus cygnus. Of cygnets hatched in Latvia and known to be alive about 99% left the country to moult somewhere else in their 2nd-6th calendar year. One-sixth of these were re-sighted in Finland during moult migration; these were solely from western Latvia. Moulting sites were recorded for nine individuals, of which seven had been marked with neck collars and two had satellite transmitters. Five of these nine swans moulted in Latvia, one in Estonia and three in the Arkhangelsk Region of Russia. Distances between sites of ringing and moulting varied between 0 and 1,455 km. All individuals were recorded moulting as two-or three-year old birds. Those moulting in Russia left Latvia/Estonia before 20 June and returned after mid September.
Territorial calls in the Little Owl (Athene noctua): spatial dispersion and social interplay of mates and neighbours
Authors: Jacobsen Lars B. , Sunde Peter , Rahbek Carsten , Dablesteen Torben , Thorup Kasper
Published: December 2023

With the aim of quantifying spatio-temporal and social factors affecting territorial calls in Little Owls, we collected data on the calling behaviour of radio tracked individuals from a low-density population in Northern Jutland, Denmark. There was considerable seasonal variation in calling activity. During the breeding season, males calling away from the nest were located in the direction of the neighbouring nesting site, and males with a neighbour within hearing distance called more often than those with a longer distance to the nearest neighbour. Call posts were on average closer to the nest than telemetry observations, but did not appear to be related to mate distance. With a sound pressure level of 82 dB(A) at 1-m distance, the territorial calls were estimated to be audible to a distance of 4.4 km. Call posts were on average 4.1 m above the ground, which probably maximizes the transmission distance.
Organization, variation in time, and impacting factors in the song strophe repertoire in the Great Reed Warbler (Acrocephalus arundinaceus)
Authors: Leniowski Konrad , Wegrzyn Ewa
Published: December 2023

The song of the Great Reed Warbler (GRW) is produced by males before and during the breeding season in territory defense and mate attraction. To date, researchers studying the song of the species have mainly focused on syllable repertoire and its function. In this paper we present first data on the organization of strophes and their possible function in the GRW. We analyzed short- and long-term changes in strophe repertoire size and composition and the relationship between strophe repertoire and male age, philopatry and harem size. Syllables were organized in quite a large but still limited number of strophe types and variants, which were repeated by an individual male in the same or a relatively similar form within a season. Longitudinal analyses revealed significant effects of season and male age on strophe repertoire size. We also found a positive correlation between male harem size and strophe repertoire size. The composition of GRW strophe repertoire was stable within a season but significantly changed between years. At 3-year time intervals, GRW males exchanged more than half of their song types and almost all song variants. The level of between-year changes in song repertoire suggests that the GRW is a species adapted for learning.
Geographic variation in body mass of first-year Reed Warblers Acrocephalus scirpaceus in Iberia
Authors: Andueza Miren , Valkenburg Thijs , Tenreiro Paulo , Onrubia Alejandro , Neto Júlio M. , Moreno-Opo Rubén , Monrós Juan S. , Lozano Luis , Jubete Fernando , Gómez Jaime , Feliu Jordi , Arroyo Jose L. , Barba Emilio , Arizaga Juan
Published: December 2023

On their route to tropical Africa, European trans-Saharan migrants must cross two major geographical barriers, the Mediterranean Sea and the Sahara Desert, which necessitates the accumulation of large fuel loads.While northernAfrica is the chief region wheremost migrants gain fuel for the Sahara crossing, Iberia is a target area to gain fuel before the sea crossing existing between Europe andAfrica. Despite the large body of studies approaching the question of fuel accumulation before geographic barriers, it is still poorly known which factors apart from distance to a certain barrier shape the geographical pattern of fuel reserves. To investigate this question in detail we used data of first-year Reed Warblers from 12 localitieswithin Iberia during the autumnmigration period of 2009.We run linearmodels to analyze the effects of location in Iberia, date, and body size on bodymass variation at each migratory flyway (eastern, central and western Iberia). Flight ranges from each site were also calculated. Our results showed that ReedWarblers in Iberia had the necessary fuel needed to arrive in northernAfrica but not to tropical Africa. However, bodymass patterns varied depending on the geographical region (eastern, central or western Iberia).Date did not affect bodymass in central andwestern Iberia, but in eastern Iberia heavier birds tended to pass later. Thus, the factors shaping body mass of ReedWarblers in Iberia before the sea crossing to Africa seemed to be more complex than just the distance to this geographical barrier, with underlying stopover quality-associated factors possibly playing a relevant role.
Inter-annual and inter-habitat variation in breeding performance of Blue Tits (Cyanistes caeruleus) in central Poland
Authors: Gladalski Michal , Banbura Miroslawa , Kalinski Adam , Markowski Marcin , Skwarska Joanna , Wawrzyniak Jaroslaw , Zielinski Piotr , Cyzewska Iwona , Banbura Jerzy
Published: December 2023

Studies at various locations in Europe show that nest-box populations of tits in urban areas lay earlier and produce fewer eggs than do birds in rural areas. Long-term data on laying date and clutch size were studied for Blue Tit (Cyanistes caeruleus) populations in two, structurally and floristically contrasting sites (an urban parkland and a rich decidu-ous forest, located only 10 km apart) in central Poland. The peak abundance of caterpillars, the optimal food of breeding tits, was also studied at both breeding areas. We focused on four environmental factors; year, site, insect availability and ambient temperature. Birds initiated breeding earlier in the urban area compared to the forest area and the laying date was highly correlated with air temperature during the period between 15 March and 15 April. At both study areas there was a similar negative temporal trend – birds started breeding earlier with later years. The number of eggs laid per breeding pair tended to be lower in the parkland than in the forest and it is likely that this is due to the habitat-specific pattern of food abundance and patchy environment in the parkland. This study provides new data on the reproductive biology of a model species and also fills up some knowledge gaps concerning inter-habitat and macro-geographic patterns.
Unusual migratory behaviour in a newly established subpopulation of Whooper Swan (Cygnus cygnus) breeding in the highlands of Poland
Authors: Dudzik Krzysztof , Wlodarczyk Radoslaw , Czyz Stanislaw , Polakowski Michal
Published: December 2023

The migratory behaviour of a subpopulation of Whooper Swans breeding in highlands of southern Poland was studied over a 17-year period, from 1997 to 2013. Birds ringed in their breeding area spent winters and moulting periods in the vicinity of their natal sites, and the mean distance between breeding area and wintering sites was only 149.1 ± 11.7 km. Moreover, 57.0% of all winter re-sightings were obtained within 100 km of the study area. There was an increase in winter site fidelity by individual Whooper Swans over their lifetime (R 2 = 0.09, p = 0.019), reflected by a linear decrease in the distance travelled between two consecutive winters (b = 0.22 ± 0.09). We did not find any association between winter severity and the birds migratory behaviour, neither in the distance travelled nor the location of winter recoveries. The mean distance between the study area and the moulting site was 142.7 ± 34.6 km and c. 66.6% of ring re-sightings during the moulting period were within 100 km of the study area. During autumn many immature birds were observed close to their parents breeding territory and this could help them reunite with parents or siblings from other seasons. The apparent reduction of migratory behaviour compared with representatives of northern populations indicates behavioural plasticity in the Whooper Swan, which may facilitate further southward expansions of the species.
Variation in egg-size traits of the European Roller (Coracias garrulus) in eastern Poland
Authors: Górski Andrzej , Nowakowski Jacek J. , Banbura Jerzy
Published: December 2023

Life-history theory predicts that allocation of resources into offspring size and number should be traded-off. The trade-off may be masked in good environmental conditions and be expressed only in some reproductive attempts, when conditions are poor. In this paper we analyse variation in size-related traits of eggs in relation to clutch size in a marginal population of the European Roller (Coracias garrulus) in eastern Poland, declining as a result of agriculture intensification and habitat loss. Because large-bodied insects that constitute the main kind of food of Rollers are greatly affected by the weather in spring, we assumed that their abundance may differ from year to year in association with differences in weather conditions. We predicted that egg size-clutch size relationship and egg traits should differ between years in correspondence with environmental conditions prior to the time of egg laying. We also predicted that variation in egg size and shape should have some fitness-related consequences. We found that year and clutch size interacted in their influence on egg size: in one year egg size was positively and in another year negatively related to clutch size. We also found that egg shape (sphericity) was positively associated with clutch size and negatively related with the date of laying. Both egg size and spheric-ity in shape positively affected hatching success, thus confirming the existence of fitness-consequences of variation in the traits of Roller eggs. Our results are in general consistent with theoretical expectations, but we failed to find any specific links between egg size variation and the decline of the study population.
The impact of weather and the phase of the rodent cycle on breeding populations of waterbirds in Finnish Lapland
Authors: Lehikoinen Aleksi , Santaharju Jarkko , Pihlajaniemi Mari , Niemimaa Jukka , Mäkeläinen Sanna , Leppänen Jenni , Lehtomäki Joona , Lehikoinen Petteri , Laakkonen Hanna , Henttonen Heikki , Eriksson Heikki , Burgas Daniel , Fraixedas Sara , Välimäki Kaisa
Published: December 2023

Climate change may affect bird populations both directly by changing theweather conditions, and indirectly through changes in the food chain.While both theoretical and empirical studies have shown climate change having drastic impacts on polar areas, its consequences on Arctic bird species are still poorly known. Here we investigated how weather and changes in predator–prey interactions affected the annual growth rates of sub-Arctic birds bymonitoring the breeding numbers of three duck and sevenwader species in the alpine tundra of Finnish Lapland during 2005–2015 (except for 2006). We hypothesized that growth rates ofwaterbirdswould be positively associated with warm and dry weather due to improved reproductive success. Furthermore, we tested the hypothesis that waterbirds have a higher reproductive success during the cyclic rodent peaks, when predators mainly prey on rodents, than during the decline and low phases of the cycle, when predation pressure towards waterbirds increases. Results showed that population growth rates of breeding ducks were negatively associated with the sumof rainfall in the previous year. In waders, growth rates were positively associated with the phase of the rodent cycle in the same year. Our results emphasize the importance of monitoring Arctic bird populations on their breeding areas to explorewhat the consequences of climate changemight be for breeding waterbirds by linking the effects of both weather and rodent abundance.
Drivers of decline and changed nest-site preference of the Baltic eider: an island-level analysis from south-western Finland
Authors: Kurvinen Lasse , Kilpi Mikael , Nordström Mikael , Öst Markus
Published: December 2023

The recent large-scale decline of Eiders (Somateria mollissima) in the Baltic Sea is well documented by long-term population monitoring. One hypothesis to explain the decline is increased predation pressure during breeding, but because the decline has been steep and geographically broad, multiple drivers may be involved. Here we explore whether some of these hitherto unidentified drivers relate to the breeding habitat. To this end, we performed an analysis of long-termmonitoring data from ca. 300 islands from the Archipelago Sea, SW Finland, representing five geographical sub-areas, during 1993–2012. We analysed population trends and whether nest-site preference changed over time. The results showed steep population declines in the sub-areas farthest from themainland and a more moderate decline in the sub-area closest to the mainland. The presence of breeding gulls (Larus spp.) on the Eider breeding island had a consistently positive effect on Eider breeding numbers throughout the study period. In contrast, the presence of breeding White-tailed Sea Eagles (Haliaeetus albicilla) had a negative effect on breeding numbers, but only during the early study period when the Eagle breeding populationwas still small. Interestingly, the sign of the effect of the distance from the nearest neighbouring island on Eider breeding numbers changed over time. Eider breeding numbers positively correlated with island size and distance to neighbouring islands in the early period, whereas exposed large islands with islands nearby were positively associated with Eider breeding abundance during the late period. Future conservation efforts should shift from site-specific conservation to population-specific management due to the shift in nest-site preference. Furthermore, the positive influence of gulls warrants the adoption of conservation measures taking interspecific interactions into consideration.
Duck–fish competition in boreal lakes – a review
Authors: Nummi Petri , Väänänen Veli-Matti , Holopainen Sari , Pöysä Hannu
Published: December 2023

Ducks share the aquatic environment with invertebrate-eating fish. Thus, competitive interactions may take place. Fish have been introduced to many formerly fishless lakes, which has profoundly affected the competitive and predatory relations in these waters. In this paper we review recent findings on duck–fish competitive interactions in boreal lakes. On a general level, analyses based on presence/absence data of fish have indicated that ducks can be negatively affected by fish.More rigorous studies where fish density has been considered have corroborated the pattern emerging from presence/absence studies. For the Common Goldeneye (Bucephala clangula) and Eurasian Perch (Perca fluviatilis), the effect of competition has been tested experimentally. In general, it appears that diving ducks such as Common Goldeneye, which forage in open water, are the most affected by fish, Common Teal (Anas crecca) is intermediate, whereas Mallard (A. platyrhynchos), which forage among the shore vegetation, is little affected. Likelihood or the strength of competition between ducks and fish may also depend on habitat productivity and structure. Numbers of invertebrates are higher among vegetation where there are less fish preying on them. Duck–fish interactions are important to take into account when planning wetland creation and restoration for ducks. There is also an urgent need to mitigate the effects of fish introductions in wetlands.
Colour morph does not predict brood size in the Booted Eagle
Authors: Martínez José , Calvo José , Jiménez-Franco María , Zuberogoitia Iñigo , López-López Pascual
Published: December 2023

Mechanisms regulating colour polymorphism remain largely unknown and detailed investigation is required to explore the biological consequences on population dynamics. This paper presents the first study of the possible connection between colour polymorphism and productivity in aBooted Eagle (Aquila pennata) population breeding in southeastern Spain. To that end we used 19 years of data of non-marked individuals. Atotal of 738 pale (91.6%) and 68 dark (8.4%) adult Booted Eagles were observed in our study area, including 57 territories. Our results suggest that colour morph of both sexes remained stable in the population over the study period. Although we found a higher number of offspring produced by parents exhibiting the dark morph than those of the pale morph, statistical differences were not significant. Hence, ourmodels showed that colour polymorphism was not a good predictor of Booted Eagles’productivity, although further research by capture-recapture analysis would be needed to explore the influence of colour variation on fitness components at individual level and its consequences at population level of long-lived species.
Peregrine Falcon (Falco peregrinus) may affect local demographic trends of wetland bird prey species
Authors: Tornberg Risto , Korpimäki Veli-Matti , Rauhala Pentti , Rytkönen Seppo
Published: December 2023

The demographic value of existing habitat can be affected by changes in predator populations. In Finland, wader populations increased when the Peregrine Falcon (Falco peregrinus) declined, due to poisoning by agricultural chemicals during the 1960–1970. Following regulation ofDDTusage, nesting Peregrinenumbers have increasedmore than tenfold, while wader populations concurrently declined. The “protection” hypothesis states that although top predators may negatively affect populations of primary prey species, they may benefit other species populations by suppressing activities of mesopredators, such as egg and chick predation.We studied diet preferences of Peregrine Falcons in south-west Finnish Lapland during a period of falcon population growth, based on indices of species consumption versus availability. Preferred and optimal sized prey species, excluding ducks, were equally abundant on bogs with and without Peregrines, and neither did the abundance of non-preferred or non-optimal sized birds differ between bogs with and without Peregrines. Thus, the protection hypothesis was supported for ducks. We found that preferred prey species significantly declined in numbers over time, while populations of non-preferred and non-optimal sized prey species declined less or remained stable, as expected if Peregrines would have direct negative effects on prey species. However, local effects were apparent when comparing local versus national trends of suitable and less suitable sized prey for the Peregrines.While the raptors’ role in the population declines of wetland speciesmust have increased after their recovery in the 1970s, this effect might be difficult to separate from other concurrent effects of habitat loss.
Are age and body condition associated
with habitat quality around avian song posts?
A test with male Bluethroats at a breeding site in Spain
Authors: Arizaga Juan , Alonso Daniel , Castro Alberto
Published: December 2023

We explored whether habitat characteristics surrounding the song posts that male Bluethroats (Luscinia svecica) use to attract females and defend their territoriesmight be associated withmales’quality, in terms of body condition and age (used here as a proxy of their experience).Datawere collected at Sierra de Béjar (province of Salamanca, centralwestern Spain). Overall, we characterized the habitat and captured 44maleBluethroats at their song posts in 2011 and 2012. The characteristics ofmaleBluethroats’song posts and their surrounding habitat were associated with both the birds’ age and body condition. Second-year Bluethroats were observed to sing in places with higher abundance of spiders as compared to older birds.Moreover,Bluethroats surrounded by a higher proportion of grasslands and with more Opiliones/spiders were found to carry more fuel.
Tawny Owl females of intermediate colour morph reproduce
better and increase in a local polymorphic population
Authors: Grašyte Gintare , Rumbutis Saulius , Dagys Mindaugas , Vaitkuviene Daiva , Treinys Rimgaudas
Published: December 2023

Individuals of the same population with differing melanin plumage colouration can respond differently through fitness to environmental stressors. In a local population of Tawny Owls (Strix aluco), we colloected individual-based data on nesting attempts of this well-known colour polymorphic species between 1985 and 2014. We studied whether body size, condition, demographic parameters and habitat around occupied nest sites differ among grey, intermediat and brown coloured females. The proportions of females belonging to each of the three colour morphs in the local population changed during the study period, with intermediate individuals becoming more frequent in the last decade. Females were similar in body size and achieved similar body condition during breeding irrespective of plumage colouration. Although most of the analyzed demographic parameters were not statistically significantly related to the colour morph, the intermediate owls raised more nestlings in a lifetime and tended to have higher recapture probability. We found little support for habitat and morph associations. In summary, we propose that the increase in intermediate Tawny Owl colour morphs in this local population is associated with their better reproductive performance compared to the other morphs.
Breeding parameter changes in two syntopic urban Sparrow species with contrasting population trends
Authors: Wegrzynowicz Andrzej
Published: December 2023

The number of House Sparrows (Passer domesticus) in urban populations has decreased considerably in recent decades in many parts of Europe, particularly in its western part. In Warsaw (Poland), between the 1970s/1980s and the 2000s a decline of almost 50% was recorded. During the same period, Tree Sparrows (Passer montanus), a species also known to have decreased in western Europe, increased significantly in Warsaw. This paper addresses the changes in breeding parameters of both species between the 1980s and the 2000s, i.e., in the period when their numbers changed significantly. Both species have advanced their breeding periods. Despite that the advancement was more significant in the House Sparrow, it did not appear to influence the number of breeding attempts per year, which increased in the Tree Sparrow. In addition, clutch size increased in the Tree Sparrow but not in the House Sparrow. In both species, the level of egg losses did not change, while the nestlings losses decreased, resulting in higher average brood productivity. The annual breeding productivity increased in both species due to fewer breeding losses, and in the Tree Sparrow due to a high number of broods per season. The results suggest that food availability for sparrow nestlings (likely arhtropod resources) in the urban habitats of Warsaw are sufficient to ensure both sparrow species a high level of breeding success. This contrasts with the conclusions of studies of urban House Sparrow populations in western Europe. the strong improvement in Tree Sparrow breeding productivity may be a factor that has determinen the growth of its population in recent times.
Nest tree characteristics of the old-growth specialist Three-toed Woodpecker Picoides tridactylus
Authors: Pakkala Timo , Tiainen Juha , Piha Markus , Kouki Jari
Published: December 2023

The Three-toed Woodpecker Picoides tridactylus is a mature and old-growth forest specialist but how the species uses trees for nesting in its breeding sites and whether cavity trees are a critical habitat feature is poorly known. We studied the nest tree characteristics of the species in a 170-km2 area in southern Finland during 1987–2016. The data included 538 nest trees of eight different species and 665 nest cavities in 86 territory areas. Norway spruce Picea abies was the predominant nest tree comprising 71% of all nest trees. Proportionally, deciduous nest trees were more common in moist forests on mineral soils and conifer nest trees more common in spruce swamps. The majority of nest trees (85%) were dead or decaying trees; higher numbers of dead deciduous nest trees were recorded than dead conifer trees. The mean diameter of a nest tree at diameter at breast height (DBH) was 29.4 cm and the mean height of a cavity hole was 5.1 m; size and height were significantly positively correlated. The proportion of deciduous nest trees was significantly higher (45%) in natural forests compared with other areas subjected to variable amounts of forest management, where the respective proportion was only 9–17%.
Large scale climate affects the timing of spring arrival but local weather determines the start of breeding in a northern Little Tern (Sternula albifrons) population
Authors: Pakanen Veli-Matti
Published: December 2023

In migratory birds, the timing of arrival to the breeding grounds can be affected by weather on the migration routes and breeding sites at arrival. Timing of breeding can be affected by arrival dates but also by local weather conditions during the pre-breeding period. Because long-distance migrants arrive and breed late in the season, weather is thought to be less important, but more information is needed especially from seabirds that are vulnerable to climatic effects. I used observation data from the Little Tern (Sternula albifrons), a long-distance migrant, made by bird watchers during 2006–2016 to examine whether their spring arrival to the breeding grounds in Finland is associated with the large-scale weather pattern (the North Atlantic Oscillation; NAO index) or local weather. In addition, I used breeding data to examine whether the start of egg laying is associated with the annual first arrival dates, local weather or the NAO index. Spring arrival was associated with large scale weather patterns rather than local weather conditions.
Does the Common Kingfisher (Alcedo atthis) select the most energetic fish prey?
Authors: Vilches Antonio , Miranda Rafael , Arizaga Juan
Published: December 2023

During the chick-rearing period, strategies of prey provisioning can have a decisive impact on several reproductive aspects. Adults can maximise their foraging effort by increasing the number of fish-prey brought to the nest per unit time and/or by catching more energetic prey, i.e. larger prey or prey with relatively higher caloric values. The Common Kingfisher (Alcedo atthis) is a fish-eating predator normally breeding in freshwater habitats. We collected data on fish-prey proportions found at nests (n = 10) and determined the caloric content of such fish-prey (6 species overall) in rivers in northern Iberia. The proportion of each fish-prey species in the nest was not correlated with the proportion of lipids, proteins or carbohydrates, nor with its caloric content.
Airspeed of the Song Thrush in relation to the wind during autumnal nocturnal migration
Authors: Sinelschikova Alexandra , Griffiths Martin , Vorotkov Michael , Bulyuk Victor , Bolshakov Casimir
Published: December 2023

Birds possess behavioural and physiological adaptations which permit them to minimize time and energy expenditure during migration in a broad spectrum of winds, for instance, by varying their airspeed. Nocturnally migrating birds were recorded by an optical-electronic matrix system, which permitted recording their images and flight parameters in the dark. Among medium size birds, Song Thrushes (Turdus philomelos) were identified by their silhouette, linear size, wing-beat pattern, and phenology. The equivalent airspeed at sea level (VEq) of the observed thrushes without wind assistance (mean value 14.4 m/s) was close to the maximum range speed (Vmr) predicted from flight mechanical theory. This indicated an energy-selected migration strategy of the thrushes in autumn. The characteristic speed Vmr is wind-dependent: it increases with increasing velocity of head- and sidewinds. The airspeeds of the Song Thrushes showed a similar pattern of wind-dependence.
Ecological factors affecting foraging behaviour during nestling rearing in a high-elevation species, the White-winged Snowfinch (Montifringilla nivalis)
Authors: Brambilla Mattia , Scridel Davide , Sangalli Beatrice , Capelli Federico , Pedrini Paolo , Bogliani Giuseppe , Rubolini Diego
Published: December 2023

During breeding, parents of avian species must increase their foraging efforts to collect food for their offspring, besides themselves. Foraging trips are thus a key aspect of the foraging ecology of central-place foragers when rearing their offspring. However, studies of the foraging ecology of high-elevation specialists inhabiting harsh environments are scarce. Here we report for the first time quantitative information on ecological determinants of foraging trips in the White-winged Snowfinch (Montifringilla nivalis), a high-elevation specialist threatened by climate warming. We focused on seasonal, meteorological, habitat and social factors affecting distance and duration of foraging trips performed during nestling rearing, recorded by visual observations in the Italian Alps. Based on 309 foraging trips from 35 pairs, we found that trips lasted 6.12 min and foraging areas were located at 175 m from the nest site on average.
Book review on Darwin comes to town: How the urban jungle drives evolution by Menno Schilthuizen (2018)
Authors: Suhonen Jukka
Published: December 2023

Menno Schilthuizen (2018): Darwin comes to town: How the urban jungle drives evolution. — Picador, 293 pages.
Complex habitat patterns create unpredictable nest predation risk – an artificial nest experiment
Authors: Pass Eliisa , Lodjak Jaanis , Mägi Marko , Lõhmus Asko
Published: December 2023

Although birds might increase nesting survival by selecting safe sites, nest predation is a major limiting factor in natural bird populations. We investigated how forest structure, predator distribution, and nest location contribute to nest predation risk, and whether lower predation probabilities characterize formerly “safe” sites. We distributed 304 artificial ground and tree nests in a forest landscape, following the previous year locations of forest grouse observations (with and without broods). We modelled nest predation incidence using generalized mixed models; we also identified potential nest predators by tooth/bill marks on plasticine eggs. We found complex habitat effects: nest predation depended non-linearly on the stand age (low risk in post-clear-cut stands; peak values in middle-aged stands) and there were no simple relationships with predator proximity or nest concealment. Predation probabilities were higher in tree nests than in ground nests, and did not differ in the locations where broods had been observed or not.
Sexual size dimorphism in the Common Crane, a monogamous, plumage-monomorphic bird
Authors: Alonso Juan C. , Bautista Luis M. , Alonso Javier A.
Published: December 2023

Male-biased sexual size dimorphism (SSD) is common and related to male mating success in polygynous birds, but also occurs in monogamous species, in which sexual selection can be strong. In these species, SSD in morphological traits not directly related to reproductive function, such as locomotory or feeding structures, has remained difficult to explain. We present the first biometric data of an archetypal monogamous bird, the Common Crane (Grus grus), based on molecular sexing techniques. Males were heavier and larger than females, with weight showing the largest SSD, followed by wing, central toe, and head length in adults and juveniles. These sexual differences were also present in nine crane pairs where both adults were measured, with values being positively correlated between pair members, suggesting assortative mating and female choice as the main mechanisms driving the evolution of SSD.
Population changes in the declining Turnstone (Arenaria interpres) and other waders in the northern Baltic Sea based on past and current breeding observations
Authors: Von Numers Sebastian , Öst Markus , Von Numers Mikael
Published: December 2023

Many waders are declining based on winter surveys, but assumed trends need to be validated against changes in breeding numbers. Comparing breeding population changes between threatened and non-threatened closely related species allows assessment of the species-specificity of threats. To identify biogeographical and biological correlates of population trends in declining Ruddy Turnstones (Arenaria interpres) and four other waders in the Archipelago Sea, SW Finland, we re-censused 209 islets in 2015–2018 hosting breeding Turnstones in the late 1980s–early 1990s. We used island-specific geographical variables and pair numbers of five gull and three tern species as predictors in species-specific logistic regression models of breeding probability. The number of islands with Turnstones (29) decreased by 86.1%. The proportion of islands with breeding Ringed Plovers (Charadrius hiaticula) significantly increased, while there were no trends for Redshanks (Tringa tetanus), Oystercatchers (Haematopus ostralegus) or Common Sandpipers (Actitis hypoleucos). However, the proportion of islands with more than one breeding pair of Oystercatchers increased. Ruddy Turnstone breeding occurrence was positively associated with Arctic (Sterna paradisaea) and Caspian Tern (Hydroprogne caspia) breeding numbers, island exposure and area, and negatively associated with forest area and Common Tern (S. hirundo) breeding numbers. Probable reasons for the decline are the presence of American mink (Neovison vison), a significantly declining proportion of islands with breeding Arctic Terns and natural vegetation succession. Our study highlights that population trends vary greatly between waders, but confirms the population decline of the Turnstone, now increasingly confined to exposed thinly scattered islands. Maintaining viable populations of small larids is crucial in improving its conservation status
Offspring sex ratio and partially asynchronous hatching in the Little Bittern (Ixobrychus minutus) population in south-western Slovakia
Authors: Trnka Alfréd
Published: December 2023

Birds are one of the best-studied animal groups in Europe. Despite this, there are several bird species, including the Little Bittern (Ixobrychus minutus), of which the breeding biology is still little known. Here, I examine the sex of offspring in relation to hatching order, the degree of hatching asynchrony and some other aspects of nesting biology (such as breeding phenology, clutch size, egg and nestling survival) of the Little Bittern in the south-western Slovakian population. Egg-laying occurred from 5 May to 10 July, but the majority of clutches were initiated in May. Mean clutch size was 5.2 ± 0.92 (SD) eggs. Parents initiated full incubation predominantly after laying the third egg (86.4% of cases) of the clutch, which led to only partially asynchronous hatching of eggs. However, no evidence was found for offspring sex ratio adjustment according to hatching order. Nevertheless, survival rates of eggs and nestlings were relatively high (80.9% and 94.3 %, respectively). The possible causes of observed patterns are discussed.
La naturaleza del derecho de acceso a la información pública
Authors: Guichot Reina Emilio
Published: December 2023

Desde hace décadas se debate a nivel mundial en el plano judicial y doctrinal sobre la naturaleza del derecho de acceso a la información pública. En la actualidad, puede hablarse de una decantación mayoritaria hacia su consideración como derecho fundamental, sea autónomo, en las cartas de derechos fundamentales más recientes, sea como parte del contenido de la libertad de información, en las más veteranas. De ello damos cuenta en la primera parte de este trabajo, poniendo especial atención en las conclusiones extraídas del Derecho internacional y europeo, pues, conforme dispone el artículo 10.2 de la Constitución Española, “las normas relativas a los derechos fundamentales que la Constitución reconoce se interpretarán de conformidad con la Declaración Universal de Derechos Humanos y acuerdos internacionales sobre la misma materia ratificados por España”. Prestaremos especial atención a la nueva jurisprudencia sobre el tema emanada del Tribunal Europeo de Derechos Humanos.
En España, el debate, tanto a nivel político como doctrinal, ha sido particularmente intenso, muy especialmente a partir de la tramitación, aprobación y entrada en vigor de la Ley 19/2013, de 9 de noviembre, de transparencia, acceso a la información pública y buen gobierno. También nuestros tribunales internos se han pronunciado al respecto.
Sobre ello se reflexiona en la segunda parte de este trabajo para llegar a unas conclusiones sobre la naturaleza del derecho de acceso y la dificultad del encaje entre la dogmática tradicional de la libertad de información y el derecho de acceso a la información en la sociedad tecnológica en la que vivimos.