Ornis Fennica is a peer-reviewed, international, diamond open access ornithological journal published by BirdLife Finland.
Assessing abundance and habitat preferences of Goldcrest Regulus regulus and Firecrest Regulus ignicapilla using passive acoustic monitoring and point-count surveys in temperate forest ecosystem in Poland
Passive acoustic monitoring (PAM) provides new opportunities for assessing bird abundance and habitat preferences, yet its performance relative to traditional point-count surveys (PCO) remains insufficiently tested, especially for quiet and inconspicuous forest passerines. We compared the vocal activity and habitat associations of the Goldcrest Regulus regulus and Firecrest Regulus ignicapilla in a temperate forest ecosystem using PAM-derived and PCO-based indices. Across 30 monitoring points in the Romincka Forest (Poland), PAM yielded >33,000 recorded songs and revealed strong spatial variation in both species. Vocal activity measures obtained from PAM correlated positively with PCO detections and territories, confirming the reliability of PAM as a complementary abundance indicator. Goldcrest vocal activity showed a strong positive association with the proportion of coniferous trees—especially spruce—and with local tree-species richness, reflecting the species’ affinity for structurally diverse conifer-dominated stands. In contrast, Firecrest abundance was unrelated to forest structure in PAM data, while PCO detections indicated avoidance of pine and lower activity in species-rich stands. No significant relationship with stand age was observed for either species. The weak interspecific correlations in activity parameters highlight their distinct ecological niches despite overlapping ranges. Based on PCO Goldcrests proved to be more abundant, with a territorial ratio of 3:2 compared to Firecrests. Our study demonstrates that PAM effectively captures variation in abundance and habitat selectivity of both Regulus species and provides a scalable, efficient complement to traditional surveys in temperate forest ecosystems.
Copyright (c) 2022 Karol Kustusch, Dawid Cząstkiewicz, Andrzej Wuczyński https://creativecommons.org/licenses/by/4.0
Rise of the Eagle Owl population due to rat-rich refuse dump sites and fall when closing them: a large-scale long-term “supplementary feeding experiment”
Food-supplementation experiments conducted on terrestrial vertebrates have usually shown the importance of food as an agent in increasing reproductive success. However, to date, the number of large-scale food supplementation experiments carried out on top predators has been limited. The Eurasian Eagle Owl (Bubo bubo) is the largest nocturnal avian predator in the boreal and temperate regions of Eurasia. Here, we study the diet composition and breeding success of this top predator in relation to the location and distance to rubbish dumps, which sustain large numbers of brown rats Rattus norvegicus, one of the main prey items for owls. The number of these rubbish dumps (hereafter dumps) increased in Finland during the period between the 1960s and the 1990s, whereafter their number was steeply reduced, leading to a remarkable decline in rat populations. A similar trend in the Eagle Owl population largely followed this development, raising the question of whether this country-wide "supplementary feeding experiment" was behind this phenomenon. The proportion of rats in the diet of the owls was high, on average, 70% of prey items near the dumps decreasing to around 10–15% at a 6–7 km distance from the dumps. Correspondingly, the number of 3–4-week-old offspring declined in relation to the distance from the dump, so that 0.5 less chicks were recorded at a distance of 10 km from the dump. During the study, the overall density of nests near the dumps was 2.7 times higher than those recorded further away. The availability of extra food material within the dumps (and rats therein) probably induced an increase in the Finnish Eagle Owl population, which saw a decline after dumps were closed.
Copyright (c) 2022 Risto Tornberg, Kauko Huhtala, Heimo Mikkola, Jere Tolvanen, Jari Valkama, Erkki Korpimäki https://creativecommons.org/licenses/by/4.0
Estimating the population and related dynamics of the cave-dwelling Edible-nest Swiftlet in the Andaman Islands, India
Apodids (Swifts and Swiftlets) are among the under-studied bird species. They are hard to identify, and their breeding habitats are inaccessible, making studying their population estimation and related dynamics challenging. In this study, we aimed to estimate the populations using the capture-mark-recapture (CMR) and nest count methods. Conducted at the Baratang cave complex in the Andaman Islands, our study used stratified sampling to choose 12 study caves based on the breeding population for capture and recapture in all possible caves occupied by Edible-nest Swiftlet (Aerodramus fuciphagus). The use of the Lincoln Index to estimate the populations of the Edible-nest Swiftlet in each cave by analyzing the capture-mark-recapture data and using the program MARK with the Live Recaptures. The Lincoln Index and total population count estimated 486 and 505 birds, respectively, with no significant difference (p > 0.05). The best-fit model indicates that the annual survival rate was consistent throughout the study period (0.97–1.00), and the capture probability was 0.35 ± 0.02. The study evidently showed that using only one method is inadequate for accurately estimating the Edible-nest Swiftlet populations. The CMR method is recommended as an alternative when it is necessary to understand related population dynamics, and the nest and roost count methods are not feasible. The study confirms the effectiveness of the CMR method when used in combination with other traditional methods.
Copyright (c) 2022 Prathamesh Gurjarpadhye, Dhanusha Kawalkar, Ram Pratap Singh, Shirish Manchi https://creativecommons.org/licenses/by/4.0
Citizen science perceptions into the distribution and impacts of the Common Myna (Acridotheres tristis) in Jordan
The Common Myna (Acridotheres tristis) is a globally recognized invasive alien species with documented ecological and social impacts. This study employed a citizen science approach to investigate the distribution and perceived ecological and economic effects of the Common Myna in Jordan. An online questionnaire yielded 201 valid responses from all 12 governorates, of which only 50.2% of respondents who recognized the species were included in the subsequent data analysis. Reports from 113 localities indicated that the species is concentrated in urbanized areas of northwestern Jordan. Increased sightings since 2019 suggest population growth and continued expansion across human-modified landscapes. Increased occurrences near protected and in agricultural areas raise ecological concerns. Respondents identified competition with native birds as the main impact, while effects on crops and human health (e.g., noise) were perceived as minor. Urban expansion and food waste were viewed as key drivers of the spread. Beyond data collection, the survey also functioned as an awareness tool, highlighting the dual value of citizen science for both monitoring and education. Overall, the study highlights the importance of implementing coordinated management measures that integrate regulation, waste management, and public awareness.
Copyright (c) 2022 Ehab Eid, Fares Khoury https://creativecommons.org/licenses/by/4.0
Mismatch between planned and realized harvests: integrating hunter demography, harvest records and waterbird monitoring to inform game bird management in Poland
Bird hunting, with deep historical and cultural significance, faces sustainability challenges, particularly for migratory species. In Poland, the calibration of annual harvest ceilings (quotas) relative to realized harvest and current abundance is debated. This study: (i) examined the Słupsk Hunting District by comparing district annual quotas (plans) with realized harvest, (ii) examined alignment between nationwide mid-winter (January) goose counts and season-long district harvest totals (Sep–Jan), and (iii) surveyed hunter demographics and preferences. Results showed significant discrepancies, with realized harvest totals well below planned levels (median = 11%). Goose abundance correlated moderately with harvests (r = 0.647, p < 0.0001), though phenological (mid-winter vs season-long) and effort mismatches limit interpretations. Among the hunters surveyed, more than one-third were over 45 years of age (36.2%). Most of these hunters chiefly targeted ducks (ca. 80% of respondents) and, to a lesser extent, geese (ca. 40%). These findings highlight that the maximum set quotas (ceilings) often exceed locally attainable harvest and emphasize the need for standardized monitoring, transparent quota recalibration and adaptive harvest strategies, and policy reforms to align hunting practices with ecological realities (current abundance and seasonal availability under observed effort), ensuring viable and sustainable wildlife management in Poland.
Copyright (c) 2022 Kinga Piórkowska, Michał Szkudlarek, Łukasz Jankowiak https://creativecommons.org/licenses/by/4.0
Elevational distribution of bird assemblages in the Western Carpathians is mainly driven by floristics, climate and productivity
The Carpathian Mountains have one of the largest remaining primeval and natural forests in the European Union and have been little studied in terms of biogeography. In this paper, we consider the elevational distributions of bird assemblages in the Western Carpathians and the environmental factors that drive them. We used censuses performed by territory mapping methods and explanatory data from 38 study sites (139-year samples) along an elevational gradient from lowland to subalpine zones. We analysed these data matrices with bootstrapped cluster analyses and indirect and direct correspondence analyses (DCA, CCA, CO-CA). Cluster analyses of Euclidean distances from the presence/absence, density, and dominance matrices produced differing numbers of significant clusters (8, 6, 7) corresponding to six, four and five elevational belts. Only three elevational zones—lowland, mountain, and subalpine—were consistent in all classifications. Explanatory variables, i.e. floristics, precipitation, temperature and productivity, had the overall highest rank in explaining the variance in canonical correspondence analysis (CCA) ordinations. Floristics and woody plant species dominance were strong predictors of the elevational pattern of bird assemblages in co-correspondence analyses (CO-CA). Our results support the Clementsian concept of significant and discrete assemblages, not tied to fine habitat types, yet rather defined along wide habitat scales.
Copyright (c) 2022 Martin Korňan, Ľudovít Kocian, Karel Pavelka, Rudolf Kropil, Peter Lešo, Jan Pavelka, Katarína Mikulová, Vladimír Šebeň https://creativecommons.org/licenses/by/4.0
Morphological differentiation of breeding and migratory Linnets Linaria cannabina in eastern Spain
This paper aims to assess whether breeding and migratory populations of Linnets (Linaria cannabina) in eastern Spain show morphological differentiation and whether migration timing correlates with morphometric traits. For that, we collected biometric data from over 4,000 Linnets captured in breeding sites and at coastal migratory stopovers in Castellón, Spain. We used Principal Component Analyses and General Linear Models to test for differences across age, sex, breeding status and season. Morphological traits varied significantly between first- and second-calendar-year birds, especially feather and skeletal measurements. Migratory individuals showed a larger body size (compatible with a more northern origin according to Bergmann’s Rule), proportionally higher and wider bills (which might reflect geographical trophic preferences), and a higher wing-tail ratio (compatible with a longer migration distance like morphology). Within each migration season, birds passing later tended to have traits associated with a more northern origin, suggesting population-level differences in migration phenology. Morphometric variation in Linnets reflected both migratory strategy and passage timing, highlighting the utility of biometric analyses for understanding migration dynamics and population structure in passerines.
Copyright (c) 2022 Juan Arizaga, Salvador Escamilla, Joan Castany, Ana M. Barragan, Rafael Silvestre, Pascual Timor, Benjamín Pupla, Gerardo Arzo, Batiste Borrás https://creativecommons.org/licenses/by/4.0
Local variation in sex ratios in three species of wintering ducks: the need for large-scale sampling
This study investigates the hypothesis that site characteristics and flock size influence the sex ratios of wintering ducks by examining three species: the Mallard (Anas platyrhynchos), the Goldeneye (Bucephala clangula), and the Long-tailed Duck (Clangula hyemalis) in the Gulf of Gdańsk, southern Baltic. Birds were counted in mid-January along approximately 160 km of shoreline in the western part of the Gulf of Gdańsk and the estuarine sections of the Vistula River on the southern Baltic coast. Only flocks in which the sex of all individuals was identified were included in the analysis. The sex ratios of the three study species varied across the five habitat types within the study area but did not vary with species-specific flock size. In Mallards the lowest proportion of males was recorded along the open seacoast and municipal beach, suggesting that these areas are primarily occupied by paired birds. The higher proportion of males at other sites is likely due to the shift of unpaired individuals to these locations, where the overall number of this species is the highest. In the Goldeneye the highest percentage of females was observed in the most sheltered areas, while the lowest percentage, alongside low individual numbers, occurred along the open seacoast. These patterns suggest that Goldeneye density and sex ratio are influenced by female tolerance to adverse weather conditions, as this species shows the greatest size difference between males and females among the species studied. Long-tailed Ducks exhibited a more uniform sex ratio across the study area, likely due to their frequent movements to access areas with abundant food resources. This study highlights spatial variations in duck sex ratios within a single water body and underscores the need for large scale sampling to obtain representative sex ratio estimates.
Copyright (c) 2022 Włodzimierz Meissner, Dorota Kozakiewicz https://creativecommons.org/licenses/by/4.0
Crested Tits prefer pine forest but not mature forest: insights from an early spring passive acoustic survey
The Crested Tit (Lophophanes cristatus) is a relatively common species in Finland but is declining likely due to increasing anthropogenic pressures and habitat degradation. Here, we study habitat preferences of Crested Tits in Southwest Finland. We conducted a passive acoustic survey of the species’ presence and absence just prior to breeding in spring 2020 based on 1-week recordings made in 285 forested sites that were about 1 km from each other. We found that Crested Tits prefer a higher amount of pine foliage within a 100-meter radius but not at 400-meter radius. Contrary to our expectation, Crested Tit occurrences showed no preference for mature forests. Additionally, we found that Crested Tits avoid proximity to houses. No habitat preference was evident at the scale of 400-meter radius, probably because a significant proportion of habitat types are not used by the species at this scale. Lastly, despite the overall decline in the Crested Tit population in Finland, we found Crested Tits to be present in 68% of our sites, emphasizing the robustness of passive acoustic surveys as a valuable tool for studying avian habitat preferences and population monitoring. The findings contribute to our understanding of Crested Tit ecology in the face of habitat degradation and declining populations, offering insights for conservation measures in this region.
Copyright (c) 2022 Pegah Hamedani Raja, Daniele Baroni, Toni Laaksonen, Jon Egbert Brommer https://creativecommons.org/licenses/by/4.0
Migratory protogyny and condition-dependent arrival in Icelandic Red-necked Phalaropes
In many migratory birds, arrival at breeding grounds is sexually asynchronous. This pattern is often explained by the idea that early arrival benefits the sex under stronger sexual selection by improving access to mates through territoriality. However, in species where females arrive first and are non-territorial, this explanation falls short. One alternative is that early-arriving females are simply in better condition. Here we report, for the first time, evidence of migratory protogyny in the Icelandic population of Red-necked Phalaropes (Phalaropus lobatus), a shorebird with reversed sexual dimorphism. We also present the first direct test of the condition-dependent hypothesis in a protogynous species, using arrival data, morphometric measurements, and leukocyte profiles. Although females arrived significantly earlier than males, we found no evidence that early arrival was linked to superior body condition. Leukocyte profiles did not suggest marked sex differences either, although we had insufficient statistical power to test this. Our results point instead to the role of sex-specific migratory strategies and intrasexual competition in shaping arrival timing. With its unique life history, P. lobatus offers a powerful model for studying the evolution of sex-biased migration. We encourage further research integrating fine-scale tracking, reproductive monitoring, and physiological data to better understand ...
Copyright (c) 2022 Oscar García Miranda, Pedro Rodrigues, Tamás Székely, Renáta Szarvas, José O. Valdebenito https://creativecommons.org/licenses/by/4.0
Winter site fidelity of the Great Tit (Parus major) revealed by recaptures of individuals roosting in nest-boxes
Birds often return to the same locations where they have previously bred successfully or survived the winter, demonstrating site fidelity. This behaviour extends beyond breeding sites to include roosting and feeding areas, with individuals frequently recaptured at the same locations across years. In this study, we investigated the winter site fidelity of Great Tits and analysed how various factors (winter temperature, sex, age, site, date of first capture, and winter season) influence recaptures within and between winters. We monitored individuals roosting in nest boxes at two sites within Bratislava city, western Slovakia. Within-winter site fidelity was observed in 45.89% of birds (N = 146), meaning these individuals were recaptured at least once during the same winter at the same site. Among the tested variables, age and date of first capture in the season significantly influenced within-winter site fidelity. Older birds and those captured earlier in the season were more likely to be recaptured in the same winter. Between-winter site fidelity, defined as birds ringed and later recaptured in a different winter, was observed in 12.92% of 178 Great Tits. Age was a significant factor, with older individuals being more likely to be recaptured in subsequent winters. Furthermore, birds that were recaptured more often during their first winter had a higher likelihood of being recaptured in later winters, suggesting consistent long-term site use.
Copyright (c) 2022 Martin Matejka, Kristína Abrahámovičová, Hana Tomanovičová, Martin Gera, Zlatica Országhová, Lucia Rubáčová https://creativecommons.org/licenses/by/4.0
The selective consumption of European ivy (Hedera helix) berries by the Common Blackbird (Turdus merula)
Seed dispersal of plants affects the spatial structure and population dynamics, contributing to ecosystem functioning. Birds are among the most important seed dispersers. Preferences of birds in fruit and berry consumption are potentially significant selective pressures on the evolution of fruit traits that affect plant fitness. European ivy (Hedera helix) is a widespread deciduous species in Europe and the Common Blackbird (Turdus merula) is important seed disperser. This study investigates blackbird feeding preferences for specific sizes of ivy seeds. Field data was collected in a small settlement east of Simferopol city in Crimea and included a collection of reference seeds gathered from plants and seeds found in bird excretions. The length of the major axis, minor axis, and aspect ratio were measured, and statistical analysis was performed. The length of the major and minor axes of seeds consumed by blackbirds was higher compared with the reference collection, the aspect ratio was the opposite. Evidence of size differences could suggest weak effect of selective consumption of blackbirds on seed shape. This research extends our knowledge of the ecological relationship between frugivorous birds and plants and the role of birds in directional selection in a particular locality.
Copyright (c) 2022 Volodymyr Kucherenko https://creativecommons.org/licenses/by/4.0
A helpful and long-overdue resource for work with mountain birds
The newly released textbook, Ecology and Conservation of Mountain Birds (edited by Chamberlain, Lehikoinen & Martin), provides a comprehensive review of the latest knowledge in alpine ornithology. It summarizes the combined knowledge of over 50 subject experts and serves as an excellent reference guide for professionals and students. Here, the layout and contents of the book are reviewed and an unbiased general assesment of the contents are provided. As the global environment continues to see unprecedented changes, this work should serve as a groundbreaking benchmark describing the state of our mountain birds.
Copyright (c) 2022 Theodore Squires https://creativecommons.org/licenses/by/4.0
Effects of predation pressure and nest-site selection on the breeding success of terns in a Finnish archipelago
Studying and quantifying the breeding success of species can help to understand population trends and provide conservation guidance. Here, we studied the breeding success of Arctic Tern (Sterna paradisaea) and Common Tern (Sterna hirundo) colonies in a Natura 2000 site of the Western archipelago of Finland aiming to understand which factors related to nest-site selection and predation pressure best explain breeding success. We monitored 72 tern nests at 4 colonies and observed them during standardized monitoring sessions to record predation attacks on the tern nests. We ran generalized linear models to determine the factors which impact breeding success (hatching and fledging success). Hatching success was high across the 4 colonies with 69% of the eggs hatching, whereas fledging success was low with only 1 colony producing 14 fledglings while all other colonies had zero fledglings surviving (12% total fledging success). Regarding nest-site selection, our results demonstrate that a greater proportion of vegetation cover increases breeding success, likely through better nest concealment against predators. Nests in smaller colonies with a higher nest density and located closer to the colony center also produced more hatchlings and fledglings. Most predation likely happened during the chick stage, while our extrapolation predicted that predation accounts for at least 94% of all chick losses, indicating that predator control would aid breeding success of tern colonies in West Finland substantially.
Copyright (c) 2022 Enzo Degot, Ralf Wistbacka, Konsta Kaasalainen, Aleksi Lehikoinen, Laura Bosco https://creativecommons.org/licenses/by/4.0
GPS-tracking reveals winter short-stopping and large differences in individual migratory distance among Greylag Geese (Anser anser) breeding in Denmark
The exponential increase in the ‘NW/SW European Greylag Goose population’ (NGGP) has created demands for more precise estimates of the national breeding populations and improved understanding of their movements to support its effective management. Increased NGGP abundance has been associated with a northeast-ward shift in wintering centre of gravity, suggesting major changes in migratory and wintering patterns. Greater numbers of wintering Greylag Geese wintering numbers in Denmark could originate from increases in the Danish breeding population showing a more sedentary habit and/or from a higher incidence of “winter short-stopping” by birds from elsewhere. Data from the first 16 Greylag Goose deployed with GPS/GSM tracking collars in 2021 and 2022 were used to test the hypothesis that birds in newly colonised Danish breeding areas were more sedentary than the long-distance migratory geese in traditional nesting areas. Contemporary migration patterns showed that some Danish breeders (including examples from newly colonized breeding areas) still migrate to their traditional wintering quarters in southern Spain, but most tagged Greylag Geese stayed in Denmark throughout the annual cycle. These data also provided the first evidence of the occurrence of winter short-stopping among individual Danish Greylag Geese, which after one winter in Spain subsequently wintered in Denmark and the Netherlands, indicating that some individuals can shift between new wintering areas every autumn. Overall, these results show that while most Danish summering Greylag Geese are now largely resident within Denmark, some move to Germany and the Netherlands and a few still undertake the traditional long migration to southern Spain, making assignment of breeding provenance to migrating birds challenging.
Copyright (c) 2022 Henning Heldbjerg, Kevin K. Clausen, Lei Cao, Anthony David Fox https://creativecommons.org/licenses/by/4.0
Assessing avian incubation behavior in response to environmental pollution with temperature-humidity loggers
The negative impact of environmental pollution on avian physiology and breeding success is well documented. However, pollution-related behavioral changes during reproduction remain underexplored, despite behavior often being one of the earliest indicators of environmental disturbances and having significant life-history consequences. For example, altered food availability in a polluted environment could potentially perturb the incubation behavior of income breeders. These birds typically alternate between staying in the nest and heating eggs (on-bout) and taking foraging trips (off-bout). In this two-year study (2020 and 2022), we investigated how the incubation behavior of an insectivorous passerine, the pied flycatcher (Ficedula hypoleuca), varied with environmental pollution levels around a Cu-Ni smelter. Additionally, we compared two different metrics – temperature and humidity within the nest – to evaluate their use as indicators of incubation rhythm. We found that temperature- and humidity-based incubation rhythm parameters correlated, but those based on humidity matched better the true incubation behavior documented by simultaneous video recording. This was because the humidity curve showed a more immediate and intensive response to the female's incubation behavior. Birds in the polluted area took slightly more (11%) but shorter (11%) off-bouts, possibly reflecting smaller energetic constraints or better food availability in the polluted area. However, we found no difference in total incubation intensity between polluted and control areas, with F. hypoleuca females incubating their eggs 75% of the daytime in both environments. Hence, incubating females in the polluted area did not allocate more time for gathering their energy reserves than the birds in the control area, and there was also no difference in the hatching success. Our study is the first to use humidity variation to record incubation rhythm, and our results indicate that measuring humidity inside the nest is a promising technique to test and develop further. For example, further studies are needed to test if this method would work in different types of nests. From an environmental protection standpoint, our results also contribute valuable insights to the relatively limited information on pollution-related behavioral changes.
Copyright (c) 2022 Noé Freyssinge, Maria Perkkola, Lyydia Leino, Miia Rainio, Tapio Eeva https://creativecommons.org/licenses/by/4.0
Survival estimates of GPS-tagged adult Golden Eagles (Aquila chrysaetos) breeding in Finland
Adult survival estimates are important for assessing population status and viability and for investigating the role of different anthropogenic effects on their variation. Currently, the rapidly increasing wind power poses a new and severe threat to survival of large raptors. Between 2011–2024, we monitored 26 Golden eagles (Aquila chrysaetos) using Global Positioning System tracking devices in Finland, on territories where wind-power plants are currently absent and eagles are not subject to increased mortality from wind power plant collisions. Using the accumulated tracking data, we constructed individual capture histories on a monthly basis and adult survival rates using known-fate models in program MARK. We also review published adult survival estimates of Golden Eagles reported throughout their range for relative comparison. Monthly adult survival in our study area was 0.9933 (0.9854–0.9970) which translates to annual survival of 0.924 (0.838–0.965). We found eight studies reporting survival estimates, which ranged from 0.860 to 0.975 with a mean of 0.928. Thus, adult survival rates of Golden Eagles breeding in northern Finland, that are not affected by wind power plants, are high as expected for a viable population and very close to the mean estimated from other Golden Eagle populations. Maintaining high adult survival rates will be key to Golden Eagle population stability with expanding wind energy development in Finland.
Copyright (c) 2022 Hannu Tikkanen, Veli-Matti Pakanen, Olli-Pekka Karlin, Jouni Lamminmäki https://creativecommons.org/licenses/by/4.0
Proximity of shrub nests to ground nests increases the chance of ground nest predation
In nature, ground-nesting birds rarely nest under an active shrub nest of another species. In the case of the proximity of the two nest types, we assumed that if a nest predator finds one nest, it will most likely rob the other nest as well. To test this, we exposed artificial nests with one quail and one plasticine egg on shrubs and underneath on the ground, in oleaster shrub rows and forest edges. We found a higher predation on ground nests than on shrub nests in both habitats. More importantly, predation events in shrub nests resulted in a higher predation of more concealed ground nests too. Our results suggest that proximity of two nest types can be detrimental to predation pressure, especially in forest edges.
Copyright (c) 2022 Jenő J. Purger, Kornélia Kurucz, Dragica Purger, Péter Batáry https://creativecommons.org/licenses/by/4.0
Home range sizes and nychthemeral habitat uses by the Northern Shoveler (Spatula clypeata) on prenuptial stopovers in Vendée marshes, western France
The wetlands of Marais breton (MB) and Marais poitevin (MP) on the French Atlantic coast are commonly used by several duck species, especially as stopover sites during the prenuptial migration. Understanding the ecological requirements of Anatidae at spring stopover sites is important to define appropriate management actions that might have a carry over effect on the subsequent reproduction success. This study focused on the Northern Shoveler (Spatula clypeata), a species that regularly visits the two marshes during spring and fall migrations and is highly dependent on freshwater invertebrates as the food resource. Fifteen Northern Shovelers were equipped with GPS/GSM tags and monitored during their stopover in both marshes in 2020 and 2021. The aims of the study were to understand the habitat use on stopover sites and relate home range (HR) size with characteristics of the feeding habitats (such as freshwater invertebrates’ density and diversity). The HR area of the studied individuals was mainly constituted of ponds in MB (83% of the HR) and wet meadows in MP (71% of the HR). The Northern Shovelers equipped with tag spent more than 72 consecutive hours in 31 wetlands, using them during the day, at night or all day. The diurnal visited sites were deep ponds that were sparsely vegetated and dominated by microcrustaceans, whereas the nocturnal visited sites were wet meadows or ponds with high aquatic vegetation cover and high invertebrate taxonomic diversity. The 31 described sites appeared to be rich in freshwater invertebrates, with no significant difference in invertebrate densities between the diurnal and nocturnal sites. HR sizes were highly homogenous between the two study sites (MB and MP), between sexes or between age classes. In conclusion, according to this study, an appropriate HR for the Northern Shoveler at spring stopover is 8.49 ± 5.95 km² (mean ± standard error).
Copyright (c) 2022 Axelle Moreau, Clément Rousseau, Pierrick Bocher, Christine Dupuy, Sébastien Farau https://creativecommons.org/licenses/by/4.0
Apparent survival and dispersal in a White-throated Dipper (Cinclus cinclus) population from northern Iberia
River systems are some of the habitats most drastically affected by climate change. Consequently, many riparian species are amongst the most threatened living organisms worldwide, making riparian areas a conservation priority. Demographic analyses destined to improve our comprehension of the population dynamics of riparian species are crucial in this context. The present work analyses the spatio-temporal demographic dynamics of a presumably well-preserved White-throated Dipper (Cinclus cinclus) population from northern Spain. Using multistate models where we considered the effects of factors such as mean water flow in winter, age, sex, hydrographical basin of origin and hatching date, we found that the population had a constant annual dispersal rate (ψ = 0.038; 95% CI: 0.022–0.065). The mean apparent survival of Dippers from first-order clutches was 0.18 (95% CI: 0.12–0.22), whereas for those hatched in second-order clutches was 0.07 (95% CI: 0.03–0.15). The mean annual apparent survival for adults was 0.64 (95% CI: 0.56–0.70). Although apparent survival varied from year to year, we found no effect of the average winter flow on this parameter. Recapture probability (p) varied among basins, probably reflecting a heterogeneous sampling effort. In conclusion, using multistate models were found that Dippers from three adjacent river basins in northern Spain had a very short-range natal dispersal rate, and a breeding dispersal close to zero, a trait that could be different from findings in other zones of Spain, where dispersal rates seem to be much higher.
Copyright (c) 2022 Aitor Galarza, Luis Betanzos-Lejarraga, Juan Arizaga https://creativecommons.org/licenses/by/4.0
A new contact zone in the Chiffchaff distribution range: Caucasian and European subspecies meet each other in the south of Russia
The study of contact zones between closely related taxa of animals sheds light on many important issues of evolution biology and taxonomy. Several such zones were described earlier within the huge distribution range of the chiffchaff species complex (Phylloscopus collybita). We have documented for the first time the existence of a new contact zone between Caucasian (Ph. c. caucasicus) and European (Ph. c. abietinus) subspecies of the Chiffchaff in Ciscaucasia (southern Russia). We predicted the occurrence of hybridization between these subspecies belonging to the same group of “greenish” chiffchaff. In eastern Ciscaucasia, a population was found in which the abietinus and caucasicus haplotypes co-occur in a significant number. A mixed pair of Chiffchaff (male caucasicus and female abietinus) was also found here. The colour of the plumage of Chiffchaffs in Ciscaucasia varies more widely compared to allopatric populations. In many specimens bearing the abietinus haplotype in Ciscaucasia, the wing formula is identical to that typical for caucasicus and differs from that typical for abietinus in allopatric populations. The tret calls typical of caucasicus are included in the song of Chiffchaffs, which carry the abietinus haplotype and do not have notes characteristic of caucasicus in their song. Chiffchaffs from Ciscaucasia occupy an intermediate position between abietinus and caucasicus in the duration of individual song phrases and syllable time-frequency characteristics. During the captures, the males of caucasicus readily reacted to the broadcast of the abietinus song, and vice versa. Thus, all the results suggest hybridization between abietinus and caucasicus in Ciscaucasia.
Copyright (c) 2022 Irina Marova, Vladimir Ivanitskii, Irina Ilina, Anastasya Pecheneva, Pavel Kvartalnov, Yury Belocon, Maryana Belokon https://creativecommons.org/licenses/by/4.0
Conspecific density drives sex-specific spatial wintertime distribution and hoarding behaviour of an avian predator
Most studies on intraspecific competition, i.e., competition among individuals of the same species, have been conducted during the breeding season. Yet, at northern latitudes, intraspecific competition is expected to be particularly strong under the harsh weather conditions of the non-breeding season with limited number of resources available per individual. We studied the food-hoarding behaviour of wintering Eurasian Pygmy Owls (Glaucidium passerinum) along with sex- and age-specific spatial distribution in relation to fluctuating main prey abundance (voles) and conspecific density using a 15-year dataset. In low vole abundance years, increasing conspecific density reduced the total prey number stored by an owl, suggesting high costs of exploitative competition. The distance between the stores of nearest neighbours was greater when both were females, suggesting that the spatial avoidance is driven by sex-specific competition. However, food stores of females had a larger amount of prey items, especially when the nearest neighbour was of the same sex. The number of stores hoarded by an owl increased with increasing conspecific densities. Distributing the prey items to multiple store-sites instead of one (shifting from larder-hoarding towards scatter-hoarding) can help to reduce the overall loss to potential pilfering when conspecific density is high. These results combined suggest that high conspecific density inflames sex-specific interference competition, rather than solely exploitative competition, and in turn drives the observed sex-specific spatial distribution. Adopting a sex-specific spatial distribution according to hoarding and aggressive behaviour can be a way to reduce the severity of intraspecific competition locally and could have cascading effects on the prey community.
Copyright (c) 2022 Elina Koivisto, Giulia Masoero, Chiara Morosinotto, Eric Le Tortorec, Erkki Korpimäki https://creativecommons.org/licenses/by/4.0
Productivity of the Great Egret (Ardea alba) and Grey Heron (A. cinerea) in mixed heronries in Poland and behavioral response of fledglings to a drone
Productivity of avian populations provides important demographic information helpful in understanding population dynamics and processes involved during species expansions. We tested the hypothesis that the productivity of the two species of ecologically similar herons that breed together in mixed heronries is related to their expansion status. We expected the expansive species, colonizing the new area and increasing in numbers, to outperform the native species, whose abundance is stable. We studied the breeding success of two herons in mixed colonies in eastern Poland in 2018: Great Egret (Ardea alba) (an expansive species, increasing breeding range and population size), and the Grey Heron (Ardea cinerea) (a native species, stable breeding population). Mean productivity (number of young per nest) was similar for Great Egret and Grey Heron and appeared correlated to each other in mixed heronries. Productivity of both species was unrelated to the colony size, but Grey Heron tended to have higher productivity as the proportion of Great Egret nests in the colony increased. Similar productivity of both species can be explained by the sufficient food resources coupled with the low level of competition. The two species differed significantly in their response of young to the approaching drone: the mean probability of a young Great Egret adopting an upright display was 0.47 compared to only 0.18 in a young Grey Heron (P=0.025). This was unlikely an age-related difference as the fledglings of both species were at a similar stage of development, but may represent some kind of a species-specific trait. Our research once again shows that UAVs allow a quick and non-invasive study of the size of the breeding populations and reproductive performance of herons, egrets and other wading birds.
Copyright (c) 2022 Adam Zbyryt, Cezary Mitrus, Grzegorz Neubauer https://creativecommons.org/licenses/by/4.0
Facultative migration in two thrush species (Fieldfare and Redwing): Rowanberry abundance is more important than winter weather
Facultative migration is thought to be influenced by food and weather, with birds remaining in northern areas if food is abundant and weather conditions are benign, but migrating south when food is scarce and weather is harsh. However, the relative importance of these two factors has rarely been tested with long-term data, and effects of weather are poorly documented. Here, I assess whether winter numbers of the Fieldfare (Turdus pilaris) and the Redwing (T. iliacus) in southern Norway during the period 1980–2020 varied in relation to the abundance of an important source of winter food (rowanberries, Sorbus aucuparia) and indices of winter harshness (North Atlantic Oscillation index, temperature, duration of snow cover). Two regions with contrasting winter harshness (western Norway with a maritime climate, eastern Norway with a continental climate) were compared. Winter numbers of Fieldfare in both regions, and Redwing in eastern Norway, were highest in years with high rowanberry abundance. Weather had mixed influence on thrush winter numbers, but interacted with rowanberry abundance in several cases so that small numbers of thrushes occurred with the combination of low rowanberry abundance and harsh weather. Such interactions occurred both in eastern and western Norway, and for both species, including for the Redwing in western Norway. In conclusion, facultative migration was strongly related to food availability with large numbers wintering in years with large rowanberry crops, and with additional effects of harsh weather working in concert with low rowanberry abundance to reduce wintering numbers to low levels in some years.
Copyright (c) 2022 Svein Dale https://creativecommons.org/licenses/by/4.0
High adult survival in a northern Eurasian Curlew (Numenius arquata) population
Wetland birds such as waders are in decline across Europe. Information on demography is vital for assessing the causes of population declines, but estimates are needed from multiple populations and time periods. We used capture-recapture data from 2013–2022 including 134 individuals to estimate sex-specific apparent adult survival of Eurasian Curlews from a population breeding on agricultural fields in Finland, a stronghold region for this species in Europe. Using the Cormack–Jolly–Seber-model that considers the recapture probability of individuals, we estimated apparent survival of adults to be 0.89 (SE 0.03) for males and 0.92 (SE 0.03) for females. Our estimates of adult survival are slightly higher than those previously estimated from Fennoscandian breeding grounds in 1980s–1990s (0.82–0.88). Thus, our results suggest that adult survival of populations breeding in northern Europe has not declined during the last decades. Our study supports the view that changes in reproductive success is the main cause of decline in the Eurasian Curlew populations.
Copyright (c) 2022 Veli-Matti Pakanen, Reijo Kylmänen https://creativecommons.org/licenses/by/4.0
Consistent delay in recent timing of passerine autumn migration
Climate change affects important biological processes, bird migration phenology being a particular well-documented one. While spring migration have been found to advance by numerous studies, autumn migration is less studied and show more variable change in timing. Few studies of autumn migration are based on data from after 2000, leaving the last two decades to be relatively less studied. Here, we investigate recent change in autumn migration phenology of European passerines. The most recent available bird ringing data from Denmark is used to analyse phenological change of median and late migration of 14 passerine migrants between 2003–2021. We find an overall delay of autumn migration, mainly driven by short-distance migrants. All short-distance migrants, one out of five medium-distance and three out of five long-distance migrants delay autumn migration. None of the included species advance autumn migration significantly. As climate change has continuously resulted in milder conditions in north-western Europe, we expect this to cause further effects on migration phenology also in recent decades. Our results provide novel insight into recent migration phenology trends, and the observed delay in long-distance migrants may illustrate a changed response to climate change.
Copyright (c) 2022 Adam Søderdahl, Anders P. Tøttrup https://creativecommons.org/licenses/by/4.0
The effect of local weather conditions and nest box location on the reproduction of the Common Kestrel (Falco tinnunculus) in the farmland of eastern Poland
Artificial nests like nest boxes are commonly used to improve the reproductive output and population status of wild birds and advance our understanding of their evolutionary ecology. To investigate how the location of nest boxes and local weather conditions affect Common Kestrel reproduction (number of fledglings), 319 broods from 173 nest boxes in east-central Poland were examined. Of the six meteorological parameters analysed, only mean temperature and maximum temperature were selected as the best model. Mean daily temperature had a positive effect but maximum temperature a negative one on Common Kestrel reproduction. The first egg laying date was negatively correlated with the number of fledglings. Contrary to the assumption that trees should offer a superior microclimate in the canopy, nest boxes placed on utility poles have the same numbers of fledglings. The area of the main habitat type is not decisive in Common Kestrel productivity either. These findings may be helpful for ongoing conservation programmes and confirm that utility poles should be the preferred form of deployment of nest boxes as they are easier to monitor and maintain.
Nest box reuse in a migrating bird is independent of nest content
Site fidelity after successful nesting is an adaptation to spatially heterogeneous and temporally auto-correlated risk of nest predation. Cavity-nesting common goldeneye (Bucephala clangula) females use this strategy to minimize nest predation from pine marten (Martes martes), but because goldeneyes migrate they may save time when deciding where to nest by relying on information about successful nests gained in the previous year. I tested whether reuse of a nest box where the previous nest was successful is affected by the content. After a goldeneye had successfully nested, I manipulated nest box availability by offering two nest boxes; one in the original nest tree and one in a new tree for the season, each containing either old nest material from the successful nest or new nest material, i.e. wood shavings. The boxes were installed and relocated when goldeneyes were absent from the study area. The manipulation was designed to test whether goldeneyes reuse a cavity based on information conveyed by its current content, or on private or public information gained in the previous nesting season. Goldeneyes consistently reused the box in the original nest tree, independent of box content. Thus, when the information available in the current nesting season conflicted with information acquired in the previous nesting season, the goldeneyes relied on the latter rather than on information that would cost valuable time to update after arrival in spring. The common practice among ornithologists and land managers to clean nest boxes after each nesting would not affect cavity reuse in the goldeneye.
Habitat preferences of the Eurasian Griffon Vulture (Gyps fulvus) in Bulgaria to support species management
The Eurasian Griffon Vulture (Gyps fulvus) is a large scavenger with a population ranging between Portugal and India. The species is an obligate scavenger with a narrow ecological niche and is therefore particularly dependent on, and limited by habitat availability. The study aimed, for the first time in Eastern Europe, to identify the habitat preferences of the Griffon Vulture at landscape and cliff scales. We used long-term monitoring data between 1987–2018 to analyze habitat preferences of the natal Griffon Vulture population in the Eastern Rhodope Mountains, Bulgaria. We employed single explanatory variable tests to reveal the species habitat preferences at two spatial scales. The results revealed Griffon Vultures’ high preferences towards rocky habitats at the landscape level. At a cliff scale, the height and length of the cliff, the distance to the nearest conspecific colony and the distance to the nearest feeding site were the best predictors for the species habitat preferences. We stress the importance of these findings considering the current status of the species within the region. Our results are useful to support the future conservation of the Griffon Vulture population in Bulgaria and provide a starting point for future research in the Balkans and Eastern Europe.
Feeding conditions in breeding areas and selection of lekking sites by Great Snipe (Gallinago media) in Moscow Region, Russia