Movements of a male greater spotted eagle (Clanga clanga) during its 2nd and 3rd calendar years

The greater spotted eagle (Clanga clanga) is poorly known compared to other European eagles. We tracked an immature greater spotted eagle during 2018–2020 within the eastern European part of the species’ distribution, west of the Ural Mountains. Because so little is published about the annual movements of this species, especially from that region, tracking data from this single individual are valuable. 95% kernel density estimator (KDE) range sizes for the two complete winters in Yemen were 4,009 km2 (2018), 1,889 km2 (2019); 95% dynamic Brownian bridge movement models (dBBMM) encompassed 1,309 km2 (2018) and 1,517 km2 (2019). It returned to the same wintering area every year. During summer 2018, it settled into a small area (95% KDE = 126 km2; 95% dBBMM = 21 km2) near Birsk, eastern European Russia; in 2019 it wandered over a huge area (95% dBBMM = 66,304 km2) of western Kazakhstan and southern Russia, south west of Yekaterinburg. Spring migration 2018 was west of the Caspian Sea; during 2019 it was east of it. Mean speed of spring migration was 160±120 km/day during 2018, and 132±109 km/day during 2019. Autumn migration passed east of the Caspian in both years, and the mean speed of migration was 62 ± 78 km/day in 2018, and 84 ± 95 km/day in 2019. During both spring and autumn migrations, the eagle made stopovers, mostly lasting 1–2 days. The eastern Alborz Mountains in northeastern Iran appeared to be an important stopover locale, where autumn stopovers lasted 19 days (2018) and 27 days (2019). These and other data suggest that most greater spotted eagles that spend summers west of about 42°E, winter in southern Europe, Asian Turkey, the Levant and Africa, and those that summer to the east of that meridian winter in southern Asia, including Arabia.

Comparison of orbital asymmetries among some raptor species: “when size does not matter”

A sample of 73 dry, well-preserved skulls was studied, representing various species of raptors with different foraging strategies. The sample included Accipiter nisus (n = 15), Buteo buteo (n = 13), Gyps fulvus (n = 24) and Neophron percnopterus (n = 5), Bubo bubo (n = 16) and Tyto alba (n = 2). Geometric morphometric methods were used to detect orbital asymmetries. On digital pictures of each skull side, a set of 16 semi-landmarks and two landmarks were located in order to describe the orbital ring. The variables were analysed based on Generalized Procrustes analysis. The morphometric data showed that the orbital asymmetry of raptors differed significatively between species, although directional asymmetry (e.g. left orbita systematically more developed than the right) appeared not to be correlated with orbital size. This indicates that larger orbitas do not lead to greater asymmetry. Differences between species should rather be explained by their foraging strategies and degree of visual obstruction in their natural environment.

Changes in the Eurasian eagle-owl (Bubo bubo) population in Czechia and their association with legal protection

The article deals with trends in the Eurasian eagle-owl (Bubo bubo) population in Czechia and the interplay between legal regulation of hunting and nature protection. In the early 20th century, the eagle-owl population in Bohemia decreased to an estimated 20 nesting pairs, and the population in Moravia and Silesia was subsequently estimated to be similarly low. In previous centuries, eagle-owls had been persecuted as pest animals; additionally, their chicks were picked from nests to be kept by hunters for the eagle-owl lure hunting method (“výrovka” in Czech), where they were used as live bait to attract corvids and birds of prey, which were subsequently killed by shooting. As soon as the state of the eagle-owl population was established in the 1900s, the effort to save the autochthonous eagle-owl population commenced. Nevertheless, when eagle-owls became legally protected from killing in the 1930s, the eagle-owl lure hunting method was not prohibited. The intensified use of this hunting method in the 1950s was accompanied by serious decline in the populations of birds of prey in the Czech countryside, when tens of thousands of Eurasian sparrowhawks (Accipiter nisus), northern goshawks (Accipiter gentilis), common buzzards (Buteo buteo) and rough-legged buzzards (B. lagopus) were killed on a yearly basis. The usage of eagle-owl chicks in lure hunting was criticised by ornithologists concerned with the conservation of birds of prey. The eagle-owl thus became a subject of more general debate on the role of predators in nature, and this debate (albeit regarding other predator species) has continued to the present-day. As the eagle-owl population has been growing steadily following the prohibition of its killing in the 1930s, its story may serve as an example of the need for effective legal protection of predators to ensure their survival in the intensively exploited central-European environment. The article examines the successful preserving of the eagle-owl in the Czech countryside, from its low point in the early 20th century towards today’s stable and ever-increasing population, focusing on environmental, conservationist, legal and societal aspects of the issue.

Age of maturity and exceptionally distant natal dispersal of over 500 km by a male lesser spotted eagle Clanga pomarina

According to previous studies using colour rings, lesser spotted eagles Clanga pomarina have established breeding territories up to 249 km from their natal site. A colour-ringed lesser spotted eagle nestling from NE Poland settled 540 km further west in NE Germany. This male was discovered at the age of six and nested there for several years. This finding is all the more remarkable because the bird was a male, which in large eagles typically settle nearer to their natal sites than females. They apparently reproduce successfully for the first time later than females, normally at the age of five.

Summary of raptor and owl ringing in Slovakia in the period from 2012 to 2019

Between 2012 and 2019, 6523 raptors and owls (30 species) were ringed in Slovakia. The most abundant was the common kestrel (2811 individuals), then the western marsh harrier (664) and saker falcon (517). The proportion of nestlings among all the ringed individuals was 84.4%. In the given period, 340 recoveries of raptors and owls (23 species) were recorded in the ringing station database. This number included 160 recoveries of individuals colour-marked and also recovered in our territory. There were 83 recoveries of birds ringed in Slovakia and resighted abroad. The last 97 recoveries were of individuals ringed abroad and recovered in Slovakia. In summary, most of the recoveries (of all types) were of Eastern imperial eagle (62 recoveries), then red-footed falcon (51) and common kestrel (43). Most of the recovery circumstances were ring reading (44% in total), recaptures (15%) and findings of bird cadavers. Regarding raptors or owls, collisions with vehicles (5%) and electrocutions (5%) were frequent causes of their deaths.

Diet of the lesser kestrel Falco naumanni at post-breeding roosts in southern Albania

The lesser kestrel is an insectivorous and migratory falcon species, frequently using communal roosts in the post-breeding period in southern Europe. Using pellet analysis from two post-breeding roosting sites in southern Albania collected in August 2017, we identified 1539 prey items belonging to approximately 58 prey species, 20 families and 7 orders in 110 pellets from two sites. Invertebrates made up the major part of the diet spectrum (PNI = 99.8 %, PFI = 100 %). Invertebrate prey body size varied between 8 and 62 mm (mean 28.1 mm). Bush-crickets (Tettigoniidae) and locusts (Acrididae) were the most abundant and frequent prey groups (PNI = 33 % resp. 48.6 % and PFI = 97 % resp. 94 %). Within the bush-cricket family we could identify the species of genera Tettigonia, Decticus, Platycleis, Isophya and Metrioptera. The species of genera Calliptamus, Stenobothrus and Locusta belonged among the locust species identified in the food. Birds and mammals were found in pellets only occasionally. The prey composition was rather similar at both studied sites, while locusts (Acrididae) were more abundant at the Jorgucat site and bush-crickets (Tettigonioidea) at the Mollas site in the same time. Prey groups Scarabeidae beetles and other beetles (Coleoptera other) were more abundant and frequent at Mollas than at Jorgucat, and spiders were more frequent at Jorgucat. These results suggest that the high abundance of orthopterans and beetles in the food supply in certain localities is the main reason for selection and stable occupancy of these massive communal roosting sites by lesser kestrels in Albania.

Spatial distribution of four sympatric owl species in Carpathian montane forests

Knowledge about spatial distribution of owl species is important for inferring species coexistence mechanisms. In the present study, we explore spatial patterns of distribution and habitat selection of four owl species – Eurasian pygmy owl (Glaucidium passerinum), boreal owl (Aegolius funereus), tawny owl (Strix aluco) and Ural owl (Strix uralensis) – ranging in body mass from 50 g to 1300 g, with sympatric occurrence in temperate continuous montane forests in the Veľká Fatra Mts., Western Carpathians, central Slovakia. Locations of hooting owl males were surveyed between 2009–2015 in an area of 317 km2. Spatial point pattern analysis was used for analysis of owl distribution. Random patterns of owls’ spatial arrangement dominate at both intra‐ and interspecific levels within the studied area. Only intraspecific distribution of pygmy owls and interspecific distribution of Ural owls toward tawny owls exhibited positive associations. This discrepancy with other studies can be explained in terms of pygmy owls’ preference for high‐quality nest sites and/or spatial clustering in their prey distribution, and due to aggressive behaviour of dominant Ural owls toward subdominant tawny owls, respectively. Moreover, we found considerable overlap in habitat preferences between owl species, considering stand age, stand height, tree species richness, distance to open area, elevation, slope, percentage of coniferous tree species and position on hillslope, although pygmy owls were not registered in pure broadleaved stands, Ural owls were not registered in pure coniferous stands, and boreal and Ural owls were more common on slope summits and shoulders than tawny and pygmy owls. The observed patterns of spatial arrangement might suggest developed coexistence mechanisms in these owl species; differences between studies may indicate complex interactions between intra‐ and interspecific associations and habitat quality and quantity, food availability and owl species involved in those interactions on a landscape scale.

The identity of Azara’s description No. 18 “Gavilán mixto pintado” is a juvenile Harris’s hawk (Parabuteo unicinctus)

The classic ornithological work by Félix de Azara “Apuntamientos para la historia natural de los páxaros del Paraguay y Rio de la Plata” was one of the first descriptive texts dealing with the avifauna of the Southern Cone of South America. Azara’s No. 18 “Gavilán mixto pintado” has long been misidentified as a juvenile great black hawk (Buteogallus urubitinga ((Gmelin, 1788)). However, there are clear inconsistencies in the description of the plumage coloration, shape and measurements which make that identification erroneous, and Azara’s No. 18 can in fact be convincingly identified as the juvenile plumage of the Harris’s hawk (Parabuteo unicinctus (Temminck, 1824)). The description by Azara contains numerous diagnostic characteristics for that species, and the measurements provided by him are inconsistent with those of the great black hawk, yet remarkably similar to those provided by the same author for the description of the adult No. 19 “Gavilán mixto obscuro y canela”. No scientific names have apparently ever been based on Azara No. 18.

Bird mortality on medium-voltage power lines in the Czech Republic

In 2015–2016, 6,429 km medium-voltage power lines with 76,430 pylons were checked for bird mortality in the Czech Republic. 1,326 bird victims of power lines were found, 156 of which died after collisions, and 1,170 birds were electrocuted. They belonged to 60 species from 12 orders, and birds of prey made up almost half of all victims. Steel pylons bearing several cross-arms including upper and crosswise jumpers were identified as most dangerous from the electrocution point of view. On the other hand, pylons in straight lines with Pařát cross-arms (triangular arrangement of conductors without any horizontal bar) were among the least dangerous, and when they had a simple perch fitted below the cross-arm, no mortality was recorded. But these pylons are new in practice and despite becoming widely used recently, they form less than one tenth of all pylons in the Czech Republic. On other pylons various types of mitigation measures have been installed. Commonly used plastic covers and plastic strips have proved to be especially effective, but only in cases when they are undamaged and correctly installed.

Riding the storm out: select demographics of a breeding population of Cooper’s hawks (Accipiter cooperii) following a severe spring snowstorm

The demographic responses to severe weather by top-level predators, including birds of prey, are underreported and/or unknown. Severe storms are predicted by climate change models to increase globally and in frequency into the 22nd century. In April 2018, a population of breeding Cooper’s hawks (Accipiter cooperii) in central Wisconsin, USA, experienced three days of heavy snowfall in the most severe storm, in pre-incubation-stage, for 39 years (1980–2018). Here I report select demographic outcomes of this nesting population following this intense weather. The median hatching date of 10 June in 2018 was the sixth latest such metric in those 39 years (and the latest in 22 years since 1996) for this population, which has advanced its breeding schedule about 1.3 days/decade due to climate change or warming. Survival of a total of 16 color-marked breeding adults, 15 males and 1 female, observed pre-storm in the nesting areas, was 100% up through the late nestling stage in the same nesting areas where these birds were initially detected in 2018. Average clutch size (4.4 eggs/nest) and average brood size (4.0 young/nest) were similar to the overall average annual metrics of these demographics for this population in the earlier 38 study years. Nest success, whereby 95% of 21 nests with eggs produced advanced-aged young, was higher in 2018 than the overall average of 77% nest success rate during the earlier years. The later timing of hatching in 2018, likely due to the severe spring snowstorm, appeared to have no deleterious effects either on survival of the breeding adults or on the reproductive output of this healthy study population. Tree-canopy prey may have served as important alternative food for this typically ground-foraging raptor in 2018.