Red-backed Shrike Lanius Collurio Research Articles

Effect of Management of Grassland on Prey Availability and Physiological Condition of Nestling of Red-Backed Shrike Lanius collurio.

The study aimed to determine the influence of grassland management on the potential food base of the red-backed shrike Lanius collurio and the condition of chicks in the population inhabiting semi-natural grasslands in the Narew floodplain. The grassland area was divided into three groups: extensively used meadows, intensively used meadows fertilised with mineral fertilisers, and intensively used meadows fertilised with liquid manure, and selected environmental factors that may influence food availability were determined. Using Barber traps, 1825 samples containing 53,739 arthropods were collected, and the diversity, abundance, and proportion of large arthropods in the samples were analysed depending on the grassland use type. In the bird population, the condition of the chicks was characterised by the BCI (Body Condition Index) and haematological parameters (glucose level, haemoglobin level, haematocrit, and H:L ratio). The diversity of arthropods was highest in extensively used meadows. Still, the mean abundance and proportion of arthropods over 1 cm in length differed significantly for Orthoptera, Hymenoptera, Arachne, and Carabidae between grassland use types, with the highest proportion of large arthropods and the highest abundance recorded in manure-fertilised meadows. The highest Body Condition Indexes and blood glucose levels of nestlings indicating good nestling nutrition were recorded in nests of birds associated with extensive land use. The H:L ratio as an indicator of the physiological condition of nestlings was high on manure-fertilised and extensively managed meadows, indicating stress factors associated with these environments. This suggests that consideration should be given to the effects of chemicals, such as pesticides or drug residues, that may come from slurry poured onto fields on the fitness of red-backed shrike chicks.

Brain size mediates the choice of breeding strategy in the red-backed shrike Lanius collurio.

The brain size of vertebrates represents a trade-off between natural selection for enhanced cognitive abilities and the energetic constraints of brain tissue production. Processing information efficiently can confer benefits, but it also entails time costs. Breeding strategies, encompassing timing of breeding onset and nest-site selection, may be related to brain size. In this study, we aim to elucidate the relationship between brain size, breeding timing, nest-site choice, and breeding success in the red-backed shrike Lanius collurio. Our findings revealed that the timing of the first egg-laying date was associated with female head size, with larger-headed females tending to lay eggs later in the breeding season. Additionally, we observed that breeding success was positively correlated with increased nest concealment. However, this relationship was stronger in males with smaller heads. In turn, nest concealment was not related to head size but primarily influenced breeding onset. These results suggest that the choice of breeding strategy may be moderated by brain size, with differences between sexes. Larger-headed females may invest more time in selecting nesting sites, leading to delayed breeding onset, while larger-headed males may compensate for suboptimal nest concealment. Our study sheds light on the intricate interplay between brain size, breeding timing, nest-site preferences, and breeding success in passerine birds, underscoring the potential role of cognitive capacity in shaping individual decision-making processes.

Do cuckoo calls affects red-backed shrike settlement pattern? An experimental approach

Birds select breeding territories by assessing territory quality and considering predation pressure. However, in many small passerines, brood parasitism may also play an important role in territory occupancy. Settlement decisions are made under time pressure, especially for late migrants. An example of late migrants is the red-backed shrike Lanius collurio, a species wintering in sub-tropical Africa, which serves as a host for the common cuckoo Cuculus canorus and arrives in territories a few days later than their brood parasite. We expected that arriving red-backed shrikes avoided territories with common cuckoo presence. Then, we tested how experimentally provided artificial playback calls of the common cuckoo and woodpigeon (treated as control) affected the probability of red-backed shrike settlement. In the breeding season 2021, we observed 279 red-backed shrike territories to assess the effect of playback of common cuckoo calls on their host presence. Moreover, we adopt information on shrike territories collected in previous years to establish territory quality, measured by occupancy pattern over years. Each of these places was also checked for the presence of corvids, which are predators of shrike nests. We did not find difference with lower preference of shrikes towards cuckoo calls and to pigeon calls Columba columbus, what suggest the human presence and manipulation in the territories during experiments with recorders should be incorporated as an important factor to understanding shrikes’ settlement behaviour. What is interesting we found no negative effect of corvids (jay Garrulus glandarius) in control territories. However, shrike territories where cuckoo calls were emitted and where the presence of corvids was found were less likely to be inhabited by shrikes. Therefore, territory quality, human presence enhanced by nest predators, is an important factor affecting host–parasite interactions.

Breeding success of passerine birds in the forest steppe of European Russia

In the period from 1985 to 2023, the breeding success of 15 bird species was studied in the Voronezh Nature Reserve (50°21ʹ-52°02ʹ N, 39°21ʹ-39°47ʹ E), where there has been no economic activity for 100 years. The plant cover consists of pine (32.3% of the total area), oak (29.3%), aspen (19.3%), birch (5.7%) and alder (5.2%) forests. 2004 nests were monitored. Low breeding success (25.4-27.9%, determined by the modified Mayfield method) was found in the Blackbird Turdus merula , the Song Thrush T. philomelos , the Finch Fringilla coelebs and the Greenfinch Chloris chloris. From 1.6 to 1.8 fledglings fly out for one breeding attempt. The average level of breeding success (38.7-50.4%) was found in the Common Chiffchaff Phylloscopus collybita , the Red-backed Shrike Lanius collurio , Redwing Turdus iliacus , Eurasian Blackcap Sylvia atricapilla , Garden Warbler S. borin and Hawfinch Coccothraustes coccothraustes . From 2.1 to3.4 fledglings fly out for one breeding attempt. A high level of breeding success (60.6-82.5%) was found in the Great Tit Parus major , the Common Redstart Phoenicurus phoenicurus , the Pied Flycatcher Ficedula hypoleuca , the Collared Flycatcher F. albicollis and the Spotted Flycatcher Muscicapa striata . From 3.7 to 7 fledglings fly out for one breeding attempt. Due to the increased pressure of nest predators, the breeding success of birds in the Voronezh Nature Reserve is often lower than in other areas. The greatest breeding success is typical for birds that place nests in hollows and other shelters. Breeding success is significantly lower in openly nesting species, especially in birds that begin nesting before the leaves bloom on trees and shrubs.

Brood survival in the Red-backed Shrike Lanius collurio in eastern Poland

Brood survival as an expression of breeding success is a component of bird fitness and the principal parameter underlying bird population dynamics. The main factor limiting brood survival is predation pressure, and birds have developed anti-predator strategies by selecting safer places for building nests and breeding. Here, we examined whether nest location affected the level of predation pressure. To do so, we analyzed brood survival in a Red-backed Shrike (RBS) Lanius collurio population breeding in the low-intensive agricultural landscape of eastern Poland. The mean survival probability for the whole nesting period was 0.540 and was higher for the incubation period (0.787) than for the nestling period (0.696). Cox’s proportional hazard model did not show any significant traits describing the location of the nesting shrub or the nest’s position in the shrub that could have affected RBS brood survival. We consider the composition of the local predator community to influence brood survival more than the location of a nest in the bush. The Eurasian Magpie Pica pica is mainly responsible for RBS brood predation. Red-backed Shrikes do not defend their broods against Magpies using acoustic signals and direct contact. Since Magpies search the bushes thoroughly, the shrikes’ nest concealment strategies are ineffective in the face of this predator.

When Toxicity is Not Enough: Review and New Data on Blister Beetle (Coleoptera, Meloidae) Predation by Shrikes

Shrikes from the genus Lanius are generalists in terms of diet, even consuming highly toxic species, as blister beetles (Coleoptera, Meloidae). Despite the fact that regular predation on these coleopterans have never been described both in recent and historical literature, birds stand out as one of the groups to most often prey upon these insects. In the Old World, records of shrikes preying on oil-beetles — most of them treated as anecdotal — have been published since the 19th century. However, despite being repetitive, no review or in-depth study of this behavior has been conducted. After a literature study and new data collected in the Iberian Peninsula, it seems an extended behaviour within the clade. As could be observed in a high number of cases, birds even apply a specific technique, selecting specific body parts to kill the beetle, more sclerotic and presumably less toxic. In some cases, strict predation has been demonstrated. To date, at least six different shrike species — Red-backed Shrike Lanius collurio, Great Grey Shrike L. excubitor, Iberian Grey Shrike L. meridionalis, Loggerhead Shrike L. ludovicianus, Lesser Grey Shrike L. minor, and Woodchat Shrike L. senator — have been found to show signs of preying on at least nine Meloidae species throughout Europe, North Africa and North America, constituting a line of research that should be studied in greater detail.

Delayed egg-laying in Red-backed Shrike Lanius collurio in relation to increased rainfall in east-central Poland

Climate change has affected the breeding parameters of many animal species. In birds, most studies have focused on the effects of temperature on clutch phenology and clutch size. The long-term influence of other weather factors, including rainfall, on breeding parameters have been analysed much less often. Based on a 23-year dataset and 308 broods, we documented shifts in the timing of breeding, clutch size and mean egg volume in a long-distance migrant, the Red-backed Shrike Lanius collurio, from a central European population. We found a 5-day shift towards delayed breeding, but no differences in brood size or egg volume during those 23 years. The GLM analysis showed that the mean May temperature had a positive influence on the clutch initiation date, whereas the number of days with rain delayed laying. During the period 1999–2021, there was no change in the mean May temperature, but total precipitation and the number of days with rain in May increased. Thus, delayed nesting in this population was probably due to the increase in rainfall during this period. Our results provide a rare example of delayed nesting in birds in recent years. Predicted changes in the climate make it difficult to assess the long-term impact of global warming on the viability of Red-backed Shrike populations in east-central Poland.

Activity patterns throughout the annual cycle in a long-distance migratory songbird, the red-backed shrike Lanius collurio

BackgroundLong-distance migratory birds undergo complex annual cycles during which they must adjust their behaviour according to the needs and conditions encountered throughout the year. Yet, variation in activity throughout the entire annual cycle has rarely been studied in wild migratory birds.MethodsWe used multisensor data loggers to evaluate the patterns of activity throughout the complete annual cycle of a long-distance migratory bird, the red-backed shrike Lanius collurio. Accelerometer data was used to identify life-history stages and to estimate levels of activity during various phases of the annual cycle. In this study, we analysed the variation in daytime activity along the annual cycle and between migratory and non-migratory days.ResultsThe birds’ daytime activity varied throughout the annual cycle while night-time activity was almost exclusively restricted to migratory flights. The highest daytime activity levels were observed during the breeding season, while it remained low during autumn migration and the winter period. Daytime activity differed between sexes during the breeding period, when the males showed the highest level in activity. During migratory periods, both sexes exhibited a higher daytime activity in spring compared to autumn migration, being particularly high in the final migratory leg towards the breeding ground. The birds showed a lower daytime activity on migratory days (days when a migratory flight took place during the succeeding night) than on non-migratory days during both migratory seasons.ConclusionsActivity measured during daytime results from a combination of several behaviours, and a high daytime activity during spring migration and the breeding period is possibly reflecting particularly energy-demanding periods in the annual cycle of migratory birds. The use of multisensor data loggers to track annual activity provides us with a full annual perspective on variation in activity in long-distance migratory species, an essential approach for understanding possible critical life-history stages and migration ecology.

Influence of researcher experience and fieldwork intensity on the probability of brood losses in sensitive species: The case of the Red-backed Shrike Lanius collurio

Minimizing disturbance to animals when studying them should be a major consideration in ecological research design, especially when species are known to be sensitive to disturbances. A basic method in the study of bird reproductive ecology involves nest visits, but these can adversely affect birds’ breeding success. Appropriate fieldwork procedures are therefore highly important, especially in the case of timid and sensitive species. This study aimed to assess the impact of the method of searching for nests of Red-backed Shrike Lanius collurio on the probability of these birds abandoning their broods. Our study revealed that observer experience and nest searching intensity did influence the likelihood of brood desertion by this species. Less field experience and a greater nest searching intensity caused the shrikes to abandon their nests more often. We recommend paying scrupulous attention to the behaviour of the birds when searching for nests and when looking for nests after incubation has started.

Red-Backed Shrike Lanius collurio Whole-Genome Sequencing Reveals Population Genetic Admixture

The Red-backed Shrike (Lanius collurio) is a medium-sized, carnivorous passerine, occurring throughout the western Palearctic. As with numerous other bird species, its numbers are declining, mainly due to anthropogenic factors. Therefore, revealing the population structure and genetic diversity is paramount in ensuring the survival of the species. However, until present, only mitochondrial DNA has been targeted to reveal the genetic structure of the species. These studies suggested a panmictic population structure. In this study, we employed next-generation sequencing of 88 Red-backed Shrikes from 11 countries and used single nucleotide polymorphisms (SNPs)) to investigate the population structure. Even with such high-resolution DNA data, we found considerable genetic variability, but our results indicate no genetic structure in the Red-backed Shrike, suggesting a panmictic population. Migrant birds from Israel and Kuwait could not be attributed to breeding populations. Panmixia is the genetic legacy of the widespread and continuous distribution of the species, high locomotion capacities, and, most importantly, the numerous ice ages from the past few million years, which forced various populations to retract to refugia and expand their ranges several times, and to interbreed both in the glacial refugia and during warm periods in Eurasia.

Eggshell Patterning in the Red-Backed Shrike Lanius collurio: Relation to Egg Size and Potential Function

Despite numerous studies on avian eggs, the function of eggshell patterning remains largely unknown. Using a museum collection of Red-backed Shrike clutches, we estimated the repeatability of characteristics describing the intensity and contrast of egg pigmentation, as well as egg size and shape. Digitalized photographs of eggs were used for all measurements. Repeatability was highest for overall pigmentation intensity and overall pigmentation contrast (R = 0.81 and R = 0.82 respectively). Lower values were recorded for egg breadth (R = 0.66) and shape (R = 0.57). These findings suggest that eggshell patterning, as well as the variables describing egg size and shape, may respond to natural selection. Among the possible functions of this trait, condition signalling within species and mimicry are the most probable. To obtain more evidence of this, however, further studies in wild populations are required.

Grassland bird species in mountain pastures Zaprikraj and Zapleč in the southern Julian Alps, Slovenia

AbstractGrassland birds were surveyed in two mountain pastures (Zaprikraj and Zapleč) in the southern part of the Julian Alps, Slovenia. The survey was carried out during the mornings between 26 and 30 June 2005. Due to the incomplete survey (only one visit, no nocturnal or targeted surveys and late season survey), the surveyed birds’ breeding density is only a rough estimate. 167 pairs belonging to 12 species were counted, with Tree (average density of 1.64 p/10 ha) and Water Pipit (average density of 1.60 p / 10 ha) being the most abundant. Both were observed in all altitudinal belts. The highest density in individual altitudinal belt was calculated for Red-backed ShrikeLanius collurio(3.78 p/10 ha) and Water Pipit (3.61 p/10 ha). In well preserved grasslands in the study area, most species reached high breeding densities compared to other parts of Slovenia and all were recorded higher than during the 1992 survey, although still mostly within limits of the elevations elsewhere in Slovenia. Breeding density of SkylarkAlauda arvensisdecreased with the elevation. WhinchatSaxicola rubetra, Skylark and Red-backed Shrike used significantly gentler slopes, while Pipits showed no preference for particular slopes.

Foraging behaviour and diet in two sympatric shrike species during autumn migration across the Arabian Peninsula.

In situations of restricted food supply, the trophic niches of closely-related species of animals should be separate. For sit-and-wait hunters, such as shrikes, this is associated with competition for food and hunting sites. In the present study, the foraging behaviour of two shrike species – Red-tailed Shrike Lanius phoenicuroides and Red-backed Shrike Lanius collurio – was studied in a desert habitat in Oman. The fieldwork was carried out in September 2019, during the peak migration of these birds. Their behaviour was recorded in detail during 30-minute observation bouts. A General Linear Mixed Model with logit link function and binomial error variance was used to compare their behaviour. The type of perch and its height did not differ between them, but there were significant differences in their use of look-out posts only in the mean duration of a single perching event, which was more than twice as long in Red-backed Shrike. No differences in prey size were found between the species and hunting success (the ratio of successful attacks to all attacks) was similar in both (RtS-RbS: 46 vs. 61%). Dietary diversity was twice as great in Red-tailed Shrike as in Red-backed Shrike, but in general, their diets did not differ very much. Dietary overlap between the species at this level of prey identification was 92%. This absence of differences in some aspects of behaviour and diet may be due to the similarity of the two species, above all their same body size, and even the possibility of hybridization. If the species compared are so similar due to body size, behaviour and evolutionary relationship their food niches may overlap.

The function of food storing in shrikes: the importance of larders for the condition of females and during inclement weather

Food storing is a well-known phenomenon among birds, described in shrikes Laniidae. The preferred explanation suggests that its function is to signify male quality to females and to mark territorial borders during the mating period. The importance of food storing must vary among different species, however, because in the Red-backed Shrike Lanius collurio, this behaviour takes place during the nestling care period. The aim of this study was to evaluate the significance of food storing by male Red-backed Shrikes. We did not find any differences in the breeding parameters between pairs in which the males did or did not store food. There was, however, a significant tendency for the number of stored prey items to increase when the atmospheric pressure was falling prior to the onset of rain. The mates of males that did store food had a larger body mass than those females whose partners did not do so. This study showed that food storage have a variety of functions, including different ones compared with those described for the best-known shrike species. Differences in food storing phenology in various shrike species are probably due to the period when they start nesting: Red-backed Shrikes start their breeding season in late spring, when food is plentiful. Our study demonstrates that the abundance of food in territories and one’s own condition, as expressed by the number of prey items stored when food is readily available, is not really so relevant. The food store of a Red-backed Shrike thus functions as a larder, which the female makes use of when her energy requirements are the highest, i.e. when caring for her young. Larders are thus essential if females are to remain in good bodily condition: this could be significant if a clutch is lost and a replacement one has to be laid.

High Genetic Diversity among Breeding Red-Backed Shrikes Lanius collurio in the Western Palearctic

Revealing the genetic population structure in abundant avian species is crucial for understanding speciation, conservation, and evolutionary history. The Red-backed Shrike Lanius collurio, an iconic songbird renowned for impaling its prey, is widely distributed as a breeder across much of Europe, Asia Minor and western Asia. However, in recent decades, many populations have declined significantly, as a result of habitat loss, hunting along migration routes, decrease of arthropod food, and climate change e.g., severe droughts in Africa. Within this context, gene flow among different breeding populations becomes critical to ensure the survival of the species, but we still lack an overview on the genetic diversity of the species. In this paper, we analyzed the mitochondrial cytochrome b gene (mtDNA) and the cytochrome c oxidase subunit 1 gene (mtDNA) of 132 breeding Red-backed Shrikes from across the entire breeding range to address this knowledge gap. Our results revealed consistent genetic diversity and 76 haplotypes among the Eurasian populations. Birds are clustered in two major groups, with no clear geographical separation, as a direct consequence of Pleistocene glaciations and apparent lineage mixing in refugia. This has led to genetic panmixia.

Annual GPS tracking reveals unexpected wintering area in a long-distance migratory songbird

Recent technological development has made it possible to pinpoint precise locations of small migratory songbirds throughout their annual cycle, providing the opportunity for improving our understanding of year-round habitat use. Here, we use GPS loggers to map the exact location and habitat use at stationary sites throughout the annual cycle of a long-distance migratory songbird, the Red-backed Shrike Lanius collurio. Although the main staging sites confirmed previous findings from light-level geolocation studies, one individual wintered in south-western Chad, an area with only a few historical records of this species. This study highlights opportunities for answering new questions and gaining more knowledge using fine-scale tracking of migratory songbirds.

Comparative foraging behaviour of three species of shrike in southern Africa

Utilisation of food resources in migrant and resident birds living sympatrically often leads to differences in feeding strategy. For sit-and-wait hunters such as shrikes, it is connected with competition for food and hunting places. In this study, foraging behaviour of three shrike species was studied in savanna-like habitat in southern Africa. The fieldwork was carried out in December 2017 during wintering season of Lesser Grey Shrike Lanius minor and Red-backed Shrike Lanius collurio and breeding season of Common Fiscal Lanius collaris. Details of the bird's behaviour were recorded during 30 min observations of each bird. A general linear mixed model with logit link function and binomial error variance was used to compare the species’ behaviour. Although the type of perch-site and perching time did not differ between species, Red-backed Shrike used places situated significantly lower than other shrikes. This species also more often used bushes and attacked from lower perch-sites than Lesser Grey Shrike. This may possibly be due to interspecific competition and antipredator behaviour of Red-backed Shrike. No differences in foraging behaviour between Common Fiscal and Lesser Grey Shrike were observed. All three species utilised the same category of prey. Hunting success (the ratio of successful to all attacks) was low and similar in all three species (47%–57%). The lack of statistically significant differences in behaviour, hunting success and size of prey items among shrike species may be a consequence of the relatively short observation time and small sample sizes.

Full-year tracking suggests endogenous control of migration timing in a long-distance migratory songbird

Following ongoing technological advances, an increasing amount of full-year tracking data on individual migratory movements is becoming available. This opens up the opportunity to study how migration develops within individuals in consecutive years and the extent to which the migratory program is constrained. Such knowledge is essential for understanding the degree of individual flexibility during the annual cycle, which may help identifying potential bottlenecks, where the range of individual decisions is restricted. In this study, we investigate repeatability in time of a long-distance migratory songbird, the red-backed shrike Lanius collurio, tracked across consecutive years (n = 7). Furthermore, we explore the population variability and dependencies between consecutive events of departure and arrival throughout the annual cycle in this species (n = 15). We find that individuals show high repeatability in timing of departure from their two main non-breeding areas in sub-Saharan Africa. In contrast, low repeatability is found in timing of arrivals to stationary sites throughout the annual cycle. Population variation in timing of departure and arrival was similar across all events, ranging from 30 to 41 days, and was highly dependent on timing of preceding events. We conclude that timing of departures is the key event potentially controlled by the individual innate migration program, while arrivals are more flexible, likely dependent on the environmental conditions experienced en route in red-backed shrikes. Still, apparent flexibility in the individual schedule may be hampered by overall constraints of the annual cycle. The annual migration schedule of migratory animals is controlled by a combination of endogenous and exogenous factors. Understanding the temporal dynamics within and between individuals across the annual cycle is important to assess to which extent the migratory schedule is constrained in time. By using full-annual cycle tracking data of individual red-backed shrikes tracked across consecutive years, we find that individuals are highly consistent in their decision to depart from their main non-breeding areas in sub-Saharan Africa, whereas arrivals are less consistent throughout the annual cycle. Overall, the migration schedule is highly constrained across the annual cycle, with each arrival and departure event being dependent on the previous event. Our results suggest that departure decision is underlying endogenous control and that little flexibility is available throughout this complex migration system.

Habitat preferences of Red-backed Shrikes Lanius collurio and Barred Warblers Sylvia nisoria breeding sympatrically in a wetland/farmland mosaic

ABSTRACTCapsule: The Red-backed Shrike Lanius collurio and the Barred Warbler Sylvia nisoria had similar habitat preferences and their territories often overlapped. However, we found that Red-backed Shrikes were more flexible in habitat choice whilst Barred Warblers had more specific requirements.Aim: We aimed to analyse and compare distribution and habitat preferences of Red-backed Shrikes and Barred Warblers breeding sympatrically in semi-natural landscape in a wetland/farmland mosaic.Methods: We examined habitat availability and use by the two species within their breeding territories to identify differences in habitat selection.Results: Territories of both species were similar in habitat composition and used levees, bushes, fallow areas and single trees. However, the spatial characteristics of the territories differed between species. Red-backed Shrikes used a wider range of sizes and shapes of habitat patches, whilst Barred Warblers preferred a more complex landscape structure and a higher diversity of habitat types. We also found that areas of 71% of Barred Warbler and 34% of Red-backed Shrike territories overlapped.Conclusion: Whilst both species showed similar habitat choices, they appeared to differ significantly in terms of landscape structure: Red-backed Shrikes were more flexible and less selective than Barred Warblers in their habitat choice.

Distribution of the Red-Backed Shrike Lanius Collurio at Its Western Range Boundary: Patterns and Conservation Prospects

This note examines the effects of habitat, landscape, climate and geographical situation on the occurrence probability of the Red-backed Shrike at its westernmost range boundary. The results from 127 sampling localities distributed east-to-west along 600 km in northern Spain reflect local and regional effects on species distribution. Habitat patch size (the species prefers large patches) and summer temperatures (the species avoids warmer sites) are the two main environmental correlates of species distribution. In addition, the occurrence of the Red-backed Shrike decreased in the westernmost sectors of the study area. This result could be related to a peninsula effect potentially reinforced by the atypical migratory circuit of this summer passerine (birds arrive from the east). The conservation prospects of this peripheral population suggest a retreat to cold highlands as global warming increases, a reduction in suitable habitat patches due to forest encroachment resulting from rural abandonment and the reduced availability of individuals to offset local extinctions in the westernmost border of its European range. —Tellería, J.L. (2018). Distribution of the Red-backed Shrike Lanius collurio at its western range boundary: patterns and conservation prospects. Ardeola, 65: 221–232.