Search

Theoretically, seasonal changes in immune functioning in animals are shaped by the trade-off between a probability of encountering pathogens and availability of resources. We used leukocyte profile (absolute and relative leukocyte counts) as a simple measure of immune system condition to study how it changes during the transition from postjuvenile molt to autumn migration in a free-living migratory songbird, the Eurasian blackcap (Sylvia atricapilla). We observed the higher white blood cells (WBC) and lymphocyte counts in molting birds compared to migrating individuals, but we did not find differences in heterophils and ratio of heterophils to lymphocytes (HL ratio). We suppose that the high number of WBC in molting blackcaps could reflect the heightened ability of their immune system to resists infections. The lower WBC counts in migrants compared to molting birds were mostly due to reduced lymphocyte numbers, thus representing in a downregulation of specific immunity. An absence of heterophil differences between molt and migration might indicate that various components of immunity can change relatively independently (or at different pace). Fat scores had no effect on WBC counts and HL ratio. Therefore, we found no strong evidence for a resource-immune functionality trade-off during transition from postjuvenile molt to autumn migration in immature Eurasian blackcap. This study is an important step in understanding how immune system in general and leukocyte profile in particular changes in transition between life-history stages in migratory songbirds.

Hippoboscid flies, also known as louse flies, are obligate blood-feeders ectoparasites of birds and mammals. By studying louse fly parasites of four Passeriformes species, Eurasian blackbird (Turdus merula), Eurasian blackcap (Sylvia atricapilla), common chaffinch (Fringilla coelebs) and European robin (Erithacus rubecula), with dissimilar time of colonization of Azores islands, we tested whether: (i) island host populations have lower parasite richness than the mainland one; (ii) island host populations undergo higher parasite prevalence, mean intensities and mean abundance than the mainland one; (iii) island parasite diversity are composed exclusively by specific parasites and (iv) parasite richness is positively correlated with the island area and proximity to the continent. For these purposes, 775 birds were sampled for presence of louse flies, by modified fumigation chamber method, from Azores Islands (São Miguel, Terceira and Flores) and Portugal mainland. Insular and mainland parasite assemblages were statistically compared. We record for the first time to Azores, Ornithomya fringillina and Icosta minor from Portugal mainland. Louse flies had highest prevalence and abundance from Azores Islands compared to those observed in mainland birds, especially blackbirds. The insular parasite diversity of Azores blackbirds, blackcaps and chaffinches was richer than the one observed in mainland population. None of the hippoboscid flies observed on the islands and mainland were host-specific. Thus, our findings provide an upgrade of parasite island syndromes knowledge, in the context of the ectoparasites, namely to the hippoboscid flies case., Graphical abstract Image 1, Highlights • We investigate the louse flies of four Passeriformes species from Macaronesia. • Louse flies of Azores blackbirds had highest prevalence than in mainland birds. • Insular parasite diversity was richer than the one observed in mainland population. • Hippoboscid flies observed on the islands and mainland were not host-specific. • Ornithomya fringillina recorded for the first time to Azores.

Changes in biometric characteristics of a migrating bird population at a given capture site could reflect that the migration strategies of the species may be changing. A robust data set (15,520 records) was used to analyse the changes in biometric characteristics of the Eurasian Blackcap Sylvia atricapilla in western Hungary between August and October during the study period (2001–2019). All age and sex classes displayed similar phenology of monthly captures and biometric change: the average wing length, fat score and body mass increased in the migrating population from August to October. This could be explained by changes in the morphometric distribution of different migrating populations, in later months more birds might arrive from a larger distance, primarily from the Baltic regions and the Czech Republic. The biometrics of juvenile birds captured in August did not change significantly from 2001 to 2019, while the wing lengths decreased and fat scores increased significantly between 2001 and 2019 in September and October in both sex classes. This could be explained by a change in the migration distance or different morphology of individuals from the north which stopped over at the study area. Due to the global warming and habitat changes in the last decade, the shorter migration route and favourable conditions at overwintering areas north of the Sahara or around the Mediterranean could favour Blackcaps which migrate a shorter distance.

Searching for specific antibodies in bird serum could reveal arbovirus activity in certain localities. To date, no systematic surveillance for arbovirus infection in autochthonous population of wild birds has been conducted in Slovakia. Present study includes birds captured on spring migration and birds of the autochthonous nesting population of the Drienovska wetland (Slovakia). Serum samples were tested for West Nile virus (WNV), Usutu virus (USUV), Tick-borne encephalitis virus (TBEV) and Tribec virus (TRBV) neutralizing antibodies (NAb). Blood samples were collected during 2017 spring migration (March – April) and from local breeders and hatched juveniles (May – July) caught by Constant Effort site ringing method. Specific NAb were detected by micro-titration virus neutralization test. WNV NAb were detected in 11.7% (18/153) of sampled birds. Ten WNV seropositive were migrants (Eurasian Robins, Eurasian Blackcap and a Great Tit), 5 were nesting adults (Song Thrush, White Throat, Eurasian Jay, Hawfinch and Eurasian Blackbird) and 3 were juveniles (Song Thrush, Common Starling and a Great Tit). There was not confirmed USUV infection in any of the examined birds. TBEV NAb were detected during breeding season in the adult Eurasian Blackcap, which means 1.1% (1/93) seropositivity. TRBV NAb was detected in 7.4% (5/68) of adult birds (Eurasian Blackbirds and a Common Starling) and in one juvenile Great Tit, which had also WNV Nab as well. These results suggest active transmission of at least two arboviruses in the autochthonous avifauna in Slovakia.

Moult of birds is shaped by environmental and genetic drivers whose relative contribution to the structure of feathers may differ within and between populations. In this study, we compare some traits of tail feathers (growth bars, mass, rachis width and barb length) between four populations of the Eurasian blackcap Sylvia atricapilla breeding at different elevations within the southwestern Palaearctic. We tested if these traits were related to the primary productivity of habitats (a surrogate of food availability) or were better explained as an adaptation to altitudinal movements. The distribution of primary productivity was positively related to blackcap abundance suggesting that the species tracked the most productive areas to breed. In this environmental setting, wing morphology (wing length, concavity and pointedness) suggested that lowland blackcaps were sedentary while blackcaps from highland areas were involved in altitudinal movements. The feathers of blackcaps inhabiting the highlands showed wider growth bars and rachis than those of the most productive lowland areas but did not differ in feather mass and barb length. Fast feather growth has been related to time constraints to moult and wider rachis to improve flight efficiency in migratory birds. Our results therefore suggest that differences in feather characteristics between southern populations of the Eurasian blackcap are better interpreted as an adaptive response to altitudinal migration than as a consequence of regional food availability.

1. The recent boost in bird migration studies following the development of various tracking devices raised awareness of how detrimental attaching devices can be for animals. Such effects can occur during migration, but also immediately post-release if the device impairs escape flight performance and, consequently, the bird’s ability to evade predators. 2. In this study, we investigated the effect of carrying a device on the escape flight speed and aerodynamic force production in a migratory passerine. We recorded upward-directed escape flights of 15 male blackcaps. Each individual was tested without a tag, and when equipped with three different leg-loop dummy tags with masses representing around 3%, 5% and 7% of their body mass. The experiment was designed such that all individuals passed through all treatments in a randomized order. 3. We found that two factors affected flight speed in roughly equal amounts: first, tagged escape flights had lower flight speeds compared to the control flights, irrespective of tag mass. Second, we found an effect of the total mass, i.e. the sum of the masses of the individual bird and of the tag, with heavier birds being slower. In contrast, flight speed was not correlated with relative tag mass in percentage of body mass, the metric commonly used in ethical guidelines for tag attachment. Aerodynamic flight force production also depended on total mass, with heavier birds producing higher forces. But these flight forces did not differ between flights with or without a tag. 4. We conclude that, when tagging birds, it is misleading to choose heavy individuals for tagging in order to minimize the tag mass as a percentage of body mass. This is particularly relevant in species for which body mass is not necessarily related to size, like migratory birds that accumulate large fat reserves. The lower escape speed in “tagged” flights could not be explained by differences in net flight force production, because these did not differ between flights with and without a tag. This suggests that the tag also affected pre-flight take-off dynamics, possibly due to a leg harness-induced reduction in leg push-off performance.

The relationship between the temperature, the precipitation of the breeding season’s months, and the annual proportions of the first year birds such as the indicators of the breeding success were examined by canonical correspondence analysis (CCA) having targeted nine common passerine species. The results of our study have shown that the high April and May temperature has been favourable for the breeding of the partial and the short-distance migrants, the common blackbird (Turdus merula) and the Eurasian blackcap (Sylvia atricapilla). This is confirmed by the fact that the highest annual capture (164) of the hatching year of the Eurasian blackcap was in 2009, when there was the mildest April during the study period (13.57°C), while the lowest annual capture (15) was in 2002, when there was the second coolest April (9.78°C). The common chiffchaff (Phylloscopus collybita) was a wet spring-tolerant species. There was negative correlation between April, May, June temperature and proportion of young great tit. The relationships between the annual captures of first year birds and the climate variables could not be identified with the methods used for the European robin (Erithacus rubecula), the common whitethroat (Sylvia communis), the lesser whitethroat (Sylvia curruca) and the blue tit (Parus caeruleus). The temperature in July was the most important climate factor for the breeding success of the long-distance migrant European pied flycatcher (Fycedula hypoleuca).

Frugivores are critical components of restoration programs because they are seed dispersers. Thus, knowledge about bird-plant trophic relationships is essential in the evaluation of the efficacy of restoration processes. Traditionally, the diet of frugivores is characterized by microscopically identifying plant residues in droppings, which is time-consuming, requires botanical knowledge, and cannot be used for fragments lacking detectable morphological characteristics (e.g., fragmented seeds and skins). We examined whether DNA barcoding can be used as a universal tool to rapidly characterize the diet of a frugivorous bird, Eurasian blackcap (Sylvia atricapilla). We used the DNA barcoding results to assess restoration efforts and monitor the diversity of potentially dispersed plants in a protected area in northern Italy. We collected 642 Eurasian Blackcap droppings at the restored site during the autumn migration over 3 years. Intact seeds and fragmented plant material were analyzed at 2 plastidial barcode loci (rbcL and trnH-psbA), and the resulting plant identifications were validated by comparison with a reference molecular data set of local flora. At least 17 plant species, including 7 of the 11 newly transplanted taxa, were found. Our results demonstrate the potential for DNA barcoding to be used to monitor the effectiveness of restoration plantings and to obtain information about fruit consumption and dispersal of invasive or unexpected plant species. Such an approach provides valuable information that could be used to study local plant biodiversity and to survey its evolution over time.

Human activities are causing rapid environmental change at a global scale. Urbanization is responsible for some of the most extreme human-altered habitats and is a known driver of evolutionary change, but evidence and understanding of these processes is limited. Here, we investigate the potential underlying mechanisms contributing to the contemporary evolution of migration behaviour in the Eurasian blackcap (Sylvia atricapilla). Blackcaps from central Europe have been wintering in urban areas of Britain with increasing frequency over the past 60 years, rather than migrating south to the Mediterranean. It has been hypothesized that the popularization of providing supplementary foods for wild birds within Britain may have influenced this marked migratory change, but quantifying the selective forces shaping evolutionary changes remains challenging. Using a long-term national scale data set, we examine both the spatial distribution and interannual variation in blackcap wintering behaviour in Britain in relation to supplementary food availability and local climate. Over a 12-year period, we show that blackcaps are becoming increasingly associated with the provision of supplementary foods in British gardens, and that the reliability of bird food supplies is influencing their winter distribution at a national scale. In addition, local climatic temperatures and broader scale weather variation are also important determinants of blackcap wintering patterns once they arrive in Britain. Based on our findings, we conclude that a synergistic effect of increased availability of feeding resources, in the form of garden bird food, coupled with climatic amelioration, has enabled a successful new wintering population to become established in Britain. As global biodiversity is threatened by human-induced environmental change, this study presents new and timely evidence of the role human activities can play in shaping evolutionary trajectories.

There is increasing evidence of adaptive preferential investment during moult in those feather tracts that are more advantageous for fitness. In this study, we assessed whether, after the manual removal of two functionally different flight feathers (one primary and one rectrix), birds from two common passerine species (Eurasian Blackcap Sylvia atricapillaand European Robin Erithacus rubecula) favoured the regeneration of primary (supposedly the most functionally important feathers) over rectrix feathers. Our results did not show differences between replaced primary and rectrix feathers in their final length, but demonstrated that the gap left by the loss of the primary feather was filled earlier, suggesting that a rapid repair of the most essential feather tracts is also evolutionarily advantageous during the adventitious replacement of plumage.

1. The recent boost in bird migration studies following the development of various tracking devices raised awareness of how detrimental attaching devices can be for animals. Such effects can occur during migration, but also immediately post-release if the device impairs escape flight performance and, consequently, the bird’s ability to evade predators. 2. In this study, we investigated the effect of carrying a device on the escape flight speed and aerodynamic force production in a migratory passerine. We recorded upward-directed escape flights of 15 male blackcaps. Each individual was tested without a tag, and when equipped with three different leg-loop dummy tags with masses representing around 3%, 5% and 7% of their body mass. The experiment was designed such that all individuals passed through all treatments in a randomized order. 3. We found that two factors affected flight speed in roughly equal amounts: first, tagged escape flights had lower flight speeds compared to the control flights, irrespective of tag mass. Second, we found an effect of the total mass, i.e. the sum of the masses of the individual bird and of the tag, with heavier birds being slower. In contrast, flight speed was not correlated with relative tag mass in percentage of body mass, the metric commonly used in ethical guidelines for tag attachment. Aerodynamic flight force production also depended on total mass, with heavier birds producing higher forces. But these flight forces did not differ between flights with or without a tag. 4. We conclude that, when tagging birds, it is misleading to choose heavy individuals for tagging in order to minimize the tag mass as a percentage of body mass. This is particularly relevant in species for which body mass is not necessarily related to size, like migratory birds that accumulate large fat reserves. The lower escape speed in “tagged” flights could not be explained by differences in net flight force production, because these did not differ between flights with and without a tag. This suggests that the tag also affected pre-flight take-off dynamics, possibly due to a leg harness-induced reduction in leg push-off performance.

Woodland birds have experienced widespread population declines across Europe, resulting partly from a decrease in management practices such as coppicing. Increasing fuelwood demand may reverse the decline of coppicing, making it timely to attempt a fuller understanding of its effects. Here, the impact of coppicing on year-round habitat use by adults and juveniles of 16 songbird species was quantified from a quasi-experimental study over 32 years (1978–2009) in Treswell Wood, Nottinghamshire, UK. Habitat use was inferred using capture rates from more than 10 000 h of mist-netting (> 25 000 captures) and detailed information on coppicing. Capture rates varied with coppice age in different ways: (1) increases as coppice aged (e.g. Marsh Tit Poecile palustris, juvenile Eurasian Treecreepers Certhia familiaris); (2) declines as coppice aged (e.g. Eurasian Blue Tit Cyanistes caeruleus, Great Tit Parus major); (3) peaks in capture rates at intermediate coppice age (i.e. 5–15 years) (e.g. Garden Warbler Sylvia borin, Willow Warbler Phylloscopus trochilus, adult Treecreepers); and (4) a peak at intermediate ages, followed by a decline, before an increase in use again at the oldest coppice ages (i.e. > 20 years) (e.g. Common Blackbird Turdus merula, Eurasian Blackcap Sylvia atricapilla, Eurasian Bullfinch Pyrrhula pyrrhula). Responses to coppice age were similar in different seasons, although Willow Tits Poecile montana showed little preference during breeding but avoided older coppice at other times. Juveniles and adults often differed in their responses to coppice age. The analyses reveal patterns in habitat use that are relevant to woodland management and conservation policy. They suggest that a mosaic of age structures in woodland is beneficial to a wide range of woodland species, and that management should consider the requirements of all age-classes of birds at different times of year.

Development during the relatively short time that young spend in the nest is crucial in a bird's life history. The rate of nestling growth strongly depends on numerous environmental and social factors, even within the same species or population. In the present study I examine the relative contributions of brood size, hatching asynchrony, hatching date and feeding rate in determining intraspecific variation in the growth of Eurasian Blackcap Sylvia atricapilla nestlings. I found a significant effect of brood size, hatching order and date on nestling development. However, the effect of hatching order and date was significant only for young nestlings and it gradually disappeared with nestling age. The only factor significantly affecting nestling development just before fledging was brood size. Nests of four siblings produced the heaviest young with the longest tarsi. This probably resulted from the highest feeding rate per nestling observed in broods of four nestlings. The study shows that for Blackcaps bree...

Reusing old nests for breeding might provide birds with benefits such as saving the time and energy needed to build a new nest, or by decreasing the risk of predation while building a nest. Despite these benefits, many species use their nests only once. This study aimed to determine how frequently Eurasian Blackcaps Sylvia atricapilla, which build delicate open cup nests that are particularly susceptible to damage, might reuse their nest within a season and if extensive damage to a nest limited its reuse. I conducted the study in 2002–2008 in forests next to the city of Bydgoszcz in central Poland. I examined 479 Blackcap nests after the failure or success of the nest was known. Nests were classified as damaged or undamaged (73.7% of the sample). Only four nests were reused, representing 0.8% of all nests and 1.1% of the undamaged nests. The large number of undamaged but inactive nests indicated that the extent of damage was unlikely to be the reason that nests were rarely reused. The study also showed th...

Migratory birds are known to use the Earth's magnetic field as an orientation cue on their tremendous journeys between their breeding and overwintering grounds. The magnetic compass of migratory birds relies on the magnetic field's inclination, i.e. the angle between the magnetic field lines and the Earth's surface. As a consequence, vertical or horizontal field lines corresponding to 0° or 90° inclination should offer no utilizable information on where to find North or South. So far, very little is known about how small deviations from horizontal or vertical inclination migratory birds can detect and use as a reference for their magnetic compass. Here we ask: what is the steepest inclination angle at which a migratory bird, the Eurasian blackcap (Sylvia atricapilla), can still perform magnetic compass orientation in Emlen funnels? Our results show that blackcaps are able to orient in an Earth's strength magnetic field with inclination angles of 67° and 85°, but fail to orient in a field with 88° inclination. This suggests that the steepest inclination angle enabling magnetic compass orientation in migratory blackcaps tested in Emlen funnels lies between 85 and 88 degrees.