Ficedula Hypoleuca Research Articles

Age-specific reproduction in female pied flycatchers: evidence for asynchronous aging

Age-related variation in reproductive performance is central for the understanding of population dynamics and evolutionary processes. Our understanding of age trajectories in vital rates has long been limited by the lack of distinction between patterns occurring within- and among-individuals, and by the lack of comparative studies of age trajectories among traits. Thus, it is poorly understood how sets of demographic traits change within individuals according to their age. Based on 40 years of monitoring, we investigated age-related variation in five reproductive traits in female pied flycatchers (Ficedula hypoleuca) including laying date, clutch size, brood size, nest success (probability that a nest produces at least one chick) and egg success of successful nests (proportion of eggs resulting in a chick). We disentangled within- from among-individual processes and assessed the relative contribution of within-individual age-specific changes and selective appearance and disappearance. Finally, we compared the aging pattern among these five reproductive traits. We found strong evidence for age-specific performance including both early-life improvement and late-life decline in all reproductive traits but the egg success. Furthermore, the aging patterns varied substantially among reproductive traits both for the age of peak performance and for the rates of early-life improvement and late-life decline. The results show that age trajectories observed at the population level (cross-sectional analysis) may substantially differ from those occurring at the individual level and illustrate the complexity of variation in aging patterns across traits.

The role of introductory alarm calls for song discrimination in Ficedula flycatchers

Assortative mating depends on species distinctiveness in mating traits and preferences, which can be challenging to maintain when traits and/or preferences are learned. This is because learning may cause individuals to copy heterospecific signals. Juvenile songbirds possess innate sensory biases favouring them to learn and to prefer conspecific songs, but the effectiveness of these biases relies on consistent and sufficient differences between the songs produced by different species. However, mating signals, including learned songs, sometimes converge in sympatry, and the species-specific cues that individuals use to shape their preferences are often unknown. In Ficedula flycatchers, a stereotyped and highly species-specific alarm call is often incorporated as the first syllable of their songs. However, where the two species co-occur, pied flycatchers, Ficedula hypoleuca , learn to incorporate the introductory calls of the closely related collared flycatcher, Ficedula albicollis , into their songs. In this study, we investigated the role of introductory alarm calls for song discrimination in collared flycatchers, using playback experiments of both manipulated and unmanipulated songs on adults and nestlings within the hybrid zone of Öland, Sweden. We predicted that the introductory alarm call would be sufficient to trigger song responses, such that adults and nestlings would respond similarly to song phrases including the call, whether it is followed by conspecific or heterospecific notes. Our results provide evidence that the introductory alarm call is sufficient to trigger song discrimination in nestlings, but not in adult males, potentially due to their greater experience with songs and, therefore, subtler discrimination. Altogether, this study highlights the often-overlooked importance of calls within or associated with songs. • Collared flycatchers often start their songs with an alarm call. • The alarm call seems sufficient to drive song responses in nestlings. • We argue that the call could guide learning onto appropriate songs. • However, the call alone is unlikely to be sufficient for discrimination in adults. • We discuss the broader implication of incorporation of calls into songs.

No evidence that nest site choice in Pied Flycatchers is mediated by assessing the clutch size of a heterospecific, the Great Tit

Among species that use similar resources, an individual may benefit by observing and copying the behavioural decision of a heterospecific. We tested the hypothesis of heterospecific social learning in passerine birds, namely that a migrant species, the Pied Flycatcher Ficedula hypoleuca, uses external markings on the nest cavities of a resident species, the Great Tit Parus major, as cues when choosing a nest site. Others have suggested that prospecting flycatchers assess the clutch size of tit “demonstrators” by entering their nest boxes and, assuming that a large clutch indicates a high-quality individual, will copy the nest appearance of tits with large, but not small clutches. During a 4-year period in Norway, we designed a similar study but did not find that flycatchers based their nest choice on the clutch size of tits. Neither were there any relationships between clutch size of the tit and its laying date, incubation behaviour, or the number of eggs visible through nest material during egg-laying so Pied Flycatchers did not use these indirect cues to assess quality of the tutor. Filming of tit nests showed that prospecting flycatchers did not enter tit nest boxes to assess the content. Indeed, incubating female tits only left their nest boxes for short bouts of unpredictable duration so there was little opportunity for flycatchers to inspect the nest contents unnoticed. Our study calls into question the mechanism of using the content of tit nests as public information for choosing traits of nest sites based on external characteristics. We suggest that similar studies of nest site choice in relation to possible social information transfer be replicated more widely.

Use of landmarks for nest site choice and small-scale navigation to the nest in birds

Abstract Nest sites of animals are often concealed to keep vulnerable offspring from being detected by predators. Parents may use landmarks near the nest to relocate it quickly. We allowed blue tits (Cyanistes caeruleus) to choose between two nest boxes fixed on the same tree with either none, the same, or different white painted markings. Surprisingly, the female brought material to both boxes and sometimes laid eggs in both. In a second experiment, we let pied flycatchers (Ficedula hypoleuca) and great tits (Parus major) become familiar with a marking on the initial nest box and then let them choose between two new nest boxes erected on different, nearby trees. Neither species preferred the box with the matching mark. In nature, the birds may locate the correct entrance of a cavity using other landmarks near the nest opening, like branches and the height of the cavity opening above the ground.

Phenology-mediated effects of phenotype on the probability of social polygyny and its fitness consequences in a migratory passerine

Why females engage in social polygyny remains an unresolved question in species where the resources provided by males maximize female fitness. In these systems, the ability of males to access several females, as well as the willingness of females to mate with an already mated male, and the benefits of this choice, may be constrained by the socio-ecological factors experienced at the local scale. Here, we used a 19-year dataset from an individual-monitored population of pied flycatchers (Ficedula hypoleuca) to establish local networks of breeding pairs. Then, we examined whether the probability of becoming socially polygynous and of mating with an already mated male (thus becoming a secondary female) is influenced by morphological and sexual traits as proxies of individual quality relative to the neighbours. We also evaluated whether social polygyny is adaptive for females by examining the effect of females’ mating status (polygamously-mated vs monogamously-mated) on direct (number of recruits in a given season) and indirect (lifetime number of fledglings produced by these recruits) fitness benefits. The phenotypic quality of individuals, by influencing their breeding asynchrony relative to their neighbours, mediated the probability of being involved in a polygynous event. Individuals in middle-age (2–3 years), with large wings and, in the case of males, with conspicuous sexual traits, started to breed earlier than their neighbours. By breeding locally early, males increased their chances of becoming polygynous, while females reduced their chances of mating with an already mated male. Our results suggest that secondary females may compensate the fitness costs, if any, of sharing a mate, since their number of descendants did not differ from monogamous females. We emphasize the need of accounting for local breeding settings (ecological, social, spatial, and temporal) and the phenotypic composition of neighbours to understand individual mating decisions.

Effects of Variable Responses to Climate Change on the Interactions of Migratory and Resident Birds in Europe

Long-distance migrants and residents may respond to large-scale climate change by advancing egg laying dates. It is expected that variation in changes in avian laying dates among similar species affects their interactions in an ecological community. By analyzing long-term trends of the mean laying dates (MLD) of pied flycatcher Ficedula hypoleuca, collared flycatcher Ficedula albicollis, and great tits Parus major across 25 study sites in Europe from five published studies, the paper uses two-tailed t tests to show that variable adjustments in laying dates in different species have different implications on their interactions across Europe. It is found that pied flycatcher advanced laying dates significantly faster compared to great tits in Central Europe, gaining advantage in their competition for nest holes. Additionally, the study shows that pied flycatcher and collared flycatcher potentially share smaller overlap in laying dates in their sympatric breeding ground in Northern Europe, which may decrease the occurrences of hybridization, whereas the trend reverses in Central Europe. The results highlight that geographical variations in phenological responses to climate change have complicated effects on interspecific interaction, a novel research field that lacks empirical results. The conclusions of this study provide potential directions for empirical studies of climate change in the future.

The effects of four decades of climate change on the breeding ecology of an avian sentinel species across a 1,500-km latitudinal gradient are stronger at high latitudes.

Global warming affects breeding phenology of birds differentially with latitude, but there is contrasting evidence about how the changing climate influences the breeding of migrating songbirds at their northern breeding range. We investigate the effect of climate warming on breeding time and breeding success of European pied flycatchers Ficedula hypoleuca in Sweden during a period of 36 years using nest reports from bird ringing. To account for the latitudinal variation, we divided Sweden into three latitudinal bands (northern, intermediate, and southern). We applied a sliding window approach to find the most influential period and environment characteristics (temperature, vegetation greenness, and precipitation), using linear mixed models and model averaging. Our results show a long‐term advancement of breeding time related to increasing spring temperature and vegetation greenness during a period before hatching. Northern breeders revealed a larger advancement over the years (8.3 days) compared with southern breeders (3.6 days). We observed a relatively stronger effect of temperature and greenness on breeding time in the north. Furthermore, northern birds showed an increase in breeding success over time, while birds breeding at southern and intermediate latitudes showed reduced breeding success in years with higher prehatching temperatures. Our findings with stronger environment effects on breeding time advancement in the north suggest that pied flycatchers are more responsive to weather cues at higher latitudes. Breeding time adjustment and, potentially, low competition help explain the higher long‐term success observed in the north. Reduced breeding success at more southerly latitudes suggests an inability to match breeding time to very early and warm springs, a fate that with continued climate change could also be expected for pied flycatchers and other long‐distance migrants at their very northern breeding range.

Trophic match/mismatch and reproduction of the pied flycatcher Ficedula hypoleuca in a metal-polluted area.

In polluted areas, birds can suffer from changes in diet composition and inferior food quality. It is unknown if pollution can desynchronize the phenology of birds and their prey, resulting in a mismatch between food demand and availability. For 2 years, we studied seasonal changes in the biomass of leaf-eating invertebrates and the timing of reproduction and breeding success of an insectivorous bird, the pied flycatcher, in an area heavily polluted by the Middle Ural copper smelter and in an unpolluted control area. Seasonal variations in herbivore biomass were relatively synchronous in polluted and unpolluted areas, whereas birds started breeding later in the polluted area. In the year with an earlier spring, the herbivore peak was early and short, resulting in lower food availability for birds feeding nestlings. The greater the mismatch between food demand and availability the higher was the frequency of nests containing perished nestlings and the lower the body mass of fledglings. Our data did not support the hypothesis that the detrimental effect of the trophic mismatch on birds is greater in the polluted area than in the unpolluted one. Nevertheless, delayed breeding in the pied flycatcher in polluted areas suggests a higher probability of mistimed bird reproduction in the years with a short period of food abundance. Thus, the synchrony of phenology of birds and their prey is an important pollution-related factor that should be taken into account when analyzing the effects of pollution on birds.

Ontogeny of the star compass in birds: pied flycatchers (Ficedula hypoleuca) can establish the star compass in spring

The star compass of birds, as well as the sun compass, is not innate. To possess either of them, the birds have to observe the rotating sky and determine its' center of rotation (in the star compass case) or the sun's movement (in the sun compass). Young birds are believed to learn how to use the star compass before their first migration, even though the evidence of this is lacking. Here, we test whether hand-raised Pied flycatchers (Ficedula hypoleuca) which had not established the star compass prior to their first autumn migration can gain it later in their ontogeny, in spring. We also attempted to examine if the observation of diurnal celestial cues (the sun and the polarized light) prior to autumn migration would affect the process of the star compass learning in spring. When tested in the vertical magnetic field under the natural starry sky, the group of birds which observed the stars in spring as the first celestial cues could choose the migratory direction. In contrast, the birds, which had never seen the stars, were not able to use the nightly celestial cues in the vertical magnetic field. However, the group of birds which had seen the daytime celestial cues till autumn and the stars at spring was disoriented, although this might be due to the small sample size. Our data suggest the possibility that the star compass may be learned in spring and emphasize the necessity for the further research in the interaction of celestial compasses.

Latitudinal variation in arrival and breeding phenology of the pied flycatcher Ficedula hypoleuca using large‐scale citizen science data

Many species have advanced the timing of annual reproductive cycles in response to climatic warming, sometimes leading to asynchrony between trophic levels, with negative population consequences. Long‐distance migratory birds, reliant on short seasonal food pulses for breeding, are considered particularly susceptible to such disjunction because late arrival may preclude optimal timing of egg‐laying. It is unknown whether the relative timing of arrival and egg‐laying is sufficiently plastic, in time and space, to enable an adaptive response when arrival times change relative to local food resources. We used citizen science data, describing pied flycatcher Ficedula hypoleuca arrival and egg‐laying dates, to explore temporal (2013–2016) and spatial (across Great Britain) variation in the phenology of arrival, laying and their difference. To assess the long‐term trend in arrival and laying at a single location, we used data from a long‐term field study. The arrival‐laying interval was consistently shorter in the north, driven by the contrast between spatial variation in arrival date and spatial invariance in laying date. To understand whether a short arrival‐laying interval may have consequences for productivity, we assessed the association between this interval and clutch size. We found no statistically significant correlation between these two variables. To examine long‐term changes in arrival and laying dates, we focussed on a single location in southwestern England. Both dates of first male arrival and first egg laid in a season advanced since 1986, with no evidence of interval shortening. Together, our results demonstrate spatial and annual variation in the arrival‐laying interval, with no detected effect on fecundity. Thus, the interval from arrival to laying is likely dictated by spatially and temporally varying local conditions, suggesting these migrant birds may have the ability to adapt this interval to align with local conditions and mitigate potential mismatch impacts.

Adaptive coloration in pied flycatchers (Ficedula hypoleuca)-The devil is in the detail.

Understanding the origin and persistence of phenotypic variation within and among populations is a major goal in evolutionary biology. However, the eagerness to find unadulterated explanatory models in combination with difficulties in publishing replicated studies may lead to severe underestimations of the complexity of selection patterns acting in nature. One striking example is variation in plumage coloration in birds, where the default adaptive explanation often is that brightly colored individuals signal superior quality across environmental conditions and therefore always should be favored by directional mate choice. Here, we review studies on the proximate determination and adaptive function of coloration traits in male pied flycatchers (Ficedula hypoleuca). From numerous studies, we can conclude that the dark male color phenotype is adapted to a typical northern climate and functions as a dominance signal in male–male competition over nesting sites, and that the browner phenotypes are favored by relaxed intraspecific competition with more dominant male collared flycatchers (Ficedula albicollis) in areas where the two species co‐occur. However, the role of avoidance of hybridization in driving character displacement in plumage between these two species may not be as important as initially thought. The direction of female choice on male coloration in pied flycatchers is not simply as opposite in direction in sympatry and allopatry as traditionally expected, but varies also in relation to additional contexts such as climate variation. While some of the heterogeneity in the observed relationships between coloration and fitness probably indicate type 1 errors, we strongly argue that environmental heterogeneity and context‐dependent selection play important roles in explaining plumage color variation in this species, which probably also is the case in many other species studied in less detail.

Three Decades of Crimes and Misdemeanours in the Nest Box Life of European Pied Flycatchers Ficedula hypoleuca

Pied Flycatchers Ficedula hypoleuca are known to be victims of nest killings in contexts of competition for nest boxes. However, there is only anecdotal information on their opposite role as perpetrators of nest takeovers and occasional killings of other songbirds. Over 31 years we examined whether competition with Great Tits Parus major over nest box ownership is a significant source of mortality for Pied Flycatchers and whether the increase in Pied Flycatcher populations affected the use of nest boxes by the smallest tit species, the Blue Tit Cyanistes caeruleus and Coal Tit Periparus ater, in two forests in the central Iberian Mountain Range. We found 31 Pied Flycatchers killed inside nest boxes. The Great Tit was the most frequent species to which the killings were attributed. Followed by Pied Flycatchers themselves and Nuthatches Sitta europaea. We confirmed the killing by Pied Flycatchers of at least two conspecific males and one incubating female Coal Tit, with one killer male identified. Large increases in population densities of flycatchers after nest box deployment in the two study areas seem to have triggered an intensification of agonistic interactions among their potential occupants, resulting in an increase of takeovers by Pied Flycatchers of nest boxes initially owned by the smallest tit species. Great Tits are not a serious threat for Pied Flycatchers breeding in the study area, most likely due to their preference for natural holes over the nest box types most frequently installed. The interactions of Pied Flycatchers with Blue and Coal Tits for the ownership of nest boxes do not seem to cause significant mortality in the species involved. However, aggressive usurpations of nest boxes by Pied Flycatchers surely have negative impacts on the reproductive success of the victims through their eviction from suitable nesting sites.—Potti, J., Camacho, C., Canal, D. & Martínez-Padilla, J. (2021). Three decades of crimes and misdemeanours in the nest box life of European Pied Flycatchers Ficedula hypoleuca. Ardeola, 68: 315-333.

Identifying the paths of climate effects on population dynamics: dynamic and multilevel structural equation model around the annual cycle

How environmental factors influence population dynamics in long-distance migrants is complicated by the spatiotemporal diversity of the environment the individuals experience during the annual cycle. The effects of weather on several different aspects of life history have been well studied, but a better understanding is needed on how weather affects population dynamics through the different associated traits. We utilise 77 years of data from pied flycatcher (Ficedula hypoleuca), to identify the most relevant climate signals associated with population growth rate. The strongest signals on population growth were observed from climate during periods when the birds were not present in the focal location. The population decline was associated with increasing precipitation in the African non-breeding quarters in the autumn (near the arrival of migrants) and with increasing winter temperature along the migration route (before migration). The number of fledglings was associated positively with increasing winter temperature in non-breeding area and negatively with increasing winter temperature in Europe. These possible carry-over effects did not arise via timing of breeding or clutch size but the exact mechanism remains to be revealed in future studies. High population density and low fledgling production were the intrinsic factors reducing the breeding population. We conclude that weather during all seasons has the potential to affect the reproductive success or population growth rate of this species. Our results show how weather can influence the population dynamics of a migratory species through multiple pathways, even at times of the annual cycle when the birds are in a different location than the climate signal.

The extent of white plumage patches in female Pied Flycatchers Ficedula hypoleuca is negatively associated with corticosterone concentration in partly unpigmented feathers

Sexually and socially selected signals are predicated to express the present and past condition of individuals and thereby their capacity to cope with environmental challenges. The concentration of corticosterone in feathers (CORTf) has been validated as a marker of activation of the hypothalamic-pituitary axis in birds during feather development. Measurements of CORTf can thus express the physiological stress of migratory birds during non-breeding periods of the annual cycle when feathers moulted in the wintering range are analysed. Thus, negative trends of ornament expression with CORTf may be predicted. Unpigmented plumage patches may constitute signals of phenotypic quality and are used in many species in social interactions by both sexes. Pied Flycatchers of both sexes Ficedula hypoleuca show white forehead and wing patches during the breeding season, of which the forehead and part of the wing patch (tertials) are moulted on the wintering grounds before spring migration. These patches are used as signals in social and sexual interactions and their expression has been previously related to several indicators of physiological status. We collected tertials of females during nestling provisioning in a Spanish population and determined their CORTf in the laboratory. CORTf was thus measured in some of the prenuptially moulted feathers used as signals of social dominance by breeding females. According to AICc model selection, CORTf turned up in all the best models explaining forehead patch size and in most best models for wing patch size when controlling for age and size. Both forehead and wing patch sizes were negatively related to CORTf, although the trend for wing patch size was not significant. This indicates that breeding females expressing large unpigmented patches experienced low levels of stress during the prenuptial moult in their winter quarters, or that strongly signalling individuals present a lower level of activation of the HPA axis.

Dalmatian: A Package for Fitting Double Hierarchical Linear Models in R via JAGS and nimble

Traditional regression models, including generalized linear mixed models, focus on understanding the deterministic factors that affect the mean of a response variable. Many biological studies seek to understand non-deterministic patterns in the variance or dispersion of a phenotypic or ecological response variable. We describe a new R package, dalmatian, that provides methods for fitting double hierarchical generalized linear models incorporating fixed and random predictors of both the mean and variance. Models are fit via Markov chain Monte Carlo sampling implemented in either JAGS or nimble and the package provides simple functions for monitoring the sampler and summarizing the results. We illustrate these functions through an application to data on food delivery by breeding pied flycatchers (Ficedula hypoleuca). Our intent is that this package makes it easier for practitioners to implement these models without having to learn the intricacies of Markov chain Monte Carlo methods.

Interspecific aggression and defence of extra nest sites in two species of songbirds

AbstractInterspecific competition is expected when two species share resource needs. For example, secondary cavity‐nesting birds may compete vigorously for suitable nest sites both within and among species. However, little is known of whether monogamous species defend more than one nest site on their territory after breeding has begun, and in particular whether they are aggressive against other species. Defending extra nest sites may be adaptive because they may be used for renesting after a failure or to produce a second brood. We studied interactions between a monogamous, resident bird, the great tit Parus major and a migrant, the pied flycatcher Ficedula hypoleuca, providing nest boxes in woodlands in Norway. Agonistic behaviours may be subtle and easily overlooked so we experimentally placed caged male pied flycatchers near nests of great tits and at a dyad of empty nest boxes erected in the territory 25 m away. We filmed interactions between species at 21 sites in the egg‐laying period of the tit, and at 26 nest sites during incubation. Male great tits showed aggression towards the caged flycatcher both at their own nest box and at the nest boxes erected at a distance. We manipulated the external appearance of the nest boxes with painted designs around the entrances but the intensity of aggression at the empty nest boxes did not depend on whether those boxes matched the nest box with the tit nest and was not correlated with tit clutch size. Neither was the intensity of display activity at each nest box by the flycatchers that settled associated with these variables. The results are discussed in relation to hypotheses for nest site choice involving interspecific social learning and aggression.

Bird Feces as Indicators of Metal Pollution: Pitfalls and Solutions.

Bird feces are commonly used as a proxy for measuring dietary metal exposure levels in wild populations. Our study aims to improve the reliability and repeatability of fecal metal measurements and gives some recommendations for sampling. First, we studied levels of variation in metallic element (arsenic, calcium, cadmium, cobalt, copper, nickel, lead) concentrations: temporal variation within an individual, among siblings in a brood and among-brood/spatial variation. Second, we explored the variation caused by dual composition (urate vs. feces) of bird droppings. Two sets of fresh fecal samples were collected from pied flycatcher (Ficedula hypoleuca) nestlings living in a metal polluted area in summers 2017 (dataset 1) and 2018 (dataset 2). We found a great deal of temporal intra-individual variation in metal levels, suggesting that dietary exposure varied markedly in a short time scale (within a day). A sample from only one nestling per brood did not well describe the brood mean value, and we recommend that at least four siblings should be sampled. Brood level samples give relatively good temporal repeatability for most metals. For all the metals, the levels in the fecal portion were more than double to those in the urate portion. Since the mass proportion of urate in the bird droppings varied a great deal among samples, standardizing sampling, e.g., by collecting only the fecal part, would markedly reduce the variation due to composition. Alternatively, urate portion could be used for biomonitoring of internally circulated bioavailable metal.

Association of Success in Interspecific Rearing of Nestlings with the Width of Trophic Niche of the Recipient Species in Hollow-Nesting Birds

The structure of the diet of passerine bird nestlings was analyzed in order to identify possible ways to reduce food competition between these species during the breeding period. We assumed that analysis of the effects of obtaining diets of heterospecific birds by nestlings in nature can help better understand their species-specific adaptations to living conditions, and we considered the case of joint nesting of the coal tit (Periparus ater (L. 1758)) (CT) and pied flycatcher (Ficedula hypoleuca (Pallas 1764)) (PF) in Moscow oblast as a key link. A PF male attracted a female to an artificial nest box, which has been already occupied by a CT pair. The females of both species incubated a mixed clutch sitting side by side. The CT nestlings hatched earlier than the PF nestlings, and the parents of both species began to feed them. The CT nestlings started to die one by one on the 4th day of joint feeding, and the last nestling died on the 11th day. This case encouraged us to compare the diets of nestlings from 22 broods of CTs and PFs in the same region. To compare the ratios of nestlings, we collected the portions of food that were delivered to nestlings by their parents and analyzed video recordings from the nests. The diet of PF nestlings was significantly more diverse than in CT nestlings (Berger–Parker reverse indices (1/d) were 3.01 and 2.11, respectively). Caterpillars and spiders (objects with a high content of carotenoids and taurine important for the development of nestlings) dominated in the CT diet. In PF feed, these objects occupied a much smaller portion. In addition to the above, compared with coal tits, PFs brought the following to nestlings: a significant number of objects with rough, highly chitinized covers (Coleoptera, Homoptera, etc.); objects with a sharp taste, such as true bugs (Heteroptera), ladybirds (Coleoptera, Coccinellidae), and millipedes (Diplopoda, Julidae); insects containing cantharidin toxin (soldier beetles, Coleoptera, Cantharidae). The nestlings developed successfully in PF nests to which parents brought such feed objects. The dimensional ranges of objects in the CT and PF diets completely overlapped. According to our opinion, the rougher, highly chitinized food and some poisonous insects (Cantharidae) in the PF diet make fundamentally important differences in the nutrition of PFs and CTs. Most likely, PFs have resistance to cantharidin and some other toxins that are contained in insects and therefore have a wider trophic niche.

Increased Stopover Duration and Low Body Condition of the Pied Flycatcher (Ficedula hypoleuca) at an Autumn Stopover Site.

Simple SummaryMany bird species that migrate long distances are in decline partly because of environmental changes, such as climate change or land-use changes. Although much is already known on the effects of environmental change on birds that are on their spring migration or on their breeding grounds, little is known with regard to possible negative effects on birds that are on their autumn migration and visiting so-called stopover sites on their way to their wintering grounds. These stopover sites are vital for birds to refuel, and a potential deteriorating quality of the stopover sites may lead to individuals dying during migration. We investigated the impacts of local environmental conditions on the migration strategy and body condition of the Pied Flycatcher at an autumn migration stopover site using long-term ringing data and local environmental conditions. We found that although birds arrived and departed the stopover site around the same time over the years, the body condition of the individuals caught decreased, and the length of their stay at the stopover site increased. This suggests that conditions at the stopover site during the autumn migration period have deteriorated over time which may lead to the death of more birds during autumn migration.Many long-distance migratory bird species are in decline, of which environmental changes, such as climate change and land-use changes, are thought to be important drivers. The effects of environmental change on the migration of these birds have often been studied during spring migration. Fewer studies have explored the impacts of environmental change on autumn migration, especially at stopover sites. However, stopover sites are important, as the quality of these sites is expected to change over time. We investigated impacts of local environmental conditions on the migration strategy and body condition of the Pied Flycatcher (Ficedula hypoleuca) at an autumn migration stopover site using long-term ringing data (1996–2018) and local environmental conditions. We found that although the arrival and departure dates of birds at the stopover site remained unchanged, the body condition (fat score) of the individuals caught decreased, and the stopover duration increased. This suggests that conditions at the stopover site during the autumn migration period have deteriorated over time. This study emphasizes the importance of suitable stopover sites for migratory birds and stresses that changes in environmental conditions during the autumn migration period may be contributing to the current decline in long-distance migratory passerines.

Breeding biology and long-term population dynamics of the Pied Flycatcher Ficedula hypoleuca in Skibotn, Northern Norway

Abstract. The breeding biology and population dynamics of the Pied Flycatcher Ficedula hypoleuca in pine, mixed and deciduous forests in Skibotn, Northern Norway (69°20’N, 20°20’E), was studied during 33 years (1987–2019; in total 1775 completed first clutches). It was a period during which summer temperatures remained relatively stable, but late spring (May) temperatures tended to become warmer. The number of breeding pairs declined over the study period but varied less than in populations living in more harsh subalpine environments. In spite of the northern location, females started to lay eggs in a relatively late phenological phase of the environment and in relatively warm weather. The date of birch leafing and the date of egg-laying advanced during the study period, and they correlated with each other. Mean clutch size was 6.4 eggs, and mean number of fledglings/nest 4.6. Date of egg-laying was earlier and clutch size larger in deciduous forests than in pine and mixed forests, but this did not translate into better fledgling productivity. The main causes of nesting failure were predation by small mustelids and starvation in warm and dry summers. However, in the long run the population seemed to be able to maintain itself without immigration, i.e., act as a source population. The possibility that during warm climate periods of the past, breeding biology and population dynamics of Pied Flycatchers over large geographical areas might have resembled those in Skibotn is discussed.
 
 Cover photo: “Mummified” Pied Flycatcher nestling (age about 10 days) starved to death in Skibotn in the warm and dry summer of 1988. Photo: Antero Järvinen.