Cinclus Cinclus Research Articles

Successful December nesting of a pair of White-throated Dippers (<i>Cinclus cinclus</i>) in Northeast Italy: the earliest ever in Europe

A remarkably early nesting of a pair of White-throated Dipper (Cinclus cinclus) in December 2021 in northeastern Italy is reported and discussed by considering factors that may have influenced the breeding onset.

Natal and breeding dispersal of the White-throated Dipper Cinclus cinclus in coastal rivers of the northern Iberian Peninsula

ABSTRACT Knowledge of avian dispersal patterns is basic to our understanding of the processes that characterise populations. We describe here the natal and breeding dispersal of White-throated Dippers Cinclus cinclus inhabiting three coastal catchments of the Basque Country, based on recaptures of ringed birds. Natal dispersal data were available for 70 Dippers, from a total of 789 nestlings ringed. Most of the birds (62.8%) were recaptured within 5 km of their natal nest (median 3.92 km). Natal dispersal differed between sexes, females moving longer distances than males. About 20% of the birds moved between catchments. Breeding dispersal data were available for 72 birds among 152 ringed adults. Both sexes showed strong fidelity to the breeding site. Only 8.7% of the birds recaptured changed their breeding site between seasons. These results are similar to those obtained in Britain, Ireland and central Europe, which suggests the existence of a shared pattern of dispersal among western European populations.

Post-Fledging Survival and Dispersal of the White-Throated Dipper Cinclus cinclus

The post-fledging period is still an understudied stage of avian life cycle, even in the case of otherwise frequently studied species. The general breeding biology of the White-throated Dipper is known well, but only a few studies have focused on survival and dispersal during the post-fledging period. In this study we report on results revealed by radio-telemetry, a method which has not been used in the species to date. Nestlings (37 individuals from 9 nests) in a mountain population of central Slovakia were radio-tagged on the mean expected fledging age (22 days post-hatch) and monitored daily until death, disappearance or reaching independence. Only 22–32% (depending on the handling of uncertain data) of fledglings survived the first 12 days post-fledging. Predation was the most frequently suspected cause of death. The daily survival rate was markedly lower during the first two days after fledging (0.717–0.758) than later (0.914–0.941). The daily movement distance remained stable during the first week post-fledging and increased around the age of reaching independence (c. 12 days post-fledging). On the other hand, the distance from the natal nest and the within-brood distance (length of river occupied by fledglings from the same nest) increased gradually since fledging. We propose that in our study population the low post-fledging survival could be potentially balanced by frequent renesting and/or double-brooding, timing of which corresponds well with the age of reaching independence when juvenile birds disperse outside the natal territory.

Reproductive senescence and mating tactic interact and conflict to drive reproductive success in a passerine.

An understanding of the drivers of individual fitness is a fundamental component of evolutionary ecology and life-history theory. Reproductive senescence, mate and mating tactic choice and latent heterogeneity in individual quality interact to affect individual fitness. We sought to disentangle the effects of these fitness drivers, where longitudinal data are required to understand their respective impacts. We used reproductive allocation and success data from a long-term (1989-2018) study of white-throated dippers Cinclus cinclus in Switzerland to simultaneously examine the effects of female and male age, mating tactic, nest initiation date and individual heterogeneity on reproductive performance. We modelled quadratic and categorical effects of age on reproductive parameters. The probability of polygyny increased with age in both sexes before declining in older age classes. Similarly, hatching probability in monogamous pairs and the number of nestlings hatched in both monogamous and polygynous pairs increased with female age before declining later in life. As predicted, offspring survival in monogamous pairs increased with male age before declining in older age classes, but male age had no effect on offspring survival in polygynous nesting attempts. Our results demonstrate that parental age, mating tactic and individual heterogeneity all affect reproductive success, and that the impacts of senescent decline are expressed across different demographic components as a function of sex-specific senescent decline and mating tactic.

Long-term annual and spatial variation of polygyny in the white-throated dipper (Cinclus cinclus).

Mating strategies are key components in the fitness of organisms, and notably in birds the occurrence of monogamy versus polygyny has attracted wide interest. We address this by a very comprehensive dataset (2899 breeding events spanning the years 1978–2019) of the white‐throated dipper Cinclus cinclus. Though the mating system of this species has been regarded as generally monogamous, we find that 7% of all breeding events were performed by polygynous males (approximately 15% of all pairs). The fraction of polygyny has been stable over the entire study period irrespective of population size. The assumption that polygyny is most common at low population density was not supported. Surprisingly, there was no difference between polygynous and monogamous males with regard to the quality of the territories they inhabited, ranked according to their overall frequency of use. The most common age group, first‐year breeders, dominated among monogamous males, while among polygynous males second‐year breeders were most common, followed by third and first‐year breeders. The primary females were in general older than females mated to monogamous males, also when controlled for their general frequency in the population. The majority of the two females mated to a polygynous male, bred in the vicinity of each other. The probability for a male to be involved in polygyny more than once, was significantly higher than by chance, suggesting phenotypic quality differences among males.

Breeding performance of the White-throated Dipper (Cinclus cinclus) under different temperature conditions

Many bird species breeding under optimal temperature conditions show higher reproductive success. However, less information can be found about how the reproductive output differs within one population and one breeding season. To find inter and intra-seasonal differences in several aspects of breeding ecology and breeding output we monitored 223 breedings of the White-throated Dippers within the three river basins of northern Slovakia (Central Europe) in 2010–2018. We registered the beginning of egg laying, clutch size, nest success and the proportion of second clutches. There were significant differences in egg-laying commencement between breeding seasons. The mean February and March temperature significantly influenced the first egg day (20 February–18 March), median laying date (8 March–6 April), the interval between the first and the last first egg in all clutches in one breeding season (37–50 days) and the proportion of second clutches (0.77%–0.95%). However, the differences were found not only between different seasons. The egg-laying initiation of individual nests within each season was considerable affected by the altitude and the proportion of second clutches of particular nests was significantly influenced by their timing of egg laying.

Hydrology influences breeding time in the white-throated dipper

BackgroundEarlier breeding is one of the strongest responses to global change in birds and is a key factor determining reproductive success. In most studies of climate effects, the focus has been on large-scale environmental indices or temperature averaged over large geographical areas, neglecting that animals are affected by the local conditions in their home ranges. In riverine ecosystems, climate change is altering the flow regime, in addition to changes resulting from the increasing demand for renewable and clean hydropower. Together with increasing temperatures, this can lead to shifts in the time window available for successful breeding of birds associated with the riverine habitat. Here, we investigated specifically how the environmental conditions at the territory level influence timing of breeding in a passerine bird with an aquatic lifestyle, the white-throated dipper Cinclus cinclus. We relate daily river discharge and other important hydrological parameters, to a long-term dataset of breeding phenology (1978–2015) in a natural river system.ResultsDippers bred earlier when winter river discharge and groundwater levels in the weeks prior to breeding were high, and when there was little snow in the catchment area. Breeding was also earlier at lower altitudes, although the effect dramatically declined over the period. This suggests that territories at higher altitudes had more open water in winter later in the study period, which permitted early breeding also here. Unexpectedly, the largest effect inducing earlier breeding time was territory river discharge during the winter months and not immediately prior to breeding. The territory river discharge also increased during the study period.ConclusionsThe observed earlier breeding can thus be interpreted as a response to climate change. Measuring environmental variation at the scale of the territory thus provides detailed information about the interactions between organisms and the abiotic environment.

Location Is Everything, but Climate Gets a Share: Analyzing Small-Scale Environmental Influences on Breeding Success in the White-Throated Dipper

Ecological and evolutionary effects of environmental variation on wild populations are of particular interest in a changing world. Large-scale environmental indices are classically used as environmental explanatory variables to study climate change effects on wild populations. However, these measures neglect the fact that individuals are affected by the local conditions in their home ranges. Freshwater ecosystems are particularly sensitive to climate change induced alterations in precipitation and discharge affecting lower trophic level prey and cascading up the food chain to impact keystone species. Here, we study how small-scale environmental variation at the level of each territory affects fitness-related traits and in particular reproductive success in the white-throated dipper Cinclus cinclus, a bird dependent on aquatic prey. We take advantage of a long-term study of breeding dippers in a natural river system in Norway (1978-2015). We relate daily river discharge and other important hydrological and territory location variables to clutch and brood size simultaneously, while accounting for female age, polygyny, and population density. We also address uncertainty in estimates of both clutch and brood size when modelling reproductive success. The most influential variable overall was the altitudinal gradient, where birds breeding at higher altitudes laid fewer eggs and fledged fewer young. Clutch size decreased with increased population density and high temperatures, while it was positively affected by female age. Brood size varied greatly among territories, where some territories had consistently larger broods than others. Increased minimum and maximum temperatures, river discharge above 10 l/s and increased variability in snow depth had a positive effect on brood size, whereas polygyny had a negative effect. In conclusion, territory-specific variables explained a large amount of the variation in the reproductive output in the dipper, emphasizing the importance of the local habitat, and not only climatic variation, in a keystone species in freshwater ecosystems.

Isospora dipperia n. sp. (Apicomplexa: Eimeriidae) from the American dipper Cinclus mexicanus Swainson (Passeriformes: Cinclidae) in Yosemite National Park, USA.

Isospora dipperia n. sp. is described from the feces of the American dipper Cinclus mexicanus Swainson collected in Yosemite National Park, California, USA. Sporulated oöcysts of the new species are subespherical, 20-24 × 17-21 (20.9 × 18.7) μm, with a length/width (L/W) ratio of 1.0-1.1 (1.1); one polar granule is present, but micropyle is absent. Sporocyts are lemon-shaped, 14-16 × 8-11 (15.5 × 9.8) μm, with a L/W ratio of 1.6; prominent Stieda and sub-Stieda bodies are both present, but para-Stieda body is absent. Sporocyst residuum of many scattered granules is present and the sporozoites have prominent anterior and posterior refractile bodies. The mean dimensions (15.9 × 13.8 µm) of unsporulated oöcysts of I. cincli Gottschalk, 1972 from the white-throated dipper C. cinclus (L.) in Europe, appear to be considerably smaller than those in I. dipperia n. sp. Comparisons of Isospora dipperia n. sp. with two species of Isospora Schneider, 1881 described in the Americas from birds of the family Sturnidae, related to Cinclidae, revealed that the mean dimensions of the sporulated oöcysts in the new species are considerably smaller than those in I. graculai Bhatia, Chauhan, Arora & Agrawal, 1973from Gracula religiosa (24.6 × 22.4 µm) and I. rothschildi Upton, Wilson, Norton & Greiner, 2001 from Leucopsar rothschildi (22.3 × 21.6 µm). The new species is the first species of Isospora recorded in a bird of the family Cinclidae in the New World.

Optimal sampling design to survey riparian bird populations with low detection probability

ABSTRACT Capsule: Linear censusing and occupancy models based on fixed sampling points are alternative widely used techniques to determine bird densities in riparian ecosystems, although it cannot be always properly executed. Aims: The aim is to assess the survey efficiency for river birds using occupancy models in contexts of impaired visibility owing to dense vegetation along the banks. Methods: We tested whether increasing sampling periods within each survey unit (point) at occupancy models would result in increasing detection probability values. We used two approaches in order to identify the ‘best’ design for White-throated Dippers Cinclus cinclus along forested river stretches: minimizing survey effort of standard single-season site occupancy modelling and exploratory power analysis. Results: With a detection probability of 0.26 (i.e. much lower than in previous studies), a design with 60 sites surveyed 10 min 6 times a year would be the option to survey White-throated Dippers in forested habitats if an acceptable power is required. Simulations further revealed the consistency of the results. Conclusion: We provide guidelines to establish a cost-effective survey design for any long-term monitoring citizen-based programme of a White-throated Dipper population when detection probabilities are low. A strength and novelty of the method is to take advantage of advanced probabilistic approaches (e.g. GRTS) to select the survey sites providing, among other major interests, a spatially balanced geographic coverage.

Territory location and quality, together with climate, affect the timing of breeding in the white-throated dipper

Recent climate change has led to advanced spring phenology in many temperate regions. The phenological response to variation in the local environment, such as the habitat characteristics of the territories birds occupy, is less clear. The aim of this study is to understand how ecological conditions affect breeding time, and its consequences for reproduction, in a white-throated dipper Cinclus cinclus population in a river system in Norway during 34 years (1978–2011). Hatching date advanced almost nine days, indicating a response to higher temperatures and the advanced phenology in the area. Earlier breeding was found in warm springs and at lower altitudes. High population density facilitated earlier breeding close to the coast. Furthermore, when population density was low, breeding was early at territories that were rarely occupied, while in years with high density, breeding was early at territories that were frequently occupied. Also, when population density was low, earlier breeding occurred at territories that on average produced more offspring than other territories, while there was no difference in breeding time in high population years. Selection for early breeding was dependent on spring temperatures and high spring temperatures contributed to higher breeding success during the study period. We found that breeding phenology may have strong effects on fitness in the white-throated dipper, and thus that breeding time is an important ecological factor in a species that feeds mainly on aquatic rather than terrestrial prey.

Troglodytes troglodytes – probable destructor of eggs of Cinclus cinclus

Interspecific or intraspecific destruction of eggs by other small bird species (Passeriformes) is a relatively rare behaviour. It is known from studies of several new world species from families Mimidae and Troglodytidae, but it has never been documented in the Eurasian wren (Troglodytes troglodytes). While studying the breeding biology of the white-throated dipper (Cinclus cinclus) in northern part of Central Slovakia, we documented seven events (frequency 1.8%) when Eurasian wren occupied a dipper’s nest during the breeding season. None of these breeding attempts by the dippers was successful. In all cases, the breeding pairs abandoned their nest. Except of these seven cases, we also found an abandoned nest (situated in the nest box under a bridge) with damaged eggs of the white-throated dipper. According to the intact nest bottom, we hypothesise that the nest was not predated. Here we probably describe the first case of egg destruction by the Eurasian wren in Europe.

Breeding biology and prey availability in the White-throated Dipper in Northern Iberia

Breeding biology and prey availability in the White-throated Dipper in Northern Iberia

The structure and context of male and female song in White-throated Dippers

Female song in birds is more widespread than previously thought but remains poorly studied. Relatively few researchers have compared the structure and function of female song with that of conspecific males, especially in non-duetting species. Here we investigate male and female song in the White-throated Dipper (Cinclus cinclus; hereafter ‘Dipper’), a highly territorial and largely monogamous passerine with a complex song in both sexes. The songs of individually marked birds were recorded over a 3-year period in order to compare the acoustic structure and production of song in males and females at different stages of the breeding cycle. No differences were found in the complexity, frequency or temporal characteristics of male and female songs. However, unpaired males recorded early in the breeding season sang more complex songs than males that were paired up and nest-building or whose breeding attempts were underway, suggesting that male song is used for mate attraction. By contrast, females sang most often during aggressive encounters with birds from outside their territory. Furthermore, males sang throughout the breeding season, when they are highly territorial, whereas females rarely sang after laying had begun. Together, these results support findings from other species that song structure varies with context and suggest that female song in Dippers may be used primarily in mate or territory defence.

Environmental drivers of varying selective optima in a small passerine: A multivariate, multiepisodic approach.

In changing environments, phenotypic traits are shaped by numerous agents of selection. The optimal phenotypic value maximizing the fitness of an individual thus varies through time and space with various environmental covariates. Selection may differ between different life-cycle stages and act on correlated traits inducing changes in the distribution of several traits simultaneously. Despite increasing interests in environmental sensitivity of phenotypic selection, estimating varying selective optima on various traits throughout the life cycle, while considering (a)biotic factors as potential selective agents has remained challenging. Here, we provide a statistical model to measure varying selective optima from longitudinal data. We apply our approach to analyze environmental sensitivity of phenotypic selection on egg-laying date and clutch size throughout the life cycle of a white-throated dipper population. We show the presence of a joint optimal phenotype that varies over the 35-year period, being dependent on altitude and temperature. We also find that optimal laying date is density-dependent, with high population density favoring earlier laying dates. By providing a flexible approach, widely applicable to free-ranging populations for which long-term data on individual phenotypes, fitness, and environmental factors are available, our study improves the understanding of phenotypic selection in varying environments.

Winter territoriality and its implications for the breeding ecology of White-throated Dippers Cinclus cinclus

ABSTRACTCapsule: Pairs of White-throated Dippers Cinclus cinclus which defended winter territories bred earlier than non-territorial individuals, but there was no difference in reproductive success.Aims: The effect of winter territoriality on breeding ecology has rarely been studied in resident birds. We carried out a preliminary investigation of whether winter territorial behaviour and territory size affect the timing of reproduction, breeding territory size and reproductive success in a riverine bird, the White-throated Dipper.Methods: We monitored an individually marked population of White-throated Dippers in the UK. Wintering individuals were classified as either territorial or ‘floaters’ according to their patterns of occurrence and behaviour, and their nesting attempts were closely monitored in the subsequent months. Winter and breeding territory sizes were measured by gently ‘pushing’ birds along the river and recording the point at which they turned back.Results: All birds defending winter territories did so in pairs, but some individuals changed partners before breeding. Territorial pairs that were together throughout the study laid eggs significantly earlier than pairs containing floaters and those comprising territorial birds that changed partners. However, there were no significant differences in clutch size, nestling mass or the number of chicks fledged. There was no relationship between winter territory length and lay date or any measure of reproductive success, although sample sizes were small. Winter territories were found to be significantly shorter than breeding territories.Conclusion: Winter territoriality may be advantageous because breeding earlier increases the likelihood that pairs will raise a second brood, but further study is needed. Territories are shorter in winter as altitudinal migrants from upland streams increase population density on rivers, but this may also reflect seasonal changes in nutritional and energetic demands.

Body Mass Increase before an Oversea Jump in a Short-Distance Migrant, the White-Throated Dipper Cinclus cinclus

A fraction of White-throated Dippers Cinclus cinclus breeding in Scandinavia migrate south over the Baltic Sea during their short-distance migration to the winter quarters. The aim of our study was to investigate patterns of body mass changes between arrival to and departure from the wintering grounds in northern Poland. From a cost-benefit perspective, according to optimal body mass theory, we expected that fuel loading should occur as late as possible before spring migration, to reduce costs associated with high fuel loads. We were interested if sexes (in view of the larger body size of males) and age classes (in view of the less experienced young individuals) differ in the duration of the fueling period and in rates of increase of body mass prior to spring migration. To address these questions, we used morphometric data from 520 Dippers trapped over 16 wintering seasons (1989/1990–2004/2005), including birds trapped more than once (881 captures in total). Body mass was stable between late October and mid February. The period of intensive body mass increase lasted for about one month directly before departure in all Dippers and started in the second half of February. The rate of increase depended on date in a non-linear fashion: the later the date, the higher the rate, with a tendency to stabilize in the last days of March. In late March, the estimated mean body mass was 20–21% higher in males and 18% higher in females compared to the mean body mass during winter. Immature males increased body mass faster than adults (both sexes) and immature females and reached higher body mass prior to departure (increase up to 36%). Fuel loads are not only sufficient to complete the 100–300 km long migration over the Baltic Sea, but probably also to reach breeding destinations in the Scandinavian Mountains, c. 600 km north from the wintering range in northern Poland.

Bird Ringing and Molecular Genetics: Two Complementary Ways for Describing the Movements of White-Throated Dippers Cinclus cinclus

Recovery of ringed birds provides only a partial view of bird movements and may be complemented by using techniques such as molecular analyses. The White-throated Dipper Cinclus cinclus is a passerine restricted to mountain rivers, and considered sedentary in the Iberian Peninsula. The objective of this paper is to establish whether the displacement data found by molecular techniques match those obtained by ringing or not, and to infer if these displacements follow a defined route. 236 Dippers from 13 populations in the Iberian Peninsula were ringed and genotyped using microsatellite markers. The percentage of ringed Dippers that was subsequently recorded outside the sampling area was less than 3%, with most of the birds confined to the same river stretch. However, according to the genetic information presented here, 14.4% of the individuals had moved from their natal localities to other river basins, where they were subsequently trapped. Moreover, migrant Dippers travelled an average distance of 218 km (range 79–484), which is about ten times the distance estimated through ringing recoveries occurring in additional ringing data. The results of the genetic analysis revealed that Iberian Dippers move frequently between mountain ranges and suggest four potential routes for Dipper movements in the Iberian Peninsula. Molecular techniques thus complement the data obtained by ringing and provide new insights into the dispersion of this species.

Song function and territoriality in male and female White-throated Dippers Cinclus cinclus

ABSTRACTCapsule: Male White-throated Dippers Cinclus cinclus are more likely and quicker to respond to the playback of song than females, but both sexes are more likely to respond before the onset of breeding than after.Aims: Territoriality and the function of song in female birds have rarely been studied outside of the tropics or Australasia. We investigated territoriality and song function in males and females of a Northern temperate species, the White-throated Dipper.Methods: We conducted playback trials on established pairs and compared the responses of males and females according to the sex of the simulated intruder and the timing of playback relative to the onset of breeding. A response was classified as movement towards the speaker, singing or both.Results: Males were significantly more likely and quicker to respond to playback than females, but neither sex responded differently to the playback of male and female song. Both sexes were more likely to respond to playback before breeding had begun than after.Conclusions: Our results suggest that both males and females are territorial but that males take the dominant role in defence. Female song appears to elicit a similar response to male song and may play a role in territoriality or mate defence.

Shift in migration phenology of a wintering population of Dippers Cinclus cinclus in northern Sweden

Many organisms have been found to respond to global warming by adjusting one or several aspects of their ecology, such as timing of migration events, time at reproduction and size at maturity. We examined changes in arrival and departure times, and age and sex ratios of overwintering White-throated Dippers Cinclus cinclus in northern Sweden, by comparing data collected in 1975–1979 to a similar dataset from 2010–2014. Between these periods, the average winter temperature had increased by about 2°C. During the latter period the Dippers arrived in their winter area two weeks earlier and departed three weeks earlier. We found no change in age and sex ratios during the study period.