Variable energetic responses to clutch size manipulations in white-throated dippers Cinclus cinclus

We used the doubly-labelled water technique to measure daily energy expenditure (DEE) of a free-living uniparental incubator, the white-throated dipper Cinclus cinclus , in Scotland. DEE was 205±8 (s.e.m.) kJ d⁻¹ for 17 females incubating their natural clutch sizes, equivalent to 3.2±0.1×basal metabolic rate (BMR). To investigate the influence of clutch size on the energy budget, we measured the DEE of 14 females with clutches increased or reduced by a single egg. Birds with reduced clutch sizes had an energy expenditure with a mean and variance that did not differ from those of birds with unmanipulated clutches. Enlarging the clutch led to an increase in energy expenditure to over 4×BMR for some individuals but not for others, resulting in greater variance in energy expenditure for birds with enlarged clutches. Individual variation in energy expenditure could not be fully explained by environmental conditions, by patterns of behaviour or clutch size. Incubating females received a maximum of only 4 kJ d⁻¹ (2% of DEE) from provisioning by the male, and mobilised up to 6 kJ d⁻¹ (3% of DEE) from reserves. Females spent 2.9±0.2 h (n=20) away from the nest each day, so a foraging rate of 95 kJ h⁻¹ was required during incubation recesses to balance DEE. This 'required foraging rate' is double previous estimates of the maximum rates of energy acquisition for birds of this size. We suggest that the greater likelihood of a raised energy expenditure associated with larger clutches, combined with the difficulties in maintaining energy supplies, may constitute a constraint on avian clutch size.     

Extrapair paternity and genetic diversity: the white‐throated dipper Cinclus cinclus

Passerine bird species vary considerably in the frequency of extrapair paternity, but the factors causing this variation are not well understood. There is some comparative evidence that extrapair paternity is associated with the population level of genetic diversity, but there is no consensus of how genetic diversity should be measured and compared across species or populations. Here we report a low frequency of extrapair paternity (2% extrapair offspring) in a Norwegian population of the white‐throated dipper Cinclus cinclus, which shows strong signs of reduced genetic diversity. We encountered difficulties in constructing a robust parentage analysis system for the species, largely due to consistently low polymorphism levels in 100 heterologous microsatellite markers. Furthermore, single‐nucleotide polymorphisms (SNPs) were almost absent in intron sequences in 10 nuclear genes (>5 kb) that are much more polymorphic in other species. Hence, our results seem consistent with the genetic diversity hypothesis that predicts a low frequency of extrapair paternity in species with low genetic diversity. Heterologous microsatellite markers are generally unsuitable for interspecific comparisons of genetic diversity as they show strong phylogenetic dependency in polymorphism levels. We suggest that SNP rates at homologous nuclear introns, like those presented here, can provide a useful method for obtaining unbiased estimates of genome‐wide genetic diversity across populations and species.     

The reproductive success of the dipper Cinclus cinclus in relation to the acidity of streams in south-west Scotland

1. The breeding success of dippers Cinclus cinclus was assessed in south-west Scotland over 3 years and related to the acidity of the streams along which they bred. 2. At sites of high acidity, clutch and brood sizes were significantly smaller than those at sites of lower acidity. 3. Egg weight and the incidence of second clutches increased significantly with pH, but there was no evidence to suggest an effect of acidity on hatching success. 4. The rate at which food was delivered to individual nestlings was significantly lower at acidic than non-acidic sites. Nestling weights and survival were lower at more acidic sites. 5. Reduced brood sizes, low nestling survival and the low incidence of second brooding attempts resulted in a significant reduction in total productivity (number of fledglings produced, per pair, per year) at acidic compared with non-acidic streams. 6. It is suggested that pH-related differences in the invertebrate fauna of streams result in low prey availability for dippers on acidic streams, leading to reduced productivity.     

Evidence of a highly complex phylogeographic structure on a specialist river bird species, the dipper (Cinclus cinclus)

This study details the phylogeographic pattern of the white-throated dipper (Cinclus cinclus), a Palearctic, temperate, passerine bird that is exclusively associated with flowing water. Our results reveal a complex phylogeographic structure with at least five distinct lineages for the Western Palearctic region. As for many species of the Western Palearctic fauna and flora, this genetic structure is probably linked to the isolation of populations in different southern refuges during glacial periods. Furthermore, the isolation of populations in Scandinavia and/or Eastern regions, but also in Morocco and probably in Corsica, was accentuated by ecological and biogeographic barriers during Quaternary interglacial periods. During glacial periods, Italy, Sicily and the Balkano-Carpathian region acted as major refuge zones for the dipper. At the end of the last ice age, Western Europe was repopulated by dippers from an Italian refuge, while Eastern Europe was recolonised by Balkano-Carpathian birds. A large contact zone between these two lineages was evidenced and extends from Luxembourg to Hungary. Finally, our results indicate the need to clarify the taxonomic status of the dipper, especially concerning the European subspecies whose validity appears uncertain.     

Exploitation of prey by a river bird, the dipper Cinclus cinclus (L.), along acidic and circumneutral streams in upland Wales

SUMMARY. 1. The diet of the Eurasian dipper Cinclus cinclus. a riverine bird from a globally widespread genus, was assessed through all stages of its annual cycle using published data and field studies from streams of contrasting chemistry. Time-activity budgets were also compiled throughout the year and used to estimate annual energy requirements from the stream ecosystem. 2. The annual energy requirements for a territorial pair ranged from 148,000 to 158,000 kJ yr^?1 depending on whether one or two broods were reared. After allowing for assimilation efficiency, these requirements were estimated to represent 10.5–11.0 kg dry mass of fish and invertebrates. Using representative values for territory size (4680–11,250 m²), annual exploitation of secondary production was estimated at 0.93–2.35 g dry mass m^?2. 3. Several features combined to focus the predatory load on certain organisms over different stages of the annual cycle. These included the availability and selection of alternative prey, the need to provision nestlings with large items such as trichopteran larvae, and the use by females of calcium-rich prey such as fish prior to egg formation. 4. Across their range of territory size, annual exploitation (dry mass) by dippers was estimated at 0.06–0.29 g m^?2 for Plecoptera. 0.02–0.22 g m^?2 for Ephemeroptera. 0.59–1.11 g m^?2 for Trichoptera and 0–0.78 g m^?2 for fish. Exploitation of Ephemeroptera. I richoptera and fish were all highest in circumneutral streams, but exploitation of Plecoptera was highest in acidic streams because other prey were scarce. 5. Cottids dominated the fish component of the diet. Influences on their density could be substantial according to available data on production in Welsh streams. Hydropsychids and limnephilids dominated the trichopteran component, with exploitation again representing potentially substantial amounts of production. Contemporaneous data are required on benthic production and exploitation by the birds. 6. The ecological role of birds in rivers particularly, and aquatic ecosystems generally, is currently neglected but worthy of considerable research effort.     

The diet of breeding dippers Cinclus cinclus cinclus and their nestlings in southwestern Norway

The diet of dippers in south west Norway was investigated by faecal analysis during the 1985 breeding season. Overall, the diets of adults and nestlings were similar and consisted mostly of nymphs and larvae of Baetidae (mayflies). Leuctridae/Nemouridae (stoneflies). Hydropsychidae, Limnephilidae and Rhyaeophilidae (caddisflies). However, strong trends were apparent with nestling age: large items such as caddisflies declined in adult diet but increased in nestling diet as the chicks grew. The pattern probably reflected the growing energy demands of the brood in a central-place. Because some of the items of dietary importance are scarce in acidic streams, we stress the need for research on the influences of acidification on the ecology of Scandinavian dippers.     

The adaptive significance of brood size and time of breeding in the dipper Cinclus cinclus (Aves: Passeriformes) as seen from post-fledging survival

We assessed the post-fledging survival of dippers Cinclus cinclus from 743 broods in relation to brood size, time of hatching and territory quality. We paid particular attention to assessing whether contrasting breeding performance along unproductive (i.e. acidic) and productive (i.e. circumneutral) rivers represented strategies which optimized the number of surviving young.
For all brood sizes, post-fledging survival varied significantly through the breeding season, with most survivors coming from attempts in the peak period of hatching. After correcting for these seasonal effects, the most common brood size overall, of four, was also the most productive as seen from post-fledging survival; differences in the frequency of occurrence and survival between broods of four and five were marginal. Moreover, a change in the modal brood size from five to four occurred as the season progressed. consistent with a shift in brood productivity.
Broods at acidic sites were significantly smaller than at circumneutral sites; while brood size four was the most productive at both types of site, brood size three was the second most productive at acidic sites, while brood size five was the second most productive at circumneutral sites. Dippers at acidic sites bred significantly later than at circumneutral sites, but post-fledging survival declined most rapidly through the season at the former.
These survival data provide evidence from both seasonal and spatial patterns that brood sizes in the dipper may be optimized in ways consistent with the enhancement of productivity. By contrast, delayed breeding at acidic sites contrasted with the patterns expected from optimization, instead reflecting resource scarcity.     

Phylogeography of the white-throated dipper Cinclus cinclus in Europe

Cytochrome b gene sequence variation (902 bp) was used to investigate phylogenetic relationships and genetic differentiation among the four subspecies of European white-throated dipper Cinclus cinclus (Aves; Cinclidae). Six cytochrome b haplotypes were revealed, the most common one (H 13–4) was shared by all seven populations studied. Central European C. c. aquaticus was genetically more diverse than the other subspecies (although not significantly so, due to small sample sizes), whereas our sample of the nominate subspecies from the French Pyrenees showed no haplotype variation. Pairwise comparisons of the four subspecies showed significant genetic differentiation between the taxa except for a lack of differentiation of C. c. hibernicus versus C. c. aquaticus and C. c. cinclus. The genetic structure and the phylogeographic pattern were not related to the geographic distribution of the four subspecies thus disputing the validity of the current infraspecific taxonomy of C. cinclus at least in Europe.Béatrice Lauga and Christine Cagnon contributed equally to this paper.     

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

Capsule: 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.     

A description of Cinclotaenia georgievi n. sp. (Cestoda: Dilepididae), a tapeworm from the dipper Cinclus cinclus (L.) (Passeriformes: Cinclidae)

Cinclotaenia sp., described originally by Georgiev & Genov (1985) from the dipper Cinclus cinclus (L.) in Bulgaria, has recently been identified from the same host in the Carpathian Mountains in the Slovak Republic. This tapeworm is considered to be a new species, which is named C. georgievi n. sp. It is characterised by: a scolex armed with 23-27 (predominantly 24-26) hooks in two rows; hooks 30.5-36 microm long, with a blade 10-13.5 microm long and resembling in shape the diorchoid hooks of hymenolepidids; irregularly alternating genital pores with simple genital atria; a slightly conical cirrus armed by small spines of up to 3 microm in length; 24-51 testes posterior to a bi-alate, branched ovary; a gravid uterus filled with egg packets; and eggs with filaments. C. georgievi n. sp. differs from the closely-related C. tarnogradskii (Dinnik, 1927) in the slightly higher number of rostellar hooks, which have longer blades, and a larger cirrus.     

Breeding territory fidelity in a partial migrant, the American dipper Cinclus mexicanus

American dipper Cinclus mexicanus populations are frequently composed of resident individuals that occupy permanent territories year round and migratory individuals that overwinter with residents but migrate to breeding territories on higher elevation creeks each spring. Between 1999 and 2004 we examined how migratory strategy (resident/migratory) and sex differences influence breeding territory fidelity of American dippers occupying the Chilliwack River watershed, British Columbia, Canada. Counter to expectation we found that the migratory strategy of American dippers did not influence whether birds breeding in one year were found on their former breeding territory in the next. Migratory strategy also did not affect the probability that known surviving dippers occupied the same breeding territory in the following year. Males and females were equally likely to be found on their former territory in the following year (females 43%, males 41%) and known survivors had similar levels of breeding territory fidelity (females 74%, males 68%). However, breeding territory fidelity of males and females varied in response to different factors. Surviving female dippers were more likely to be found on their former breeding territory in the subsequent year following a successful breeding attempt than an unsuccessful breeding attempt. Prior reproductive performance did not influence whether surviving male dippers were found on their former breeding territory. Male dippers were more likely to be found on their former territory and, if they survived, have higher breeding territory fidelity when their mate also returned to that same territory. Mate retention also influenced whether females were found on their former territory in the following year but had no effect on the breeding territory fidelity of known survivors. We argue that sex‐specific dispersal decision rules in American dippers are driven by sex differences in the predictability of breeding performance between years and sex differences in how mate retention influences subsequent reproductive success.     

Timing of onset of breeding in three different Dipper Cinclus cinclus populations in France

Capsule Timing of breeding varies widely.     

On the ecology of wintering Dippers(Cinclus cinclus) in northern Sweden

Summary Wintering Dippers were studied in the coastal region of the province Västerbotten in northern Sweden with special emphasis on winter movements, winter site-tenacity and population dynamics. In three different streams the number of wintering Dippers varied markedly during the winter, with maximum numbers in mid-winter (December–January). Sex and age ratio also varied during the winter. and adult birds outnumbered and juvenile birds during most of the winter. The wintering Dippers showed a good site-tenacity and about 17 % of the birds returned to the same stream the following season. Two long-distance recoveries and one control of a Dipper banded in Finland might indicate the origin of the wintering Dippers as well as the migratory routes of the species in northern Scandinavia, all in consistence with earlier studies of the migration of the species. Body-weight and wing-length data corresponded well with earlier investigations in southern Scandinavia.It is suggested that the structure of the wintering Dipper population can be explained by a mechanism of dominance-influenced migration proposed byGauthreaux (1978).

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Zur Winterökologie der Wasseramsel(Cinclus cinclus) in Nordschweden

Zusammenfassung 1975–1979 wurden Wasseramseln in drei verschiedenen Flüssen im Küstenbereich der Provinz Västerbotten untersucht unter besonderer Berücksichtigung der Wanderungen, Ortstreue und Populationsstruktur im Winter.Die Anzahl der Wasseramseln zeigte klare jahreszeitliche Unterschiede mit einem Maximum in den Monaten Dezember und Januar. Die Geschlechter- und Altersverteilungen variierten deutlich während des Winters; und Altvögel überwogen vor allem am Ende des Winters gegenüber und Jungvögeln. Die überwinterten Wasseramseln zeigten eine ausgeprägte Ortstreue; ca. 17 % der Vögel kehrten im folgenden Jahre zu den gleichen Flüssen zurück.Zwei Wiederfunde von Wasseramseln, die im Untersuchungsgebiet beringt worden waren, aus Norwegen und eine Kontrolle aus Finnland deuten auf Herkunft und Zugwege der in Nordschweden überwinternden Wasseramseln hin. Diese Wiederfunde stimmen mit den Untersuchungen vonAndersson &Wester (1976) überein.Die Körpergewichte und Flügellängen zeigten gute Übereinstimmung mit Untersuchungen in Südschweden (Andersson &Wester 1971, 1972).Es wird vorgeschlagen, die Populationsstruktur überwinternder Wasseramseln anhand eines Modells der dominance-influenced migration (Gauthreaux 1978) zu erklären.

     

Aspects of the breeding biology of Dippers Cinclus cinclus in the southern catchment of the River Wye,Wales

Laying dates, clutch and brood size, and the incidence of double brooding, in Dippers breeding in the southern catchment of the Welsh River Wye between 1978 and 1983 are described and compared with data from other regions of Britain and mainland Europe. The mean size of 222 clutches (4.78±0.08) was found to be significantly larger than values given by all other studies in Britain where data were sufficient for statistical comparison. This is discussed in relation to territory quality and other influences.     

Factors influencing the abundance of breeding Dippers Cinclus cinclus in the catchment of the River Wye, mid-Wales

The number of breeding Dippers was assessed in relation to environmental features and benthic macro-invertebrates over 220 km of tributaries in or adjacent to the catchment of the Welsh River Wye in 1982. Bivariate regression and multivariate analysis revealed strong correlations between breeding abundance and combinations of variables describing stream-gradient and the relative abundances of larval Trichoptera and nymphal Plecoptera. The results are discussed in relation to aspects of the feeding ecology of breeding Dippers and their nestlings.     

Time-activity budgets and energetics of Dipper Cinclus cinclus are dictated by temporal variability of river flow.

The white-throated Dipper (Cinclus cinclus) is unique among passerine birds by its reliance on diving to achieve energy gain in fast-flowing waters. Consequently, it should have evolved behavioural adaptations allowing responding directly to runoff patterns (one of the assumptions of the Natural Flow Regime Paradigm-NRFP). In this study (October 1998-August 2001), we investigated how behavioural and energy use strategies in Dippers might vary under the natural flow regime of snowmelt-dominated streams in The Pyrénées (France) where natural flow regime is highly seasonal and predictable. We recorded time spent in each of 5 behavioural activities of ringed birds to estimate time-activity budgets and derive time-energy budgets enabling the modelling of daily energy expenditure (DEE). Annual pattern in 'foraging' and 'resting' matched perfectly the annual pattern of the natural regime flow and there was a subtle relationship between water stage and time spent 'diving' the later increasing with rising discharge up to a point where it fell back. Thus, time-activity budgets meet the main prediction of the NRFP. For males and females Dippers, estimates of feeding rates (ratio E(obs)/E(req)=observed rate of energy gain/required foraging rate) and energy stress (M=DEE/Basal Metabolic Rate) also partly matched the NFRP. Maximum value for the ratio E(obs)/E(req) was registered in May whilst M peaked in spring. These ratios indicated that Pyrenean Dippers could face high energy stress during winter but paradoxically none during high snowmelt spates when food is expected to be difficult to obtain in the channel and when individual birds were observed spending ca 75% of the day 'resting'. Annual pattern in DEE did not match the NFRP; two phases were clearly identified, the first between January to June (with oscillating values 240-280 kJ d(-1) ind(-1)) and the second between July and December (200-220 kJ d(-1) ind(-1)). As total energy expenditure was higher during the most constraining season or life cycle, we suggest that energy management by Dippers in Pyrenean mountain streams may fit the 'peak total demand' hypothesis. At this step of the study, it is not possible to tell whether Dippers use an 'energy-minimisation' or an 'energy-maximisation' strategy.     

Time-activity budgets and energetics of Dipper Cinclus cinclus are dictated by temporal variability of river flow

The white-throated Dipper (Cinclus cinclus) is unique among passerine birds by its reliance on diving to achieve energy gain in fast-flowing waters. Consequently, it should have evolved behavioural adaptations allowing responding directly to runoff patterns (one of the assumptions of the Natural Flow Regime Paradigm—NRFP). In this study (October 1998–August 2001), we investigated how behavioural and energy use strategies in Dippers might vary under the natural flow regime of snowmelt-dominated streams in The Pyrénées (France) where natural flow regime is highly seasonal and predictable. We recorded time spent in each of 5 behavioural activities of ringed birds to estimate time–activity budgets and derive time–energy budgets enabling the modelling of daily energy expenditure (DEE). Annual pattern in ‘foraging’ and ‘resting’ matched perfectly the annual pattern of the natural regime flow and there was a subtle relationship between water stage and time spent ‘diving’ the later increasing with rising discharge up to a point where it fell back. Thus, time–activity budgets meet the main prediction of the NRFP. For males and females Dippers, estimates of feeding rates (ratio E_obs/E_req = observed rate of energy gain / required foraging rate) and energy stress (M = DEE / Basal Metabolic Rate) also partly matched the NFRP. Maximum value for the ratio E_obs/E_req was registered in May whilst M peaked in spring. These ratios indicated that Pyrenean Dippers could face high energy stress during winter but paradoxically none during high snowmelt spates when food is expected to be difficult to obtain in the channel and when individual birds were observed spending ca 75% of the day ‘resting’. Annual pattern in DEE did not match the NFRP ; two phases were clearly identified, the first between January to June (with oscillating values 240–280 kJ d^− 1 ind^− 1) and the second between July and December (200–220 kJ d^− 1 ind^− 1). As total energy expenditure was higher during the most constraining season or life cycle, we suggest that energy management by Dippers in Pyrenean mountain streams may fit the ‘peak total demand’ hypothesis. At this step of the study, it is not possible to tell whether Dippers use an ‘energy-minimisation’ or an ‘energy-maximisation' strategy.     

Diet of Dippers Cinclus cinclus during an early winter spate and the possible implications for Dipper populations subjected to climate change

The prey composition of the diet of Dippers Cinclus cinclus was shown to differ between baseflow and spate conditions. In southwest Ireland, faecal pellets were collected during a heavy spate in early winter 1991 and during a period of baseflow conditions three weeks later. The diet composition differed significantly between the two periods. During baseflow conditions diet was dominated by trichopteran larvae, especially Limnephilidae, whereas during the spate period diet was composed primarily of ephemeropteran nymphs, particularly Baetidae, and dipteran larvae of the family Simuliidae. Diet during the spate period also contained greater proportions of prey taxa of terrestrial origin. Enhanced hydrological cycles with greater precipitation, predicted under current climate change models, may have an effect on the diet of Dippers and this is discussed.