Combining stable isotope analysis and conventional techniques to improve knowledge of the diet of the European Roller Coracias garrulus

Diet studies are crucial for understanding the ecology and evolution of species, as well as for establishing appropriate conservation and management strategies. However, they remain methodologically challenging due to variation between seasons, sites, sexes or age groups and even variation between individuals. Due to method‐specific characteristics and biases, a combination of existing techniques can overcome the inherent limitations of each technique and provide a more accurate and broad picture of species’ food preferences. Here, we examine diet information obtained using three different assessment methods to better understand the trophic ecology of the European Roller Coracias garrulus, a species targeted by conservation measures in Europe. First, we analysed regurgitated pellets and video‐recordings to report the diet composition of adult and nestling Rollers, respectively. Secondly, we used stable isotope analysis (SIA) to investigate adult sexual diet segregation as well as to confirm the main findings regarding adult and nestling diets obtained through conventional methods. Based on the analysis of pellets, the diet of adult Rollers was dominated by Coleoptera, whereas camera images revealed that the diet of nestlings was dominated by Orthoptera, mainly grasshoppers and bush crickets. Blood isotopic signatures of adult and nestling Rollers confirmed the results obtained through pellet and video‐recording techniques. Of the three methods, pellet analysis provided the most comprehensive trophic information regarding the detectable prey spectrum and prey species contribution, as well as basic diet information for the SIA. Our results also highlight the potential of SIA for assessing intraspecific variation in diet by sampling individuals of known age and sex, which is often unfeasible through conventional approaches. SIA analysis showed no differences in δ¹³C and δ¹⁵N ratios of blood between males and females and a high degree of overlap amongst isotopic niches, suggesting no sex‐specific partitioning in resource use. Overall, we showed that the combination of different methods could be used to gain new and clearer insights into avian trophic ecology that are essential for informing habitat management aiming to improve availability of foraging resources.     

The biology of bream, Abramis brama (L), and its natural hybrid with roach, Rutilus rutilus (L), in the River Exe

Hybrids between bream, Abramis brama , and roach, Rutilus rutilus , occur in the lower reaches of the River Exe and were positively identified by their meristic features and shape of the pharyngeal bone. The growth of bream and hybrids was determined by back-calculation from scales. Annual checks were laid down in early June. The mean length for age of female bream was significantly larger than that of males for fish 6 years of age and older. This divergence in growth rate was associated with the sexual maturation of the fish. Data for the sexes were combined and compared with the growth rate of hybrids and roach from the same region. Hybrid growth was similar to that of bream for the first 6 years of life but was intermediate between that of the two parent species in the older age groups. Some hybrids with developing gonads were found. A change in the diet of bream from planktonic feeding to a benthophagic habit with age was noted. Detritus, substrate and chironomid larvae formed the bulk of the diet of hybrids.     

Does testosterone mediate the trade-off between nestling begging and growth in the canary (Serinus canaria)?

Nestling birds solicit food from their parents with vigorous begging displays, involving posturing, jostling and calling. In some species, such as canaries, begging is especially costly because it causes a trade off against nestling growth. Fitness costs of begging like this are predicted by evolutionary theory because they function to resolve conflicts of interest within the family over the provision of parental investment. However, the mechanism that links these costs with nestling behaviour remains unclear. In the present study, we determine if the relationships between nestling androgen levels, nestling begging intensities and nestling growth rates are consistent with the hypothesis that testosterone is responsible for the trade-off between begging and growth. We test this idea with a correlational study, using fecal androgens as a non-invasive method for assaying nestling androgen levels. Our results show that fecal androgen levels are positively correlated with nestling begging intensity, and reveal marked family differences in each trait. Furthermore, changes in fecal androgen levels between 5 and 8 days after hatching are positively associated with changes in nestling begging intensity, and negatively associated with nestling growth during this time. Although these correlational results support our predictions, we suggest that that experimental manipulations are now required to test the direct or indirect role of testosterone in mediating the trade-off between begging and growth.     

Local weather conditions have complex effects on the growth of blue tit nestlings

Adverse weather conditions are expected to result in impaired nestling development in birds, but empirical studies have provided equivocal support for such a relationship. This may be because the negative effects of adverse weather conditions are masked by parental effects. Globally, ambient temperatures, rainfall levels and wind speeds are all expected to increase in a changing climate and so there is a need for a better understanding of the relationship between weather conditions and nestling growth. Here, we describe a correlative study that examined the relationships between local temperatures, rainfall levels and wind speeds and the growth of individual blue tit (Cyanistes caeruleus) nestlings in relation to their hatching order and sex. We found that changes in a range of morphological characters were negatively related to both temperature and wind speed, but positively related to rainfall. These patterns were further influenced by the hatching order of the nestlings but not by nestling sex. This suggests that the predicted changes in local weather conditions may have complex effects on nestling growth, but that parents may be able to mitigate the adverse effects via adaptive parental effects. We therefore conclude that local weather conditions have complex effects on avian growth and the implications for patterns of avian growth in a changing climate are discussed.     

Reproductive success and nestling diet in the Lesser Spotted Woodpecker ( Picoides minor ): the early bird gets the caterpillar

Populations of Lesser Spotted Woodpecker (Picoides minor) are decreasing in size, necessitating management strategies. However, data on the reproductive biology of this species are scarce. The aim of this study was to investigate the influence of timing of breeding and nestling diet on the reproductive success of the Lesser Spotted Woodpecker and thereby contribute to an understanding of the determinants influencing its reproductive success. During 6 study years between 1996–2003, we investigated various variables of reproductive success in a Lesser Spotted Woodpecker population in the Taunus low mountain range, Germany. We observed nestling feeding at breeding holes to assess the composition of nestling diet and how it changes during the season. Clutch size, number of fledglings as well as body mass of the nestlings declined with the start of egg laying. Pairs composed of individuals that had breed together in previous years started egg laying earlier than newly established pairs. Nestling diet consisted mainly of aphids, caterpillars, craneflies and wood-living larvae. The composition changed considerably within the breeding season in both early and late broods. However, early broods were provided with caterpillars more frequently, whereas late broods received wood-dwelling larvae more often. Our results suggest that Lesser Spotted Woodpeckers time their breeding so as to coincide with the early nestling stage with the highest availability of caterpillars, since this is the time of highest energy demand. Moreover, food availability declines during the breeding season, and the decline in reproductive performance seems to be an effect of this development.     

Low cytochrome b variation in bream Abramis brama

Variability in cytochrome b (cytb) in European populations of bream Abramis brama was assessed. The cytb gene was found to be strongly conserved in A. brama relative to other cyprinid taxa. This limits the usefulness of this marker in examining geographical genetic structure in this species and raises interesting questions as to the recent evolutionary history of the species.     

DIFFERENTIAL GROWTH AND BODY COMPOSITION IN ALTRICIAL PASSERINES

The differential development of various body organs and of fat, water, and other constituents was studied in three species with altricial nestlings—Blue Tit, House Martin and House Sparrow.
In all species resources available at each stage of the nestling period were allocated to those components of most use to the nestlings at the time, although due regard was paid to future needs. Components associated with the ingestion and assimilation of food, such as the mouth, gizzard, intestine and liver, developed early in the nestling period whilst locomotory components, such as wings and pectoral muscles, developed late. Similarly, body plumage needed for insulation developed ahead of the locomotory remiges and rectrices, but only after much of the nestlings' growth in size had been completed.
The water index (water content/lean dry weight) provided a consistent index of tissue and nestling maturity amongst young of different nutritional status. This index was very similar for all three species when age was expressed as a fraction of the nestling period.
Both absolute fat content and the fat index (fat content/lean dry weight) increased with age. The adaptive value of these trends and of interspecific differences in fat index is discussed.
The results are seen as consistent with both the physiological bottleneck models of avian growth rates. It is suggested that the growth patterns of birds may be dominated more by ecological considerations affecting all aspects of the development mode than by internal physiological constraints affecting growth rates alone.     

Chick development in free-living great tits Parus major in relation to calcium availability and egg composition

Evidence from a number of avian studies suggests that limitation of exogenous calcium (Ca) may reduce egg quality and retard nestling growth. However, it is poorly understood whether reduction in chick growth in Ca-poor areas is due to insufficient intake of dietary Ca or caused by maternal Ca limitation mediated through subtle changes in composition of eggs. In this study, we provide new evidence that Ca availability during egg formation may indeed affect egg composition and influence chick development of the great tit Parus major at early developmental stages. Ca-supplemented birds breeding in base-poor pine forests produced eggs with elevated yolk Ca concentration compared with controls, while no such effect of supplementation was detected in case of eggshell thickness. Nestling tarsus length in the first half of the nestling period was positively influenced by both yolk dry mass and yolk Ca concentration. The effect of supplementary Ca did not persist throughout the nestling period; initial effects of egg components disappeared as nestlings aged. We conclude that apparently normal eggs may harbor poor nutrient and mineral conditions for chick growth. Such subtle changes in composition of eggs can depress chick growth, especially in harsh years.     

Hybrids of Abramis brama with Scardinius erythrophthalmus and Rutilus rutilus from Lake Volvi, Macedonia, Greece

Two specimens of the hybrid Abramis brama × Scardinius erythrophthalmus and a single specimen of the hybrid A. brama × Rutilus rutilus are reported and described from Lake Volvi, Macedonia, Greece. This is the first occurrence of either hybrid in Greek fresh waters.     

RAPD fingerprinting of common bream Abramis brama L., roach Rutilus rutilus L., and their F1 hybrids

The polymerase chain reaction with arbitrary primers (RAPD-PCR) was used to study and to evaluate the genetic variation in the hybrid progeny of two Cyprinidae species, common bream Abramis brama and roach Rutilus rutilus. Genetic polymorphism was studied in 20 fishes (young of the current year) obtained in four individual crosses: R. rutilus x R. rutilus (RR), A. brama x A. brama (AA), R. rutilus x A. brama (RA), and A. brama x R. rutilus (AR). Amplification spectra obtained with eight primers contained 288 fragments, 97.6% of which proved to be polymorphic. The proportion of polymorphic fragments was 75.0% in the RR progeny, 58.1% in the AA progeny, 84.9% in the AR progeny, and 77.8% in the RA progeny. Classification analysis in the space of principal components was performed with the first four components, which together accounted for 64% of the total variance of the character under study. The individual contributions of components I, II, III, and IV were 26.8, 16.8, 11.5, and 8.9%, respectively. Fishes of the two pure species and the hybrid progeny (direct and reverse hybrids together) were clearly differentiated in the space of principal components I and II. The best differentiation of the four samples (RR, AA, RA, and AR) was observed in the space of principal components II and IV. Possible causes of high genetic variation in interspecific hybrids are discussed.     

Pectoral fin ray aging: an evaluation of a non-lethal method for aging gars and its application to a population of the threatened Spotted Gar

Spotted Gar (Lepisosteus oculatus), a species listed as Threatened under the Canadian Species at Risk Act (SARA) was collected during May and June, 2007 from several sites in Rondeau Bay, a shallow coastal wetland of Lake Erie. The first pectoral fin ray was removed from 78 individuals to age the fish and to determine individual growth characteristics. To assess the validity of using pectoral rays to age Spotted Gar, we compared techniques (otoliths, branchiostegal rays and pectoral rays) for ten individuals captured in southwestern Michigan. Agreement between readers and amongst the three structures was high; thus aging of Spotted Gar using sectioned pectoral rays is an effective method. Rondeau Bay specimens varied in age from 3 to 10 years and from 515 to 761 mm total length. Regression analysis of length vs. age data was calculated to be $ {\hbox{y}} = {19}.{\hbox{217x}} + {491}.{19}\left( {{{\hbox{R}}^{{2}}} = 0.{22}} \right) $ . The low R ² value is attributed to having males and females, which differ in growth rates, combined. Growth rates of Rondeau Bay specimens were compared to a Louisiana population using ANCOVA. No significant difference was found in the rate of growth between these populations; however, condition was low as compared to a standard weight equation. This may lead to lower fecundity, contributing to the species?? rarity in Canada.     

When assumptions on visual system evolution matter: nestling colouration and parental visual performance in birds

Comparative studies in visual ecology of birds often rely on several assumptions on the evolution of avian vision. In this study, we show that when these assumptions are not upheld, conclusions may be strongly affected. To illustrate this purpose, we reanalysed the data of Avilés & Soler (J. Evol. Biol. 22 : 376–386, 2009) who demonstrated that nestling gape colouration in altricial birds is associated with visual system. We show that a slight change in analysis methodology leads to opposite conclusions. Such conflicting result raises the problem of applying powerful methods developed for continuous variables to a small sample and a small number of independent events of qualitative visual system shift in comparative analyses. Further, we show that the current trend to assume strong phylogenetic inertia of avian visual systems is contradicted by data and that the sequencing of the SWS1 opsin gene should be considered as an alternative approach.     

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.     

四川南充市区珠颈斑鸠的繁殖生态学和巢址选择

2002年11月~2004年4月在四川省南充市区内对珠颈斑鸠(Streptopelia chinensis)繁殖生态和巢址选择进行了研究。结果表明:珠颈斑鸠3月初开始求偶交配,求偶行为复杂,有“婚飞”行为;雌雄参与筑巢,营巢期7~8 d。影响巢址选择的主要因素有6种:栖位与巢周隐蔽因子、巢下隐蔽因子、光照因子、人为活动因子、食物因子和营巢树因子;窝卵数2枚,雌雄轮流孵卵,孵卵期17~18 d,孵化率86.67%;雌雄均参与育雏,育雏期18~20 d,雏离巢率73.08%,繁殖生产力1.82,种群育雏高峰期为7月和8月中上旬。     

PCR-DGGE技术在细菌多样性研究中的条件优化

基于聚合酶链式反应的变性梯度凝胶电泳（Polymerase chain reaction denaturing gradient gel electrophoresis,PCR-DGGE）技术作为研究微生物物种多样性和动态变化的分子检测工具之一,具有可靠性强、重复性好、方便快捷等优点。该技术无需传统的微生物分离培养,便能快速、准确地获取复杂样品中微生物的菌群多样性、动态性及其功能菌的遗传信息,被广泛用于环境生态学的研究中。该文概述了PCR-DGGE技术的基本原理,并对该技术的各个环节如DNA提取、PCR扩增、DGGE条件以及图谱染色等条件的优化进行探讨,提出可能出现的影响因素,并对该技术自身存在的局限性和应用前景进行了评价。     

Incubation temperature affects growth and energy metabolism in blue tit nestlings

Because the maintenance of proper developmental temperatures during avian incubation is costly to parents, embryos of many species experience pronounced variation in incubation temperature. However, the effects of such temperature variation on nestling development remain relatively unexplored. To investigate this, we artificially incubated wild blue tit (Cyanistes caeruleus L.) clutches at 35.0°, 36.5°, or 38.0°C for two-thirds of the incubation period. We returned clutches to their original nests before hatching and subsequently recorded nestling growth and resting metabolic rate. The length of the incubation period decreased with temperature, whereas hatching success increased. Nestlings from the lowest incubation temperature group had shorter tarsus lengths at 2 weeks of age, but body mass and wing length were not affected by temperature. In addition, nestlings from the lowest temperature group had a significantly higher resting metabolic rate compared with mid- and high-temperature nestlings, which may partly explain observed size differences between the groups. These findings suggest that nest microclimate can influence nestling phenotype, but whether observed differences carry over to later life-history stages remains unknown.     

The effect of ligula intestinalis on some lipid exchange indexes of the spleen of the host, bream abramis brama of different age

The results of the comparative analysis of the spleen in healthy individuals of bream Abramis brama and those infected by the Ligula intestinalis plerocercoids are given. Two age groups of bream were studied. The comparison was carried out by the index of common lipids (CL), the content of common lipids, the intensity of lipid peroxidation (POL), and the common antioxidant activity (CAA). The dependence of the lipid exchange character in the fishes infected by Ligula on age, as well as on different levels of the infestation is demonstrated.     

When will rejection of parasite nestlings by hosts of nonevicting avian brood parasites be favored? A misimprinting-equilibrium model

It has been suggested that discrimination and rejection of thenestlings of avian brood parasites are most likely to evolvewhen the parasite nestling is raised alongside the host nestlings,for example, many cowbird-host systems. Under these circumstances,the benefits of discrimination are high because the host parentsmay save most of their brood. However, there is a general absenceof nestling rejection behavior among hosts of nonevicting parasites.In a cost-benefit equilibrium model, based on the premise thathost species learn to recognize their offspring through imprintingon first breeding, we show that nestling recognition can beadaptive for hosts of cowbirds, but only under strict conditions.Namely, when host nestling survival alongside the parasite islow, rates of parasitism are high and the average clutch sizeis large. All of these conditions are seldom simultaneouslyachieved in real systems. Most importantly, the parasite nestling,on average, does not sufficiently depress host nestling survivalto outweigh the costs of nestling recognition and rejectionerrors. Thus, we argue that nestling acceptance behaviors byhosts of nonevicting brood parasites may be explained as anevolutionary equilibrium in which recognition costs act as astabilizing selection pressure against rejection when most ofthe host's offspring survive parasitism.     

Long-term changes in the parasite fauna of the bream Abramis brama L. in eutrophicated lake

Data on the dynamics of parasite fauna if the bream Abramis brama for 50-year period are presented. The relation between trophic status of the reservoir, preferred type of the bream feeding, and the abundance of its parasites is shown. It was established, that the number of parasites developing in plankton organisms increases during the period of intensive eutrophication. Recent data on the parasite fauna of bream indicate preferred feeding of the host on benthic invertebrates, that is favourable to its growth. Permanent tendency to the increase of the bream invasion by the Diplostomum metacercaria could be a reliable parasitological indicator of the water body eutrophication.     

Population Dynamics of the Bream Abramis brama in Lake Peipus

Journal of Ichthyology - Population dynamics of the bream Abramis brama in lakes Peipsi and Pihkva for the period from 1980 to 2009 has been studied by means of cohort models. Bream stock increased...