Divergent character displacement in the song of two allospecies: the Pied Flycatcher Ficedula hypoleuca, and the Collared Flycatcher Ficedula albicollis

Songs of the three flycatcher forms, Ficedula hypoleuca hypoleuca, Ficedula albicollis albicollis and Ficedula albicollis semitorquata , were distinguishable from one another using a multivariate analysis. F. albicollis semitorquata , which has an intermediate song character, is considered to be a primary allopatric form while the nominate subspecies of albicollis is assumed to be dispersed into sympatry with F. h. hypoleuca . The differences in song between the nominate albicollis and F. hypoleuca are accentuated in their zone of sympatry and are mostly due to divergence in the albicollis song. The song is primarily an epigamic vocalization in the two species and conforms to the pattern characteristic of divergent character displacement associated with reproductive behaviour. Two alarm calls are quite similar in the two species and are the main vocalizations associated with territorial combat. Their interspecific territorial behaviour has apparently not been affected in areas of sympatry.     

The Breeding Distribution and Habitats of the Pied Flycatcher (Muscicapa Hypoleuca) in Britain

Examination of the plumage of Palaearctic warblers as migrants or wintering birds at Kampala, Uganda, provided useful material for a consideration of moult in relation to the timing of spring and autumn migration. Reasons are suggested for observed interspecific differences in the moult pattern, and for the variation reported from different wintering areas in the African continent.     

Niche partitioning of two Palearctic passerine migrants with Afrotropical residents in their West African winter quarters

In bird migration systems, the question of coexistence and competitionof migrants with residents in the nonbreeding season and theirrole in shaping the evolution of present avian communities ismuch debated. However, conclusions are often drawn in a speculativeway. In the Palearctic-African bird migration system, many studieshave addressed the question of coexistence of Palearctic breedingbirds with Afrotropical species in the former's wintering grounds.These studies have led to some generalizations concerning habitatselection and foraging ecology about the traits that might enablemigrants to coexist with residents. Migrants were thereforeassumed to forage in more open habitats, in more peripheralparts of the vegetation and with a higher foraging speed thanresidents. Furthermore, they were also assumed to be more flexiblein foraging behavior by using a wider range of foraging tactics,but some studies revealed contradicting results. We studiedthe ecology of Palearctic migrants in Comoé NationalPark, Ivory Coast, West Africa, during three successive wintersto explore the factors of niche partitioning between migrantsand residents and to test the hypothesis of whether there arecommon behavioral traits in migrants. Therefore, we comparedthe ecology of two Palearctic breeding species: pied flycatcher,Ficedula hypoleuca, and willow warbler, Phylloscopus trochilus,with resident members of the respective guilds. With respectto use of microhabitat, foraging speed, and intake rates, wecould not confirm the above-mentioned generalizations, showingthat care has to be taken into account when drawing conclusionsfrom few studies for a whole migration system on a huge continent.However, both migrating species were more flexible in foragingbehavior than were their Afrotropical counterparts. As thereare hints that this is also the case when migrants are comparedwith residents on their breeding grounds, we suggest that thisflexibility enables migrants to partition resources with residentsand, therefore, coexist with Afrotropical species. We discuss,however, whether this flexibility is an adaptation to migratorybehavior or a prerequisite for the evolution of migration. Therole that competition plays in present communities cannot besolved with a few observational studies because of the followingproblems. First, it is difficult to detect competition in thefield. Second, there are constraints of performing field experimentsthat have not previously been performed in Africa, and third,there are several possible hypothetical scenarios about therole of competition in shaping present communities, includingfactors that might have been important in the past and are thereforeimpossible to detect at present.     

Distribution and reproductive success of the Pied Flycatcher Ficedula hypoleuca in relation to forest patch size and vegetation characteristics; the effect of scale

We studied habitat choice, distribution and reproductive success in the Pied Flycatcher Ficedula hypoleuca in relation to the spatial structure of a fragmented forest area. Two hierarchical levels of forest habitat structure were used: (1) forest patch size (macrohabitat) and (2) vegetative structure within forest patches (microhabitat). In spring, both males and females settled preferentially in large and medium-sized forest stands (>1 ha) where breeding density was also higher than in small stands (<1 ha). Stands <5 ha were occupied later, and the proportion of unpaired males was higher there than in large stands (>5 ha). The known age distributions of breeding birds and breeding success were independent of forest patch size. Nest predation rate was not associated with stand size or nest distance from the forest edge. The preference of breeding birds for large forest patches was presumably related to the higher amount of resources (nest sites, mates, food) a large patch can offer for reproduction compared with a small patch. At the microhabitat level, territories of old males were characterized by relatively more deciduous trees that contained more invertebrate food than coniferous tree-dominated territories of yearling males. The reproductive success of old males, as measured by the number of fledged young per male, was higher than that of yearling males. This suggests that the larger body size and blacker plumage of old males possibly contributed to male dominance and that old males excluded younger males from preferred habitats through territorial behaviour. Our results suggest that habitat choice of the Pied Flycatcher was affected by both micro- and macrohabitat. On the basis of settlement pattern, density and reproductive success, the distribution of Pied Flycatchers across forest stands of different sizes followed the ideal-free distribution model, whereas at the microhabitat level, age-related unequal distribution of males followed the ideal-despotic model of Fretwell and Lucas.     

Structural and functional aspects of variation of the breeding plumage ornamentation in the male Pied Flycatcher Ficedula hypoleuca (Aves: passeriformes)

Inter- and intraindividual variation of the breeding plumage ornamentation in male Pied Flycatcher Ficedula hypoleuca from the Moscow province population (55 degrees 44' N 36 degrees 51' E) was studied using long-term data (1996-2005). Eumelanin prevailing colour type (CT) scored according to the seven-step Dorst scale (Dorst, 1936), age, and reproductive status during the current breeding season were analyzed as potential sources of variation of the white ornamentation on the forehead, the wings, and the tail in males. Male CT strongly varied, from almost black to cryptic brownish (2-7, average 4.4, N = 1403). On average CT became I1degree darker with age and tended to be stable after the age of two years. Initial and final CT strongly correlated (r = 0.76). Wing ornamentation and forehead patch (FP) were associated with both initial and final CT, whereas correlation between tail ornamentation and CT was observed only in aged males. Ornamentation was most variable in males with cryptic (pale) CT. Such males had, on average, less intense forehead and wing ornamentation than conspicuous males, compensating this difference by having more intense ornamentation next year. These data suggest the weakening of morphogenetic relations between prevailing colour and ornamentation in males with cryptic phenotype. The return rate (rate of conspicuous males returning to their previous nesting territory) was not related to the success of their previous breeding attempts. Among pale males, the return rate was higher in breeders than in non-breeders. The relation between FP shape and reproductive status was pronounced only in pale males. Among pale males, previous breeders and non-breeders displayed no difference in the degree of prevailing colour darkening next year. In conspicuous males, previous breeding led to the weakening of dorsal eumelanin pigmentation of the new plumage, which suggests the existence of tradeoffs between reproductive efforts and the development of rich eumelanin coloration. Among pale males, previous breeders displayed a higher rate of FP widening next year than previous non-breeders. Diffrerent patterns of relations between male ornamentation and reproductive experience suggest that the females can use plural clues to evaluate the quality of their potential mates.     

Neuroanatomical Distribution and Variations across the Reproductive Cycle of Aromatase Activity and Aromatase-Immunoreactive Cells in the Pied Flycatcher (Ficedula hypoleuca)

The anatomical distribution and seasonal variations in aromatase activity and in the number of aromatase-immunoreactive cells were studied in the brain of free-living male pied flycatchers (Ficedula hypoleuca). A high aromatase activity was detected in the telencephalon and diencephalon but low to negligible levels were present in the optic lobes, cerebellum, and brain stem. In the diencephalon, most aromatase-immunoreactive cells were confined to three nuclei implicated in the control of reproductive behaviors: the medial preoptic nucleus, the nucleus of the stria terminalis, and the ventromedial nucleus of the hypothalamus. In the telencephalon, the immunopositive cells were clustered in the medial part of the neostriatum and in the hippocampus as previously described in another songbird species, the zebra finch. No immunoreactive cells could be observed in the song control nuclei. A marked drop in aromatase activity was detected in the anterior and posterior diencephalon in the early summer when the behavior of the birds had switched from defending a territory to helping the female in feeding the nestlings. This enzymatic change is presumably controlled by the drop in plasma testosterone levels observed at that stage of the reproductive cycle. No change in enzyme activity, however, was seen at that time in other brain areas. The number of aromatase-immunoreactive cells also decreased at that time in the caudal part of the medial preoptic nucleus but not in the ventromedial nucleus of the hypothalamus (an increase was even observed), suggesting that differential mechanisms control the enzyme concentration and enzyme activity in the hypothalamus. Taken together, these data suggest that changes in diencephalic aromatase activity contribute to the control of seasonal variations in reproductive behavior of male pied flycatchers but the role of the telencephalic aromatase in the control of behavior remains unclear at present.     

Comparative day and night feeding strategies of shorebird species in a tropical environment

A study was carried out in northeastern Venezuela to determine whether or not shorebirds feed at night in tropical environments. Results show that some Neotropical residents and Nearctic winter migrants feed during darkness. During daylight, Black-winged Stilts Himantopus himantopus, mexicanus group, were predominantly visual foragers (75% attempts were pecking), performing a tactile type of feeding technique (immersion of the whole head and portion of the neck while searching for food through soft mud) on other occasions. During night-time, they were almost equally visual (pecking) and tactile (multiple scythelike sweeps) foragers. Greater and Lesser Yellowlegs Tringa melanoleuca and T. flavipes foraged visually during daylight and tactilely (sidesweeping) at night. Short-billed Dowitchers Limnodromus griseus were tactile feeders (probers) both by day and by night while Semipalmated Plovers Charadrius semipalmatus during daylight and at night and Wilson's Plovers C. tvilsonia by night were sight feeders (peckers). Prey abundance was higher at night than during daylight. Black-winged Stilts and yellowlegs seemed to feed at night on food items at least partly different from those they fed upon during daylight.     

A meta-analytic study of the effects of female age on laying-date and clutch-size in the Great Tit Parus major and the Pied Flycatcher Ficedula hypoleuca

The effects of age (1 year-old vs older females) on laying-date and clutch-size of the Great Tit Parus major (in eight independent study areas) and the Pied Flycatcher Ficedula hypoleuca (five areas) were meta-analysed using both published and unpublished records. To standardize comparisons between areas and species, the standardized difference between the means of the two age groups was used as a measure of the magnitude of the age-effect (effect size).
In Great Tits the laying-date of 'young' females was 0.30 standard deviation units later and clutch-size 0.31 units smaller than that of 'old' females. In the Pied Flycatcher the corresponding figures were 0.45 and 0.81, respectively. All the effect size measures were highly significant but for clutch-size the effect size of the Pied Flycatcher was significantly greater than that of the Great Tit. In the Great Tit the effect size of clutch-size was heterogeneous across the different study areas.
It was estimated that the following numbers of unpublished studies showing null results would have to have accumulated in file-drawers before we could say that the results concerning effect sizes are due to sampling bias: for Great Tits 121 studies of laying-date and 196 studies of clutch-size; and for Pied Flycatchers 45 studies of laying-date and 139 studies of clutch-size.     

Delayed effects in aphid-parasitoid systems: Consequences for evaluating biological control species and their use in augmentation strategies

A particular feature of aphid-parasitoid systems is the existence of a delay between parasitisation (sting) and the death of the host (i.e. mummification). This biological trait is generally not considered important for population stability, except if the delay is very long, and hence it is ignored in most population dynamics studies. However, many crops have relatively short durations, and these time delays may have important consequences and cannot be ignored in a dynamics model. In this study, we are looking for the key-factors that influence an aphidparasitoid system population dynamics during a cropping cycle. Specifically, a simple model based on ordinary and delay differential equations and including biologically meaningful parameters was developed for aphidparasitoid systems and used to examine: (1) effect of biological characteristics of both the aphid and the parasitoid on their dynamics, (2) the effect of parasitoid augmentation on the dynamics of the system (e.g.: date, number and importance of the releases of parasitoids), and (3) to compare observedAphis gossypii — Lysiphlebus testaceipes dynamics in a cucumber crop to the predictions of the model. Good fits between the model and the field data were obtained and suggest that this model may be a powerful tool for selecting species of parasitoid and strategies for their use in biological control augmentation programs for aphid pest management.     

Morphological traits and water use strategies in seedlings of Mediterranean coexisting species

The distribution of plants is associated with their different patterns of response to their environment. Mediterranean plants have evolved a number of morphological and physiological adaptations that determine their ability to survive and grow, being an effective water uptake and use important factors for drought resistance. In this article, we evaluated interspecific differences in morphology, biomass allocation, and architectural traits and their relationship with water use strategies in seedlings of seven co-occurring Mediterranean species (Anthyllis cytisoides L., Genista scorpius L. DC., Myrtus communis L., Pistacia lentiscus L., Rosmarinus officinalis L., Spartium junceum L. and Ulex parviflorus Pourr.). The results showed that morphological root features vary among species and they are significantly correlated with root hydraulic conductance and leaf gas exchange variables. Species with high specific root length (SRL) showed a low hydraulic conductance per root length (K _RRL) but high specific hydraulic conductance (K _As). M. communis and P. lentiscus showed the most contrasting water use patterns with respect to the other species studied. The results are not affected when considering phylogenetic relatedness. Thus, the variability observed in root hydraulic properties and leaf gas exchange suggests important mechanisms for understanding species coexistence in water-limited ecosystems.     

Population genetics and reproductive strategies of two Notostraca (Crustacea) species from winter ponds in Israel

Fluorescent-amplified fragment length polymorphism (FAFLP) fingerprinting assay was used to compare the genetic diversity within and between tadpole shrimps (Notostraca) populations of Lepidurus apus (n=7) and Triops cancriformis (n=2) from rain pools in Israel. Each ephemeral water body has revealed a unique fingerprint pattern with an entailed genetic drift between nearby ponds. High similarity of genotypic diversity within each geographic area led to three clusters of water bodies, north, south and center of Israel. FAFLP assays on several newly hatched individuals of T. cancriformis revealed high identity amongst kin, as compared to L. apus where newly hatched from the same maternal source showed high diversity. Results indicate that T. cancriformis populations from Israel are probably parthenogenetic as indicated by clonal structures. The higher genetic variability in the L. apus populations and in laboratory-hatched specimens indicates the existence of sexual reproduction.     

Canine models of Duchenne muscular dystrophy and their use in therapeutic strategies

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder in which the loss of dystrophin causes progressive degeneration of skeletal and cardiac muscle. Potential therapies that carry substantial risk, such as gene- and cell-based approaches, must first be tested in animal models, notably the mdx mouse and several dystrophin-deficient breeds of dogs, including golden retriever muscular dystrophy (GRMD). Affected dogs have a more severe phenotype, in keeping with that of DMD, so may better predict disease pathogenesis and treatment efficacy. Various phenotypic tests have been developed to characterize disease progression in the GRMD model. These biomarkers range from measures of strength and joint contractures to magnetic resonance imaging. Some of these tests are routinely used in clinical veterinary practice, while others require specialized equipment and expertise. By comparing serial measurements from treated and untreated groups, one can document improvement or delayed progression of disease. Potential treatments for DMD may be broadly categorized as molecular, cellular, or pharmacologic. The GRMD model has increasingly been used to assess efficacy of a range of these therapies. A number of these studies have provided largely general proof-of-concept for the treatment under study. Others have demonstrated efficacy using the biomarkers discussed. Importantly, just as symptoms in DMD vary among patients, GRMD dogs display remarkable phenotypic variation. Though confounding statistical analysis in preclinical trials, this variation offers insight regarding the role that modifier genes play in disease pathogenesis. By correlating functional and mRNA profiling results, gene targets for therapy development can be identified.     

Invading species in the Eel River, California: successes, failures, and relationships with resident species

We examined invasions of non-native fishes into the Eel River, California. At least 16 species of fish have been introduced into the drainage which originally supported 12–14 fish species. Our study was prompted by the unauthorized introduction in 1979 of Sacramento squawfish, Ptychocheilus grandis, a large predatory cyprinid. From 1986 to 1990, we conducted growth and diet studies of squawfish, conducted intensive surveys of the distribution and habitat associations of both native and introduced species, and examined the nature of species-habitat and interspecies relationships. We found no evidence for increased growth or expanded feeding habits, compared to native populations, of Sacramento squawfish as they invaded the Eel River drainage. Ten of the introduced species were well established, with four species limited to a reservoir and six species established in streams. The success or failure of introductions of stream species appeared to be a function of the ability of a species to survive the fluctuating, highly seasonal, flow regime. The present mixture of native and exotic species has not formed stable fish assemblages but it seems likely that four habitat-associated assemblages will develop. The overall effect of the successful species introductions has been to assemble a group of species, with some exceptions, that are native to and occur together in many California streams. The assemblages now forming are similar to those found in other California streams. The assemblage characterized by squawfish and suckers is likely to be resistant to invasion, in the absence of human caused habitat modifications.     

Nematode species abundance patterns and their use in the detection of environmental perturbations

If the concepts of biological indices and biomonitoring at the multi-species level are to prove viable, then meiofauna and marine nematodes in particular should be an ideal group with which to test the hypothesis. Many attempts to assess the structure of species assemblages, such as the use of diversity indices, nematode: copepod ratios and the graphical method of log normal plots, have been shown to be theoretically unsound and/or impractical, especially for routine use by extension workers. A method of assessing shifts in dominance patterns which involves all the proportional species abundances is suggested as a better means of comparing diversity. A modified method of rapidly assessing Simpson's dominance-weighted diversity index is also advocated as being of practical use. In combination, they should enable the diversity aspect of the multi-species approach to biomonitoring to be rigorously and exhaustively evaluated.     

A comparison of the song and territorial behaviour of a long-distance migrant, the Marsh Warbler Acrocephalus palustris, in summer and winter

Colour-ringed populations of Marsh Warblers Acrocephalus palustris on breeding and wintering grounds were compared with respect to song and territorial behaviour. Song and territorial defence had a short duration on the breeding grounds, peaking during the period of mate acquisition and mate-guarding. Some males later showed polyterritorial behaviour. Wintering Marsh Warblers sang and showed defensive behaviour for a longer period which included moult. This behaviour could be described in terms of defence of a short-term resource (a fertile female) in the summer and long-term defence of a reliable food resource in the winter.     

Different feeding strategies in Antarctic scavenging amphipods and their implications for colonisation success in times of retreating glaciers

Background

Scavenger guilds are composed of a variety of species, co-existing in the same habitat and sharing the same niche in the food web. Niche partitioning among them can manifest in different feeding strategies, e.g. during carcass feeding. In the bentho-pelagic realm of the Southern Ocean, scavenging amphipods (Lysianassoidea) are ubiquitous and occupy a central role in decomposition processes. Here we address the question whether scavenging lysianassoid amphipods employ different feeding strategies during carcass feeding, and whether synergistic feeding activities may influence carcass decomposition. To this end, we compared the relatively large species Waldeckia obesa with the small species Cheirimedon femoratus, Hippomedon kergueleni, and Orchomenella rotundifrons during fish carcass feeding (Notothenia spp.). The experimental approach combined ex situ feeding experiments, behavioural observations, and scanning electron microscopic analyses of mandibles. Furthermore, we aimed to detect ecological drivers for distribution patterns of scavenging amphipods in the Antarctic coastal ecosystems of Potter Cove. In Potter Cove, the climate-driven rapid retreat of the Fourcade Glacier is causing various environmental changes including the provision of new marine habitats to colonise. While in the newly ice-free areas fish are rare, macroalgae have already colonised hard substrates. Assuming that a temporal dietary switch may increase the colonisation success of the most abundant lysianassoids C. femoratus and H. kergueleni, we aimed to determine their consumption rates (g food x g amphipods^?1 x day^?1) and preferences of macroalgae and fish.

Results

We detected two functional groups with different feeding strategies among scavenging amphipods during carcass feeding: carcass ‘opener’ and ‘squeezer’. Synergistic effects between these groups were not statistically verified under the conditions tested. C. femoratus switched its diet when fish was not available by consuming macroalgae (about 0.2 day^?1) but preferred fish by feeding up to 80% of its own mass daily. Contrary, H. kergueleni rejected macroalgae entirely and consumed fish with a maximal rate of 0.8 day^?1.

Conclusion

This study reveals functional groups in scavenging shallow-water amphipods and provides new information on coastal intraguild niche partitioning. We conclude that the dietary flexibility of C. femoratus is a potential ecological driver and central to its success in the colonisation of newly available ice-free Antarctic coastal habitats.