Geographic variation in breeding parameters of the Pied Flycatcher Ficedula hypoleuca

Variation in laying date, clutch-size and number of fledglings of the Pied Flycatcher Ficedula hypoleuca was studied in relation to altitude, habitat and latitude, using data from 99 breeding areas from 35̀ N to 70̀ N. Laying date significantly increased with altitude and showed a significant quadratic relationship with latitude, with the earliest values at about 50̀ N. This quadratic relationship shows the same pattern as the relationship between arrival time of adults on the breeding areas and latitude. Clutch-size variation was significantly related to altitude and habitat, small clutches being laid at high altitude and in coniferous forests. Number of fledglings was significantly affected by habitat type, with lower values in the coniferous than in the deciduous forest. Mean clutch-size and mean number of fledglings showed the same quadratic relationship with latitude. In contrast to some earlier studies, an increased clutch-size with latitude was found, mainly because of new data from areas in the southern part of the species' distribution.     

Paternity Loss in Relation to Male Age, Territorial Behaviour and Stress in the Pied Flycatcher

For sexual selection to operate in monogamous species, males of poor quality in some factor like age, ornamentation, condition or aggressiveness, should lose paternity compared with higher quality males. We tested this idea in an Iberian population of pied flycatchers ( Ficedula hypoleuca ). Microsatellite analysis of 67 broods revealed moderate levels of extra-pair paternity (22.4% of broods, 7.5% of young). In a sample of 58 broods for which the caring male was identified, a higher paternity loss was associated with younger males, males that were less aggressive during territorial intrusion tests performed before the commencement of laying, and with males that showed higher levels of corticosterone metabolites in faecal samples collected at the end of the nestling period. Plumage darkness, forehead patch size and condition were not related to paternity loss. Paternity loss is more related to behavioural or physiological traits than to morphological ones in this population.     

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.     

Wulst Neurons in Nestlings of the Pied Flycatcher Ficedula hypoleuca at the Pre-Visual Stage of Development

Neurons of the Wulst region, an analog of the mammalian visual cortex, were studied in Golgi-impregnated preparations of brain of non-precocial 1-day old nestlings of the pied flycatcher Ficedula hypoleuca. At this age, vision does not function in nestlings, their behavior is provided by an acoustic analyzer. Two populations of nerve cells, large and small juvenile neurons, were differentiated at visual examination. The comparative morphometry has shown these groups to differ significantly from each other by most studied parameters: the area of the profile field of their soma, the total length of dendrites, branching of the cell, the number of the maximal branching foci, the character of distribution of dendrite free endings in three concentric zones of the cell dendritic field. The distribution of dendrites in the dendritic neuron field was similar in the both groups of neurons. An increased density of dendrites was observed from the side of the afferent input. At the same time, study of orientation of the longest dendrite has shown it to be located parallel to the plane of the afferent input practically in all cells of the both groups. It is suggested that such orientation of the longest dendrite broadens the area of cell contacts, which is necessary for search for the maximal number of afferents. The predominant orientation of dendrites in the direction to the afferent input forms foundation for establishing a more extended zone of contacts with growing visual afferents.     

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.     

Microhabitat use and feeding strategies of the Pied Flycatcher and the Willow Warbler in their West-African winter quarters compared with resident species

Salewski, V. 2000. Microhabitat use and feeding strategies of the Pied Flycatcher and the Willow Warbler in their West-African winter quarters compared with resident species. Ostrich 71 (1 & 2): 191–193.

Habitat choice, microhabitat and foraging behaviour of the palaearctic Pied Flycatcher and Willow Warbler are described in their West-African wintering areas and are compared with those of resident species. The migrants were more flexible in habitat choice and foraging techniques, but in general did not feed in more open habitat.     

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.     

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.     

The Invasion of Barred Owls and its Potential Effect on the Spotted Owl: a Conservation Conundrum

The spotted owl (Strix occidentalis) is a threatened species in many areas of its western North American range. Concomitant with its decline has been a rapid invasion of its range and habitat by barred owls (Strix varia), a native species that was restricted, until relatively recently, to eastern North America. We assess the theoretical potential for negative interactions between these two owls by examining size dimorphism and ecological relationships within various owl assemblages throughout the world. We then review the anecdotal, natural history, modeling, and experimental evidence that suggest barred owls may negatively affect spotted owls with at least a potential for the competitive exclusion of spotted owls by barred owls throughout all or part of the former’2019;s range. While it is widely accepted that barred owls are either causing or exacerbating declines of spotted owl populations, there are confounding factors, such as habitat loss and bad weather that also may contribute to declines of spotted owls. Both theory and empirical information suggest that barred owls are likely to have negative effects on spotted owl range and density, but the degree of the impact is not predictable. There is a conservation conundrum here, in that the barred owl is a native species that has expanded its range westwards, either naturally or with a degree of human facilitation, and now constitutes a major threat to the viability of another native species, the threatened spotted owl. We propose that only through carefully designed experiments involving removal of barred owls will we be able to determine if recent declines in spotted owl populations are caused by barred owls or by other factors. It is rare in conservation science that replicate study areas exist for which we also have long-standing demographic information, as is the case with the spotted owl. Removal experiments would take advantage of the wealth of data on spotted owls, and allow ecologists to assess formally the impacts of an invasive species on a threatened species, as well as to suggest mitigation measures.     

Effect of Enterostatin on the Feeding Responses to Galanin and NPY

We have investigated the possibility that enterostatin may inhibit the intake of dietary fat by inhibiting either galanin or NPY-induced feeding pathways. Rats, adapted to either high fat (HF) or low fat-high carbohydrate (HC) diets and fitted with third ventricular cannulas were used to study the effects of intracerebroventricular (icv) enterostatin on icv NPY and galanin induced feeding responses in satiated rats. An equimolar dose of enterostatin (0.1nmoles) inhibited, while a tenfold excess of entersotatin abolished the feeding response to galanin in rats adapted to a HF diet. The galanin stimulation of food intake was reduced in rats adapted to the HC diet and this response was less sensitive to inhibition by enterostatin. Enterostatin had no inhibitory effects on NPY-induced feeding in rats adapted to the HC diet and only a small inhibitory effect, at tenfold molar excess, in rats adapted to the HF diet. The ability of enterostatin to bind to galanin or NPY Y-1 receptors was investigated in lig and binding studies. Enterstatin fialed to dispace ¹²⁵I-galanin or ¹²⁵I-PYY from specific binding sites in rat forebrain homogenates or SK-N-MC cells respectively. The data provide support for the hypothesis that enterostatin specifically inhibits a galanin-responsive fat intake system, but indicate that this effect is not modulated by direct interaction with either galanin or NPY-Y1 receptors.