Male Feathers Research Articles

Birds of Prey as Indicators of the State of the Environment in Urban Areas

Introduction. The white-tailed eagle is a rare, large species of bird of prey. To restore the species, reserve populations are created in zoological institutions. Birds have a fairly high level of metabolism and are sensitive to pollutants, so it is necessary to monitor the environment and evaluate the quantitative intake of chemicals into the animal organism. Purpose. The aim of the study was to study the effect of environmental pollution on the accumulation of heavy metals (zinc, copper, iron, lead, cadmium and arsenic) by white-tailed eagles living in zoological institutions in the cities of Moscow, Ivanovo and Yaroslavl. Materials and Methods. The assessment of the level of metal concentration was carried out using the developed centile scales, which are planned to assess the development factors of paraneoplastic ophthalmopathies. Results. When studying the differences in the accumulation of heavy metals in the feathers of white-tailed eagles, a significant increase in the concentration of cadmium in the rod by 3.64 times was found, which indicates its external intake. In the feathers of males, compared with females, a significant (p < 0.05) increase in the content of Cu by 13.98 times, Zn - by 8.41 times was revealed. In females, a significant increase in the concentration of Cd by 1.60 times, As - by 12.18 times was found. Conclusions. A reliable average direct relationship between the level of Zn and Fe, Cu and Pb, Cd and As was revealed, which indicates the mutual symbation between these metals in the animal body. Between Zn and As defined antagonistic joint accumulation. The average concentrations of Zn, Cu, Pb and Cd were found in 50% of the specimens of sea eagles, Fe and As in 62.5% of the total number of birds studied. In the studied sample of animals, a tendency to an increase in the accumulation of Fe and As was revealed.

Mercury contamination level is repeatable and predicted by wintering area in a long-distance migratory seabird

The environmental presence of mercury has dramatically increased over the past century, leading to increased uptake, especially by top predators such as seabirds. Understanding the exact sources of contamination requires an individual-level approach, which is especially challenging for species that migrate. We took such an approach and located the wintering areas of 80 common terns (Sterna hirundo) through tracking, and, across years, collected feathers grown in those areas to assess their mercury levels using atomic absorption spectrometry. Although feathers of males and females did not differ in their mercury level, we found the average feather mercury level to be highest in birds wintering in the Canary Current (3.87 μg g−1), medium in birds wintering in the Guinea Current (2.27 μg g−1) and lowest in birds wintering in the Benguela Current (1.96 μg g−1). Furthermore, we found considerable inter-annual fluctuations in feather mercury levels, a within-individual repeatability of 41%, that the mercury levels of 17% of feather samples exceeded the admitted toxicity threshold of 5 μg g−1, and that the overall mean concentration of 3.4 μg g−1 exceeded that of other published reports for the species. Further studies therefore should assess whether these levels lead to individual-level carry-over effects on survival and reproductive performance.

Heavy metals and metalloid levels in the tissues of yellow-legged gulls (Larus michahellis) from Spain: sex, age, and geographical location differences

In the present study, mercury (Hg), cadmium (Cd), lead (Pb), selenium (Se), and arsenic (As) were measured in liver, kidney, and feathers of adult, juvenile, and chick seagulls (Larus michahellis) collected from the northwest of Spain. Age, sex, and the geographical location of samples were considered variables that can influence metal bioaccumulation, for which concentrations were determined by means of ICP-MS. The mean concentrations (dry weight) found in seagulls were 7.01 ± 0.37 mg Hg/kg, 22.82 ± 2.83 mg Cd/kg, 7.36 ± 1.36 mg Pb/kg, 18.64 ± 0.63 mg Se/kg, and 10.64 ± 0.59 mg As/kg. Regarding the different factors analyzed, Hg was the only metal showing sex-related differences, being significantly higher (p < 0.05) the concentrations found in feathers of males (1.26 ± 0.12 mg/kg) than those in females (0.99 ± 0.11 mg/kg). A highly significant (p < 0.01) increase in levels of some metals was found in liver related to the increase of age: Hg (adults (A) 3.33 ± 0.22 mg/kg vs chicks (C) 1.76 ± 0.28 mg/kg), Cd (A 4.74 ± 0.62 mg/kg vs C 1.79 ± 0.2), Pb (A 0.65 ± 0.12 mg/kg vs juveniles 0.4 ± 0.11 mg/kg), and Se (A 7.56 ± 0.43 mg/kg vs C 5.24 ± 0.53 mg/kg). Positive correlations between Cd-Hg and Se–Hg were found in liver (p < 0.001), kidney (p < 0.001), and feathers (p < 0.05 and p < 0.001, respectively). The associations found may reflect antagonistic interactions between Se and Cd on Hg toxicity. The results suggest that L. michahellis can reveal local contamination around the foraging and breeding sites and can be a very useful monitoring instrument for assessing heavy metal contamination and sentinel species of environmental health.

Ornamental Throat Feathers Predict Telomere Dynamic and Hatching Success in Spotless Starling (Sturnus unicolor) Males

Sexually selected signals reliably reflect individual phenotypic or genetic quality and, thus, survival prospects of holders. Telomere length is considered a good predictor of life expectancy and, consequently, exploring the links between telomere length and sexually selected traits is much needed to better understand the mechanisms that maintain the honesty of sexual signals. We manipulated the length of throat feathers in spotless starling (Sturnus unicolor) males (a sexually selected signal) before reproduction and explored its effects on telomere shortening and breeding performance in subsequent reproductive events. We did not detect an effect of the feathers clipping manipulation, but males with longer throat feathers before the experiment had shorter telomeres that also shortened more slowly than those of males with shorter throat feathers did. Moreover, length of throat feathers of males before manipulation was positively related to hatching success of second clutches. Thus, correlative but not experimental results support the expected associations between sexually selected signals, telomeres and reproduction. We discuss such results in scenarios of sexual selection where feather length reflects, but does not directly cause, telomere attrition and enhanced reproductive success. Males with longer throat feathers might be older, more experienced males (i.e., with shorter telomeres), able to buffer telomere shortening between reproductive events. Because of the absence of experimental effects, differential incubation effort of females cannot explain the detected association with hatching success, but other sexually selected traits that covary with throat-feather length could be responsible. Exploring those physiological and/or morphological characteristics related to throat-feather length should therefore be the matter of future research.

Plumage iridescence is associated with distinct feather microbiota in a tropical passerine

Birds present a stunning diversity of plumage colors that have long fascinated evolutionary ecologists. Although plumage coloration is often linked to sexual selection, it may impact a number of physiological processes, including microbial resistance. At present, the degree to which differences between pigment-based vs. structural plumage coloration may affect the feather microbiota remains unanswered. Using quantitative PCR and DGGE profiling, we investigated feather microbial load, diversity and community structure among two allopatric subspecies of White-shouldered Fairywren, Malurus alboscapulatus that vary in expression of melanin-based vs. structural plumage coloration. We found that microbial load tended to be lower and feather microbial diversity was significantly higher in the plumage of black iridescent males, compared to black matte females and brown individuals. Moreover, black iridescent males had distinct feather microbial communities compared to black matte females and brown individuals. We suggest that distinctive nanostructure properties of iridescent male feathers or different investment in preening influence feather microbiota community composition and load. This study is the first to point to structural plumage coloration as a factor that may significantly regulate feather microbiota. Future work might explore fitness consequences and the role of microorganisms in the evolution of avian sexual dichromatism, with particular reference to iridescence.

Pelagic seabirds as biomonitors of persistent organic pollutants in the Southwestern Atlantic.

Persistent Organic Pollutants (POPs) are accumulated through time and can exert different effect on ecosystems. POPs and Chlorpyrifos, a current use pesticide, were assessed in body feathers of males and females of Black-browed albatross (Thalassarche melanophris, BBA) and Cape petrels (Daption capense, CAP) during their non-breeding seasons at the Patagonian Shelf, Argentina. Chlorpyrifos showed the highest values among all pollutants in both species (49.56-84.88 ng g-1), resulting from current agricultural practices. The pattern OCPs > PCBs > PBDEs was observed in both species, and CAP showed higher concentrations than BBA probably as a consequence of higher lipid mobilization and pollutants availability during dispersion. Non-significant differences between sexes about POPs levels were found; however a slight tendency was observed, females>males in CAP, and males>females in BBA. More attention and further studies are needed to understand seabirds' physiology and its relationship with the pollutants distribution in their tissues and considering breeding season.

Defenses against keratinolytic bacteria in birds living in radioactively contaminated areas.

Microorganisms have shaped the evolution of a variety of defense mechanisms against pathogenic infections. Radioactivity modifies bacterial communities and, therefore, bird hosts breeding in contaminated areas are expected to adapt to the new bacterial environment. We tested this hypothesis in populations of barn swallows (Hirundo rustica) from a gradient of background radiation levels at Chernobyl and uncontaminated controls from Denmark. Investment in defenses against keratinolytic bacteria was measured from feather structure (i.e., susceptibility to degradation) and uropygial secretions. We studied degradability of tail feathers from areas varying in contamination in laboratory experiments using incubation of feathers with a feather-degrading bacterium, Bacillus licheniformis, followed by measurement of the amount of keratin digested. The size of uropygial glands and secretion amounts were quantified, followed by antimicrobial tests against B. licheniformis and quantification of wear of feathers. Feathers of males, but not of females, from highly contaminated areas degraded at a lower rate than those from medium and low contamination areas. However, feathers of both sexes from the Danish populations showed little evidence of degradation. Individual barn swallows from the more contaminated areas of Ukraine produced the largest uropygial secretions with higher antimicrobial activity, although wear of feathers did not differ among males from different populations. In Denmark, swallows produced smaller quantities of uropygial secretion with lower antimicrobial activity, which was similar to swallow populations from uncontaminated areas in Ukraine. Therefore, barn swallows breeding in contaminated areas invested more in all defenses against keratinolytic bacteria than in uncontaminated areas of Ukraine and Denmark, although they had similar levels of feather wear. Strong natural selection exerted by radioactivity may have selected for individuals with higher defense capacity against bacterial infections during the 30years since the Chernobyl disaster.

Bacteria and the evolution of honest signals. The case of ornamental throat feathers in spotless starlings

Summary Mechanisms guaranteeing reliability of messages are essential in understanding the underlying information and evolution of signals. Micro‐organisms may degrade signalling traits and therefore influence the transmitted information and evolution of these characters. The role of micro‐organisms in animal signalling has, however, rarely been investigated. Here, we explore a possible role for feather‐degrading bacteria driving the design of ornamental throat feathers in male spotless starlings (Sturnus unicolor). We estimated length, bacterial load, degradation status and susceptibility to degradation by keratinolytic bacteria in those feathers, compared with non‐ornamental adjacent feathers in males, as well as to throat feathers in females. In addition, the volume of the uropygial gland and its secretion was measured and the secretion extracted. We also experimentally evaluated the capacity of each secretion to inhibit growth of a keratinolytic bacterium. The apical part of male ornamental throat feathers harboured more bacteria and degraded more quickly than the basal part; these patterns were not detected in female throat feathers or in non‐ornamental male feathers. Moreover, degradation status of male and female throat feathers did not differ, but was positively associated with feather bacterial density. Finally, the size of the uropygial gland in both males and females predicted volume and the inhibitory capacity of secretion against feather‐degrading bacteria. Only in males was uropygial gland size negatively associated with the level of feather degradation. All results indicate differential susceptibility of different parts of throat feathers to keratinolytic bacterial attack, which supports the possibility that throat feathers in starlings reflect individual ability to combat feather‐degrading bacteria honestly. This is further supported by the relationship detected between antimicrobial properties of uropygial secretion and the level of feather degradation. Our results suggest that selection pressures exerted by feather‐degrading bacteria on hosts may promote evolution of particular morphologies of secondary sexual traits with different susceptibility to bacterial degradation that reliably inform of their bacterial load. Those results will help to understand the evolution of ornamental signals.

Winter body condition in the Collared Flycatcher: Determinants and carryover effects on future breeding parameters

ABSTRACT Factors that determine the condition of migratory birds at their wintering sites are poorly known. Age, sex, and morphological characteristics of birds may have an influence on their winter condition by affecting their foraging and competitive abilities. Winter body condition could have long-term consequences on the reproductive success of migratory birds during the subsequent breeding season. Using 3 yr of data from Collared Flycatchers (Ficedula albicollis), we examined the characteristics of winter-grown tail feathers, as indicators of winter body condition, in relation to sex, age, morphological traits, and future breeding variables. Tail feather mass was highly repeatable between years, but feather growth rate was not repeatable, which suggests that the latter trait mainly indicates environmental circumstances during molt, whereas feather mass may more strongly reflect genetic effects. Tail feathers of males and adults showed better quality than those of females and juveniles, possibly becau...

The proteomics of feather development in pied flycatchers (Ficedula hypoleuca) with different plumage coloration

The genetic theory of morphological evolution postulates that form evolves largely by changing the expression proteins that are functionally conserved. It follows that understanding the function of proteins during different phases of development as well as the mechanisms by which the functions are modified is a prerequisite for understanding evolutionary change. Male pied flycatchers exhibit marked phenotypic variation in their breeding plumage. This variation has repeatedly been shown to have adaptive significance, but the molecular basis of this variation is not known. Here, we characterize the proteome of developing pied flycatcher feathers from differently pigmented males and also introduce a new method for examining the effect sizes of expression differences in protein interaction networks. Approximately 300 proteins were identified in the developing feathers of males. Gene products associated with cellular transport, cell metabolism and protein synthesis formed a large part of the developing feather proteome. Sixty-five proteins associated with the development of the epidermis and/or pigmentation were detected in the data. The examination of expression level differences of protein-protein interaction networks revealed an immunological signalling-related network to exhibit significantly higher expression in black compared to brown males. Additionally, indications of differences in energy balance and oxidative stress related characteristics were detected. Together, these results provide new insight into the molecular mechanisms and evolutionary significance of plumage colour variation.

Factors Influencing the Turnover and Net Isotopic Discrimination of Hydrogen Isotopes in Proteinaceous Tissue: Experimental Results Using Japanese Quail

Stable hydrogen isotopes (δ(2)H) are commonly used in studies of animal movement. Tissue that is metabolically inactive after growth (e.g., feathers) provides spatial or dietary information that reflects only the period of tissue growth, whereas tissues that are metabolically active (e.g., red blood cells) provide a moving window of forensic information. However, using δ(2)H for studies of animal movement relies on the assumption that tissue δ(2)H values reflect dietary δ(2)H values, plus or minus a net diet-tissue discrimination value, and that the turnover rate is known for metabolically active tissue. The metabolic rate of an animal may influence both diet-tissue discrimination values and isotopic tissue turnover rate, but this hypothesis has not been tested experimentally. To examine the metabolic hypothesis, an experimental group of 12 male and 15 female captive Japanese quail (Coturnix japonica) was housed at 8.9°C for 90 d to elevate their metabolic rates (mL CO(2) min(-1)), and a control group of 12 male and 13 female quail was housed at room temperature during the same period. For both experimental and control birds, diet-tissue discrimination values were estimated for red blood cells and feathers. To determine turnover rate, experimental and control birds were switched from a (2)H-enriched diet to a (2)H-depleted diet, with red blood cells sampled before and after diet switch. Metabolic rate did not influence red blood cell hydrogen isotope turnover rate (η(2)(p) = 0.24)) or diet-feather isotope discrimination values (η(2)(p) = 0.86). Diet-feather hydrogen isotopic discrimination had a significant sex plus treatment interaction effect; female feathers were depleted in (2)H relative to food regardless of treatment, whereas male feathers were enriched in (2)H. The effect of sex suggested that experimental studies should examine whether coeval males and females differ in blood δ(2)H levels during certain periods of the annual cycle.

Carotenoid-based plumage coloration in golden-crowned kinglets Regulus satrapa: pigment characterization and relationships with migratory timing and condition

Carotenoid-based ornamental coloration has long been proposed to honestly signal quality due to its dependence on individual condition. Because migration can be one of the most stressful periods of an animal's annual cycle, developing colourful plumage may be particularly challenging for species in which migration and moult periods overlap or occur sequentially. The purpose of this study was to investigate pigmentary and condition-dependent bases of carotenoid colour variation in a small migratory passerine, the golden-crowned kinglet Regulus satrapa (Family Regulidae). We captured 186 male and female kinglets of various ages during fall migration in southwestern Ontario, Canada and recorded arrival date, body condition index, fat and pectoral muscle scores, wing mite infestation, and feather growth rate as measures of condition. We quantified crown coloration using reflectance spectrometry and analyzed feather carotenoids using high-performance liquid chromatography. Yellow crown feathers of female kinglets contained only yellow hydroxycarotenoids, whereas orange feathers of males harboured a suite of eight carotenoid pigments. Males with longer wavelength orange crown hues deposited greater concentrations of ketocarotenoids, especially canthaxanthin. Female kinglets with longer wavelength crown hues and males with longer wavelength crown hues and more saturated crown coloration left for migration earlier in the year. Females with longer wavelength crown hues had fewer feather mites and tended to be in better condition. However, male kinglets with more saturated coloration possessed smaller pectoral muscles. This is the first study to identify plumage carotenoids in this North American bird family and to determine the pigmentary basis for both inter- and intrasexual colour variation. Our results provide further support for the condition-dependence of carotenoid coloration and suggest that ornamental elaboration in both sexes may encode information about fall condition and migratory performance.

Mercury and other metals in eggs and feathers of glaucous-winged gulls (Larus glaucescens) in the Aleutians

Levels of mercury and other contaminants should be lower in birds nesting on isolated oceanic islands and at high latitudes without any local or regional sources of contamination, compared to more urban and industrialized temperate regions. We examined concentrations of arsenic, cadmium, chromium, lead, manganese, mercury and selenium in the eggs, and the feathers of fledgling and adult glaucous-winged gulls (Larus glaucescens) nesting in breeding colonies on Adak, Amchitka, and Kiska Islands in the Aleutian Chain of Alaska in the Bering Sea/North Pacific. We tested the following null hypotheses: 1) There were no differences in metal levels among eggs and feathers of adult and fledgling glaucous-winged gulls, 2) There were no differences in metal levels among gulls nesting near the three underground nuclear test sites (Long Shot 1965, Milrow 1969, Cannikin 1971) on Amchitka, 3) There were no differences in metal levels among the three islands, and 4) There were no gender-related differences in metal levels. All four null hypotheses were rejected at the 0.05 level, although there were few differences among the three test sites on Amchitka. Eggs had the lowest levels of cadmium, lead, and mercury, and the feathers of adults had the lowest levels of selenium. Comparing only adults and fledglings, adults had higher levels of cadmium, chromium, lead and mercury, and fledglings had higher levels of arsenic, manganese and selenium. There were few consistent interisland differences, although levels were generally lower for eggs and feathers from gulls on Amchitka compared to the other islands. Arsenic was higher in both adult feathers and eggs from Amchitka compared to Adak, and chromium and lead were higher in adult feathers and eggs from Adak compared to Amchitka. Mercury and arsenic, and chromium and manganese levels were significantly correlated in the feathers of both adult and fledgling gulls. The feathers of males had significantly higher levels of chromium and manganese than did females. The levels of most metals in feathers are below those known to be associated with adverse effects in the gulls or their predators. However, levels of mercury in some gull eggs are within a range suggesting that several eggs should not be eaten in one day by sensitive humans.

Primary sex ratio adjustment to experimentally reduced male UV attractiveness in blue tits

The study of primary sex ratio adjustment in birds is notorious for inconsistency of results among studies. To develop our understanding of avian sex ratio variation, experiments that test a priori predictions and the replication of previous studies are essential. We tested if female blue tits Parus caeruleus adjust the sex ratio of their offspring to the sexual attractiveness of their mates, as was suggested by a previous benchmark study on the same species. In 2 years, we reduced the ultraviolet (UV) reflectance of the crown feathers of males in the period before egg laying to decrease their attractiveness. In contrast to the simple prediction from sex allocation theory, we found that the overall proportion of male offspring did not differ between broods of UV-reduced and control-treated males. However, in 1 year, the UV treatment influenced offspring sex ratio depending on the natural crown UV reflectance of males before the treatment. The last result confirms the pattern found in the previous blue tit study, which suggests that these complex patterns of primary sex ratio variation are repeatable in this bird species, warranting further research into the adaptive value of blue tit sex ratio adjustment to male UV coloration. Key words: blue tit Parus caeruleus, male attractiveness, primary sex ratio, sex allocation, ultraviolet plumage. [Behav Ecol]

Frequency and consequences of feather holes in Barn SwallowsHirundo rustica

The relationship between feather quality, estimated through the prevalence and intensity of feather holes, and the breeding performance and survival of the Barn SwallowHirundo rusticawas studied over a 5‐year period. In addition, we present some indirect data on the role of chewing lice in producing the feather holes. The balanced distribution of feather holes (high prevalence, low aggregation) corresponds with the pattern of distribution of lice on colonial birds, and in the Barn Swallow. Feather holes were significantly and positively associated with the arrival dates of the birds, as both males and females with an increased number of feather holes started laying later. Females that survived the winter had significantly fewer holes than non‐surviving females, whereas there was no difference in feather hole number between surviving and non‐surviving males. Given that there was no association between the number of feather holes and body condition indices, except for the tail length of male Barn Swallows, we suggest that the negative effect of feather holes on the fitness of the birds is mainly apparent during periods of intensive locomotor activity, such as migration. Alternatively, if feather holes are an indicator of quality, those birds with a high intensity of feather holes may have been of poor quality. These birds may have been less able to cope with the environmental conditions, resulting in the lower survival and later arrival of the birds to the breeding grounds. The negative relationship between the length of the outermost tail feathers of males and the incidence of feather holes suggests that the tail is a condition‐dependent secondary sexual characteristic.

Protandry, sexual selection and climate change

AbstractProtandry refers to the earlier appearance of males before females at sites of reproduction. Sexual selection has been hypothesized to give rise to sex differences in benefits and costs of early arrival, thereby selecting for earlier appearance by the sex subject to more intense sexual selection. If sexual selection is more intense, there is a greater premium on early arrival among individuals of the chosen sex because of direct selection for earlier arrival. This hypothesis leads to the prediction that changes in the costs and benefits of early arrival related to changes in environmental conditions should particularly affect the sex that arrives first and hence the degree of protandry. I tested this hypothesis using the Barn SwallowHirundo rustica. During 1971–2003, the degree of protandry increased significantly in a Danish population because males advanced arrival date while females did not. This earlier arrival by males compared with females was correlated with a significant increase by over 1.2 standard deviations in the length of the outermost tail feathers of males, a secondary sexual character, suggesting direct selection on both protandry and the secondary sexual character. Environmental conditions during spring migration in Northern Africa, as reflected by the normalized difference vegetation index, have deteriorated since 1984, resulting in increased mortality among males during spring migration, but not among females, and this deterioration of climatic conditions was positively correlated with an increasing degree of protandry. Likewise, an increase in April temperatures at the breeding grounds during recent decades is positively correlated with increased protandry, apparently because males can arrive earlier without increasing the fitness cost of early arrival. Local population size did not predict changes in arrival date. These findings suggest that rapid changes in climate can cause a change in degree of protandry and secondary sexual characters.

Rapid evolutionary change in a secondary sexual character linked to climatic change

The ability of organisms to respond evolutionarily to rapid climatic change is poorly known. Secondary sexual characters show the potential for rapid evolutionary change, as evidenced by strong divergence among species and high evolvability. Here we show that the length of the outermost tail feathers of males of the socially monogamous barn swallow Hirundo rustica, feathers that provide a mating advantage to males, has increased by more than 1 standard deviation during the period from 1984 to 2003. Barn swallows from the Danish population studied here migrate through the Iberian Peninsula to South Africa in fall, and return along the same route in spring. Environmental conditions on the spring staging grounds in Algeria, as indexed by the Normalized Difference Vegetation Index, predicted tail length and change in tail length across generations. However, conditions in the winter quarters and at the breeding grounds did not predict change in tail length. Environmental conditions in Algeria in spring showed a temporal deterioration during the study period, associated with a reduction in annual survival rate of male barn swallows. Phenotypic plasticity in tail length of males, estimated as the increase in tail length from the age of 1 to 2 years, decreased during the course of the study. Estimates of directional selection differentials for male tail length with respect to mating success, breeding date, fecundity, survival and total selection showed temporal variation, with the intensity of breeding date selection, survival selection and total selection declining during the study. Response to selection as estimated from the product of heritability and total selection was very similar to the observed temporal change in tail length. These findings provide evidence of rapid micro-evolutionary change in a secondary sexual character during a very short time period, which is associated with a rapid change in environmental conditions.

Female ornamentation and male mate choice in dark-eyed juncos

Traits that enhance attractiveness in one sex may or may not influence attractiveness in the other. In the dark-eyed junco, Junco hyemalis, outer tail feathers of males and females are all or partly white and form a sharp contrast with the bird's mostly grey plumage. The amount of white in these feathers (‘tail white’) is greater in males than in females and, as we report here, is greater in birds that have completed a second prebasic moult than in yearlings. During courtship, male juncos spread their tails, revealing their tail white, and a previous experiment has shown that males with experimentally enhanced tail white are more attractive to females. To determine whether females with experimentally enhanced tail white would be preferred by males, we clipped and replaced tail feathers of females, creating a control group with low to natural levels of tail white and an enhanced group with high levels. We tested preference in a mate choice apparatus like that used previously and found that males courted both control and enhanced females and displayed individual preferences but showed no collective preference for members of either category of females. Because we found neither a preference for trait values that indicate greater age/experience (experimentally enhanced females) nor a preference for less male-like appearance (control females), our results are inconsistent with a role for male mate choice in the maintenance of tail white in females. Female tail white may be subject to selection in another context or persist owing to a genetic correlation between the sexes. Regardless, the sexes apparently prefer different trait values, which suggests that preferences are expressed independently in males and females.

Developmental stability across the breeding distribution of the scissor‐tailed flycatcher (Tyrannus forficatus)

A central question in ecology is how individual fitness interacts with the spatial variation in population density and habitat characteristics across species’ ranges. We used fluctuating asymmetry (FA) as a measure of developmental stability (DS) in individuals of Tyrannus forficatus to estimate the suitability of sites of varying abundance and position within the species’ range. FA in the inner‐tail feathers of males and females is not spatially correlated across the species’ range. FA in males increases towards the centre of the range and is not correlated with abundance. FA in females is not correlated with position in the range or abundance. Our results suggest that optimal sites are found throughout the range of the species, whereas suboptimal sites are mainly found towards the centre of the range. Additionally, our results suggest that abundance may not reflect the suitability of sites across species’ ranges.

Aspects of the moult, morphology and anatomy of rock pigeons

Aspects of the morphology and anatomy of rock pigeons (Columba guinea) were investigated. Moulting apparently takes place throughout the year at a relatively low intensity. Marked peaks in moulting could only be distinguished for the primaries, secondaries and tail feathers of males. The renewal process for females takes place more irregularly. Apart from the bill dimensions, all standard body measurements of adult males are significantly larger than those of females. The opposite tendency occurs in immatures. Seasonal variation in liver and body mass as well as visible fat content of adult individuals can probably be related to breeding activities and the availability of seasonally abundant food sources. In comparison to the other populations sampled, considerable differences in body mass and fat content were noted for the pigeons from South West Africa.