Melanin-based color variation in the Bearded Vulture suggests a thermoregulatory function

We document a case of intraspecific variation in plumage colouration in Bearded Vultures that may have arisen as a functional response to climate conditions. Two subspecies, Gypaetus barbatus barbatus (Eurasia and North Africa populations) and Gypaetus barbatus meridionalis (Eastern and Southern Africa), have been described on the basis of plumage colour differences. The plumage of G. b. barbatus tends to be darker in comparison with that of G. b. meridionalis. The plumage of the two subspecies differ in the feathering of the tarsi (more abundant in G. b. barbatus) and presence/absence of dark ear tufts (only present in G. b. barbatus, and this being the most useful character to distinguish adult specimens of both subspecies). When exposing skins under the sun or to electric bulbs in a cold room, temperature increases were significantly higher in the black ear tufts than in the frontal region of the head, suggesting that the melanized ear patch of G. b. barbatus serves, at least, to heat up the air entering the ear channel and perhaps also the underlying skin. In addition, G. b. barbatus, which inhabits mountainous regions with harsh and long winters, would benefit more from feathered tarsi to prevent heat loss through the legs.     

Colonization history of atlantic island common chaffinches (Fringilla coelebs) revealed by mitochondrial DNA

Common chaffinches (Fringilla coelebs) are thought to have colonized the Atlantic island archipelagoes (the Azores, Madeira, and the Canaries) from neighboring continental populations (Iberia and north Africa) within the last million years. However, colonization may have occurred separately from north Africa to the Canaries and from Iberia to the Azores (as would be predicted geographically) or in one wave from Iberia to the Azores and then to Madeira and the Canaries. These alternatives have different implications for the evolution of morphometric and plumage differentiation in island chaffinches. To determine the most likely colonization route, we estimated the phylogenetic relationships among island and continental subspecies of common chaffinch using sequences from four mtDNA genes (cytochrome b, ATPase 6, NADH 5, and the control region). The most strongly supported mtDNA phylogeny places the continental subspecies together as the sister group to a monophyletic clade containing the island subspecies. This is consistent with a single wave of colonization, and suggests that patterns of similarity among Atlantic island common chaffinches, such as blue pigmentation, short wings, and long tarsi, are due to common colonization history rather than to convergent evolution in a common island environment. However, spectral analysis of phylogenetic splits showed that although monophyly of island haplotypes is favored, there is also substantial support for their polyphyletic origin. We attribute the latter to the confounding effect of homoplasy at multistate sites and to the relatively rapid sequence of colonization events which provided insufficient time for the accumulation of strong phylogenetic signal. These problems are likely to be significant impediments in attempts to test hypotheses of phylogenetic histories of recently evolved populations and taxa.     

Population dynamics of the bearded vulture Gypaetus barbatus in southern Africa

The essential features of mortality and survivorship of bearded vultures Gypaetus barbatus in southern Africa were deduced from age class plumage characteristics. The population consisted of about 204 adult pairs within a breeding range of about 35,000 sq km. Pairs bred every year and produced, on average, about 0·9 young per pair per year. Young birds made up about 37% of the population, subadults 3·5% and adults 60%. About 182 fledged young were recruited to the population each year. The proportion of young birds in the population in different areas was inversely related to the breeding density of adult birds (range 24–47%). Young bird mortality over the four years to subadult age was 87%, the survival rate of adults was 94% and the mean lifespan of birds surviving to adulthood was 21·4 years. This study demonstrates the need to understand the relationship between adult breeding density and young bird numbers in different parts of their range to accurately deduce population dynamics characteristics.     

Testosterone treatment of female Superb Fairy-wrens Malurus cyaneus induces a male-like prenuptial moult, but no coloured plumage

When selection strongly favours a testosterone-dependent trait in males, and this trait is not beneficial to females, a correlated response to selection in females, which also circulate some testosterone, could slow the rate of evolution in males. Here I investigate whether experimental testosterone treatment in female Superb Fairy-wrens Malurus cyaneus can induce the testosterone-dependent sexually selected moult into nuptial plumage, as it does in males. Silastic testosterone implants in females rapidly induced a moult akin to the male prenuptial moult, involving all body areas that are colourful in nuptial males (head, upper back, ear tufts, breast). Moreover, the newly moulted feathers had a similar glistening appearance and morphology as male nuptial feathers. However, the treatment failed to induce production of the blue and black structural colours, and the breast and ear tufts were lighter than the normal grey-brown feathers of females and males in eclipse plumage. Microscopic and ultrastructural analyses of these unusual feathers could further our understanding of structural colour production.     

Organization and variation of the mitochondrial control region in two vulture species, Gypaetus barbatus and Neophron percnopterus

We report the first entire mitochondrial DNA (mtDNA) control region sequences in two endangered vulture species, the bearded vulture (Gypaetus barbatus) and the Egyptian vulture (Neophron percnopterus). Results showed that the general organization of vulture control regions was very similar to other birds, with three distinct domains: a left variable domain (DI), a central conserved one (DII) including the F, E, D, and C boxes, and a right domain (DIII) containing the CSB1 sequence. However, due to the presence of long tandem repeats, vulture control regions differed from other avian control regions both in size and nucleotide composition. The Egyptian vulture control region was found to be the largest sequenced so far (2031 bp), due to the simultaneous presence of repeats in both DI (80 bp) and DIII (77 bp). Low variation was found in vulture control regions, particularly in G. barbatus, as the probable result of populations declines in the last few centuries.     

Population history,gene flow,and bottlenecks in island populations of a secondary seed disperser,the southern grey shrike (Lanius meridionalis koenigi)

Studying the population history and demography of organisms with important ecological roles can aid understanding of evolutionary processes at the community level and inform conservation. We screened genetic variation (mtDNA and microsatellite) across the populations of the southern grey shrike (Lanius meridionalis koenigi) in the Canary Islands, where it is an endemic subspecies and an important secondary seed disperser. We show that the Canarian subspecies is polyphyletic with L. meridionalis elegans from North Africa and that shrikes have colonized the Canary Islands from North Africa multiple times. Substantial differences in genetic diversity exist across islands, which are most likely the product of a combination of historical colonization events and recent bottlenecks. The Eastern Canary Islands had the highest overall levels of genetic diversity and have probably been most recently and/or frequently colonized from Africa. Recent or ongoing bottlenecks were detected in three of the islands and are consistent with anecdotal evidence of population declines due to human disturbance. These findings are troubling given the shrike's key ecological role in the Canary Islands, and further research is needed to understand the community‐level consequences of declines in shrike populations. Finally, we found moderate genetic differentiation among populations, which largely reflected the shrike's bottleneck history; however, a significant pattern of isolation‐by‐distance indicated that some gene flow occurs between islands. This study is a useful first step toward understanding how secondary seed dispersal operates over broad spatial scales.     

Experimental evidence that extra-pair mating drives asymmetrical introgression of a sexual trait

Theory suggests that traits under positive selection may introgress asymmetrically across a hybrid zone, potentially driven by sexual selection. Two subspecies of the red-backed fairy-wren (Malurus melanocephalus) differ primarily in a sexual signal used in mate choice—red versus orange male back plumage colour—but phylogeographic analyses suggest asymmetrical introgression of red plumage into the genetic background of the orange subspecies. We hypothesized that this asymmetrical introgression may be facilitated by sexual selection if red males have a mating advantage over orange males. We tested this hypothesis with correlational data and a plumage manipulation experiment where we reddened the back plumage of a subset of orange males to mimic males of the red subspecies. There was no correlational evidence of a mating advantage to naturally redder males in this population. Experimentally reddened males sired a similar amount of within-pair young and lost paternity at the same rate as orange males, but they sired significantly more extra-pair young, leading to substantially higher total reproductive success. Thus, we conclude that sexual selection via extra-pair mating is a likely mechanism responsible for the asymmetrical introgression of plumage colour in this system, and is potentially driven by a sensory bias for the red plumage signal.     

Differential rates of phenotypic introgression are associated with male behavioral responses to multiple signals

Sexual selection on multiple signals may lead to differential rates of signal introgression across hybrid zones if some signals contribute to reproductive isolation but others facilitate gene flow. Competition among males is one powerful form of sexual selection, but male behavioral responses to multiple traits have not been considered in a system where traits have introgressed differentially. Using playbacks, mounts, and a reciprocal experimental design, we tested the hypothesis that male responses to song and plumage in two subspecies of red‐backed fairy‐wren (Malurus melanocephalus) explain patterns of differential signal introgression (song has not introgressed, whereas plumage color has introgressed asymmetrically). We found that males of both subspecies discriminated symmetrically between subspecies’ songs at a long range, but at a close range, we found that aggression was equal for both subspecies’ plumage and songs. Taken together, our results suggest that male behavioral responses hinder the introgression of song, but allow for the observed asymmetrical introgression of plumage. Our results highlight how behavioral responses are a key component of signal evolution when recently divergent taxa come together, and how differential responses to multiple signals may lead to differential signal introgression and novel trait combinations.     

Unusual feather structure allows partial plumage wettability in diving great cormorants Phalacrocorax carbo

The great cormorant Phalacrocorax carbo is thought to have a wettable plumage, providing low body insulation during foraging. Great cormorants should thus be constrained by water temperatures, and show high energy requirements. Surprisingly, this species has one of the widest breeding distributions of all diving birds, and does not require more food than these other species. We explored this apparent paradox by comparing the insulative properties of body plumage in four subspecies of great cormorants ranging from tropical to polar regions. We found that all subspecies retained an insulating air layer in their plumage, which was, however, much thinner than for other species of diving birds. Detailed examination of the plumage showed that each cormorant body feather has a loose, instantaneously wet, outer section and a highly waterproof central portion. This indicates that the plumage of great cormorants is only partly wettable, and that birds maintain a thin layer of air in their plumage. Our findings suggest an unusual morphological-functional adaptation to diving which balances the antagonist constraints of thermoregulation and buoyancy.     

Male-male mountings in polyandrous bearded vultures Gypaetus barbatus: an unusual behaviour in raptors

Male-male mountings appear to be very common in polyandrous bearded vulture Gypaetus barbatus trios. We observed sexual activity in two trios that occupied the same territory in different years. We recorded a total of 167 copulation attempts. The percentage of male-male mountings recorded was 26.1 and 11.4%, in the period of 1991–1992 and 2000–2001, respectively, with respect to total, homo- and heterosexual matings. We conclude that homosexual interactions do not appear to be directly associated with intrasexual competition (i.e. hierarchical dominance, sperm competition). Rather, our results are more consistent with the idea that this behaviour can regulate the aggression of the males in these groups.     

The evolution of black plumage from blue in Australian fairy‐wrens (Maluridae): genetic and structural evidence

Genetic variation in the melanocortin‐1 receptor (MC1R) locus is responsible for color variation, particularly melanism, in many groups of vertebrates. Fairy‐wrens, Maluridae, are a family of Australian and New Guinean passerines with several instances of dramatic shifts in plumage coloration, both intra‐ and inter‐specifically. A number of these color changes are from bright blue to black plumage. In this study, we examined sequence variation at the MC1R locus in most genera and species of fairy‐wrens. Our primary focus was subspecies of the white‐winged fairy‐wren Malurus leucopterus in which two subspecies, each endemic to islands off the western Australian coast, are black while the mainland subspecies is blue. We found fourteen variable amino acid residues within M. leucopterus, but at only one position were alleles perfectly correlated with plumage color. Comparison with other fairy‐wren species showed that the blue mainland subspecies, not the black island subspecies, had a unique genotype. Examination of MC1R protein sequence variation across our sample of fairy‐wrens revealed no correlation between plumage color and sequence in this group. We thus conclude that amino acid changes in the MC1R locus are not directly responsible for the black plumage of the island subspecies of M. leucopterus. Our examination of the nanostructure of feathers from both black and blue subspecies of M. leucopterus and other black and blue fairy‐wren species clarifies the evolution of black plumage in this family. Our data indicate that the black white‐winged fairy‐wrens evolved from blue ancestors because vestiges of the nanostructure required for the production of blue coloration exist within their black feathers. Based on our phylogeographic analysis of M. leucopterus, in which the two black subspecies do not appear to be each other's closest relatives, we infer that there have been two independent evolutionary transitions from blue to black plumage. A third potential transition from blue to black appears to have occurred in a sister clade.     

Age categories and corresponding gender characteristics of five Crested Francolin subspecies (genus Dendroperdix)

Fifty-five Crested Francolins, Dendroperdix sephaena sephaena, were trapped, marked, retrapped and observed from 1984 to 1988 to assess and describe gender and age criteria based on morphological measurements and plumage characteristics on the farm La Boheme (Rustenburg, North West province, South Africa). The measurements and characteristics were compared with skin specimens of the other recognied subspecies endemic to Africa, namely D. s. zambesiae, D. s. grantii, D. s. spilogaster and D. s. rovuma. Selected biometric parameters of specimens were measured at the Ditsong Museum of Natural History and the American Museum of Natural History in 2014. The purpose of this study was to describe age categories (excluding chicks) with corresponding gender characteristics based on morphology and plumage features. This study revealed six definitive age/gender categories. A combination of spur length (or absence of long spurs in the case of females) and feather colouration patterns on the back, tail coverts, wing coverts and mantle are reliable indicators of different gender/age categories in all D. sephaena subspecies in Africa.     

Geographic variation in the plumage coloration of willow flycatchers Empidonax traillii

The ability to identify distinct taxonomic groups of birds (species, subspecies, geographic races) can advance ecological research efforts by determining connectivity between the non‐breeding and breeding grounds for migrant species, identifying the origin of migrants, and helping to refine boundaries between subspecies or geographic races. Multiple methods are available to identify taxonomic groups (e.g., morphology, genetics), and one that has played an important role for avian taxonomists over the years is plumage coloration. With the advent of electronic devices that can quickly and accurately quantify plumage coloration, the potential of using coloration as an identifier for distinct taxonomic groups, even when differences are subtle, becomes possible. In this study, we evaluated the degree to which plumage coloration differs among the four subspecies of the willow flycatcher Empidonax traillii, evaluated sources of variation, and considered the utility of plumage coloration to assign subspecies membership for individuals of unknown origin. We used a colorimeter to measure plumage coloration of 374 adult willow flycatchers from 29 locations across their breeding range in 2004 and 2005. We found strong statistical differences among the mean plumage coloration values of the four subspecies; however, while individuals tended to group around their respective subspecies’ mean color value, the dispersion of individuals around such means overlapped. Mean color values for each breeding site of the three western subspecies clustered together, but the eastern subspecies’ color values were dispersed among the other subspecies, rather than distinctly clustered. Additionally, sites along boundaries showed evidence of intergradation and intermediate coloration patterns. We evaluated the predictive power of colorimeter measurements on flycatchers by constructing a canonical discriminant model to predict subspecies origin of migrants passing through the southwestern U.S. Considering only western subspecies, we found that individuals can be assigned with reasonable certainty. Applying the model to migrants sampled along the Colorado River in Mexico and the U.S. suggests different migration patterns for the three western subspecies. We believe that the use of plumage coloration, as measured by electronic devices, can provide a powerful tool to look at ecological questions in a wide range of avian species.     

7. SHORT NOTES FROM MEMBERS

Cooper, J., Ross, G. J. B. &; Shaughnessy, P. D. 1978. Seasonal and spatial distribution of Rockhopper Penguins ashore in South Africa. Ostrich 49:40-44. There are 30 records of Rockhopper Penguins Eudyptes chrysocome ashore in South Africa. Both the southern subspecies E.c. chrysocome, and the northern subspecies E.c. moseleyi have been recorded. The northern subspecies has occurred more frequently. Most records are of moulting juveniles in January and February. Records of adult birds are more scattered throughout the year. Rockhopper Penguins in South Africa have been recorded only south of 30S. Birds of the northern subspecies probably originate from South Atlantic islands (Tristan da Cunha group and Gough). Birds of the southern subspecies are probably from the Prince Edward Islands.     

Habitat selection, acoustic adaptation, and the evolution of reproductive isolation

We examined barriers to gene flow in a hybrid zone of two subspecies of the song sparrow (Melospiza melodia). We focused on how mating signals and mate choice changed along an environmental gradient and gathered data on the morphology, genetics, ecology, and behavior across the zone. Melospiza m. heermanni of the Pacific slope of California and M. m. fallax of the Sonoran Desert, each distinct in plumage, meet across a steep environmental gradient in southeastern California. Although both subspecies occur in riparian habitat, their occupied habitat differs structurally, the former subspecies occurring in areas with denser understory and greater vertical heterogeneity. Song elements varied concomitantly, as predicted by the acoustic adaptation hypothesis, with heermanni having lower-pitched, more widely spaced elements. Females of both subspecies responded more strongly to homotypic than heterotypic song, and addition of subspecific plumage cues increased response if song was homotypic but not if heterotypic. Females thus assess multiple male traits, weighing song more heavily. Males of both subspecies showed significantly greater agonistic response to homotypic song. Microsatellite variation is correlated significantly with plumage variation across the zone and suggests limited gene flow between the taxa. The association of song and plumage with the environment and in turn with assortative mating suggests a means by which reproductive isolation may evolve or be maintained in hybrid zones.     

Variation in plumage colour of the Great tit Parus major in relation to habitat, season and food

The plumage colour of nestling and adult Great tits Parus major major L. was studied at Trondheim (63 °N, 10 °E), Norway. Nestlings reared in deciduous woodland were yellower than those reared in coniferous woodland, those reared in 1983 were yellower than those in 1982, and the later in the breeding season they were reared the more yellow they were. Furthermore, adults were yellower than nestlings, and for both groups the males were yellower than the females. Experimental interchange of eggs between nests showed that the variation in plumage colour observed between broods was related primarily to the food and not to genetic differences. Sampling, by the neck-collar method, of the food brought by the parent birds showed that the yellower nestlings received a greater proportion of lepidopteran larvae, in particular greenish-coloured ones, than did the nestlings with a paler plumage. A speculation is whether or not the variation in plumage colour has some adaptive value (viz. background matching).
In avian systematics, plumage coloration has been used to distinguish and describe subspecies. The present study shows that such a classification should only be made with certain reservations, until possible variation in the food quality of the subspecies is known to have no influence on plumage coloration.     

Phylogenetic relationships, biogeography and speciation in the avian genus Saxicola

The avian genus Saxicola is distributed throughout Africa, Asia, Europe and various islands across Oceania. Despite the fact that the group has great potential as a model to test evolutionary hypotheses due to the extensive variability in life history patterns recorded between and within species, the phylogenetic relationships among species and subspecies of this genus are poorly understood. We undertook a systematic investigation of the relationships within this genus with three main objectives in mind, (1) to test the monophyly of the genus; (2) to ascertain geographical origin and dispersal sequence; and (3) to test for monophyly within the most morphologically diverse species, S. torquata and S. caprata. We studied sequence data from the mitochondrial cytochrome b gene from 11 of the 12 recognized species and 15 of the 45 described subspecies. Four clades, two exclusively Asian, one Eurasian, and the fourth encompassing Eurasia and Africa, were identified. Based on our analyses, monophyly of the genus Saxicola is not supported and an Asian origin for the genus can be inferred. Results from DIVA analyses, tree topology and nodal age estimates suggest independent colonisation events from Asia to Africa and from Asia to the Western Palearctic, with the Sahara desert acting as a natural barrier for S. torquata. Subspecies and populations of S. torquata are not monophyletic due to S. tectes, S. dacotiae and S. leucura grouping within this complex. Subspecies and populations of S. caprata are monophyletic. Importantly, within S. torquata and S. caprata, slight morphological traits and plumage colour pattern differences used to recognize subspecies are indicative of the greater cryptic diversification that has occurred within this genus.     

Dynamics in the evolution of sexual traits: losses and gains,radiation and convergence in yellow wagtails (Motacilla flava)

We analyse patterns of genetic diversity and song complexity in the Palaearctic yellow wagtail (Motacilla flava), a highly polytypic species complex. Mitochondrial and nuclear DNA show that the complex is polyphyletic, despite parallel plumage variation in western and eastern clades. In the western clade there is genetic structure among southern subspecies, haplotype diversity decreases with latitude, and northern subspecies show evidence of bottlenecking and rapid expansions, as expected from isolation in glacial refugia followed by postglacial colonization. However, northern subspecies, which have more divergent male plumages, lack genetic structure and sing simpler songs. Loss of song complexity and evolution of plumage in founder populations are consistent with the Kaneshiro model, which posits that variation among species is a consequence of founder-induced shifts in female preference leading to loss of ancestral male sexual traits. Our results suggest possible postglacial founder-effect mechanisms for the morhological diversification of the yellow wagtail complex.     

A genetic defect in hyomandibular furrow closure in the Japanese quail: the causes for ear-opening abnormality and formation of an ear tuft

The mutant ET (ear tuft) quail strain is characterized by an ear-opening abnormality frequently accompanied by ear tufts. The mutant ear opening is oval shaped with a fissure on its ventral margin, whereas the ear tufts project from the ventral end of the fissure or the posterior margin of the ear opening. The ear tufts are composed of a feathered peduncle. The size of the ear tufts and the ear-opening abnormality are variable. The incidence of the ear tufts and the ear-opening abnormality in the ET embryos at 15 days of incubation was 33% and 42%, respectively. Examination of early embryos revealed an incomplete closure of the hyomandibular furrow, the incidence of which was 91% in 5 day embryos. It appears that the hyomandibular furrow abnormality is the primary defect leading to the ear-opening and ear-tuft traits. Genetic analyses of hyomandibular furrow closure defect indicated it to be due to an autosomal recessive mutation. The proposed gene symbol is hfd.