Ornamental Feathers Research Articles

A natural experiment on the condition-dependence of achromatic plumage reflectance in black-capped chickadees.

Honest advertisement models posit that only individuals in good health can produce and/or maintain ornamental traits. Even though disease has profound effects on condition, few studies have experimentally tested its effects on trait expression and even fewer have identified a mechanistic basis for these effects. Recent evidence suggests that black and white, but not grey, plumage colors of black-capped chickadees (Poecile atricapillus) are sexually selected. We therefore hypothesized that birds afflicted with avian keratin disorder, a condition that affects the beak and other keratinized tissues, would show reduced expression of black and white, but not grey, color. UV-vis spectrometry of black-capped chickadees affected and unaffected by avian keratin disorder revealed spectral differences between them consistent with this hypothesis. To elucidate the mechanistic bases of these differences, we used scanning electron microscopy (SEM), electron-dispersive x-ray spectroscopy (EDX) and a feather cleaning experiment. SEM showed extreme feather soiling in affected birds, and EDX revealed that this was most likely from external sources. Experimentally cleaning the feathers increased color expression of ornamental feathers of affected, but not unaffected, birds. These data provide strong evidence that black and white color is an honest indicator in chickadees, and that variation in feather dirtiness, likely due to differences in preening behavior is a mechanism for this association.

Egg yolk antioxidant deposition as a function of parental ornamentation, age, and environment in great tits Parus major

Females can modify phenotype of their offspring through the deposition of biologically active compounds into eggs, including carotenoids, vitamins and other antioxidants. Understanding patterns of deposition is critical for better insight into the significance of maternal effects. Here we investigated how egg yolk antioxidants (lutein, zeaxanthin, β-carotene, vitamin A and E) related to environmental conditions and parental characteristics in great tits Parus major using data from three breeding seasons. Male and female traits included condition, age and multiple feather ornaments, both carotenoid- and melanin-based (carotenoid and UV chroma of yellow breast feathers, area of black breast band, white cheek immaculateness). Yolk mass increased with ambient temperature during laying, laying date, and the area of male black breast band. Lutein, zeaxanthin, and vitamin E increased with laying date. Total antioxidants increased with female age, immaculateness of female white cheek patch, and UV chroma of carotenoid-based yellow breast feathers of the social mate. These patterns were thus consistent with 1) environmental effects on yolk mass and composition, 2) higher quality females depositing more antioxidants, and 3) differential allocation of resources in females in relation to male ornamentation. Overall, environmental factors, female traits, and male traits all had an influence on egg yolk characteristics in this socially monogamous songbird.

Male barn swallows use different signalling rules to produce ornamental tail feathers

The evolution of secondary sexual characters is the subject of controversial debate between those defending their role as ‘viability indicators’ and those arguing that ornaments are purely ‘attractive traits’ selected by females. Recent theoretical studies suggest that these hypotheses are not mutually exclusive, as both viability and attractiveness can contribute to improve the reproductive success of progeny and could thus simultaneously underlie female choices. If that is the case, strategies of cheaper advertisement, allowing the expression of larger ornaments for the same cost, could proliferate even in species in which honest signalling of viability prevails. Under this scenario, different males could invest a different amount of resources per ornament unit of expression, thus using different signalling rules. We studied the relationship between tail feather length (a trait that is the subject of a female mate preference) and feather mass (a measure of investment in feather production) in a barn swallow Hirundo rustica population. Different males used different and consistent signalling rules when developing ornamental feathers. That is, to produce a feather of a given length, each male used a constant amount of resources across different years, but this amount varied between males. Although the amount of material invested in feathers (feather mass) is a condition-dependent trait, the organization of this material in ornamental feathers (i.e. the signalling rules) was not. Neither survival nor risk of feather breakage was related to the signalling rules. Thus, these results suggest that both ‘viability’ and ‘runaway’ mechanisms are independent determinants of the evolution of ornamental sexual feathers in the barn swallow. A preference for long tails will ensure that females either obtain a sire with high viability, or one transferring the capability to produce longer and more attractive tails at a lower cost of production to its offspring.

Female plumage coloration is sensitive to the cost of reproduction. An experiment in blue tits

1. A growing number of studies suggest that female ornaments are linked to maternal quality and influence male mate choice. These findings challenge the traditional male-biased view of sexual selection and the hypothesis that female ornaments are the outcome of a genetic correlation with male ornaments. To further test the hypothesis that female traits have a function, it is now essential to investigate their honesty and to determine how signalling and reproduction interact in females. If female traits are honest indicators of quality, then they are likely to have a specific signalling function. 2. We investigated whether carry-over effects of reproduction might ensure the honesty of plumage colour signalling of a bird species with conspicuous UV-blue and yellow coloration, the blue tit Cyanistes caeruleus. Reproductive effort was manipulated by removing clutches, thereby forcing both sexes to reproduce twice and to raise chicks later in the breeding season when food is less abundant. In the year following this manipulation, we investigated the change in plumage in experimental and control males and females. The change was measured in the two putative feather ornaments, the UV-blue cap and the yellow breast, and another feather trait probably less likely to be sexually selected: the wing length. We also tested whether higher-quality females had their coloration less affected by the experiment. 3. We found that control but not manipulated males and females increased their signal towards UV. In addition, in the manipulated group, females that were able to lay more eggs had their UV-blue coloration less affected by the treatment. For yellow coloration, we found that manipulated yearlings but not manipulated adults decreased their yellow chroma in comparison with control. Lastly, our results show that the condition of the manipulated females tended to be positively correlated with yellow chroma. 4. These results show that the trade-offs between reproduction and signalling can ensure the honesty of conspicuous plumage traits in female and male blue tits. In addition, they suggest that female traits have the potential to evolve under sexual selection in this and other bird species.

Yolk androgens in great tit eggs are related to male attractiveness, breeding density and territory quality

Females can adaptively adjust phenotype of their offspring via deposition of various compounds into eggs, including androgens and other hormones. Here, I investigated how egg yolk androgens (testosterone and androstenedione) related to environmental conditions and parental traits in the great tit (Parus major) across three breeding seasons. Male and female traits studied included age, condition and multiple feather ornaments, both carotenoid- and melanin-based (carotenoid and UV chroma of yellow breast feathers, area of black breast band and white cheek immaculateness). Yolk mass increased with laying temperature, laying date and area of male black breast band. Concentration of androgens increased with breeding density, territory quality and carotenoid chroma of male yellow breast feathers and was higher in mates of 1 year old as compared to older males. Yolk androgens were not related to any of the female traits analysed. These patterns were thus consistent with (1) social and environmental effects on yolk mass and composition and (2) both positive and negative differential allocation strategies of resource allocation in females. Overall, male traits were the most important predictors of egg yolk characteristics in this socially monogamous songbird.

Feather ornaments are dynamic traits in the Great Tit Parus major

In behavioural studies it has been common to quantify plumage colours or ornaments over a range of dates and link them to fitness characteristics without accounting for seasonal changes in these traits. Such changes are likely to be widespread among birds, yet we lack assessments of this variability within individuals. We studied both within‐ and between‐individual temporal changes in Great Tit Parus major ornaments, specifically the melanin‐based black breast stripe and the pigment‐free white cheek patch. During the non‐breeding season both ornaments varied. In juveniles and adult females, the area of the breast stripe first rose and then, from near the end of December, decreased. In adult males there was a linear decrease. In the cheek patch, the irregularity of the cheek borders showed either a linear (adults) or a non‐linear (juveniles) increase as the season progressed. In individuals repeatedly sampled during the same winter, the decrease in the size of the breast stripe was larger for males than females and there was an overall decrease in the regularity of the cheek borders. There was no relationship between the size of the breast stripe and the white cheek patch irregularities or the cheek patch area. These results imply that more attention should be paid to quantification, within individuals, of the components of expression of phenotypic traits. In addition, we suggest that further research should focus on explaining the causes and functions of ornament change.

Assessing the usefulness of ptilochronology in the study of melanin‐ and carotenoid‐based ornaments in the Great TitParus major

Ptilochronology is a method for assessing the nutritional condition of birds based on the width of daily growth bars on feathers. Wide growth bars reflect fast feather growth and as feather growth is costly, the width of the bars reflects the condition of a bird during moult (Grubb 1989). It is a very simple and inexpensive method, which makes it ideal for field research (Grubb 2006). In addition, as a sampled feather is soon replaced by a new feather, a process that would take place during natural moult, this method is also harmless to the bird. Ptilochronology has therefore become a popular method for assessing the nutritional state of birds in the wild (Grubb 2006). However, the efficacy of the method might differ, for example, between sexes (Grubb 1989, Takaki et al. 2001, Bostrom & Ritchison 2006) or age categories (Grubb et al. 1991). Kern and Cowie (2002) failed to find any relationship between the growth of different types of feathers taken from the same individual. Furthermore, other studies have concluded that the general validity of the method is unclear and that it can be used only under strictly controlled conditions (Murphy & King 1991). Despite these reservations, ptilochronology has been used in several studies of feather ornaments as an indicator of condition (Hill & Montgomerie 1994, Eeva et al. 1998, Keyser & Hill 1999, Doucet 2002, Senar et al. 2003, van Oort & Dawson 2005, Hegyi et al. 2007, Siefferman et al. 2008, Kimball 2009). The assumption is that these species moult body and contour feathers at the same time. Thus, if both ornaments and feather growth bars reflect condition (Griffith et al. 2006, Grubb 2006, Hill & McGraw 2006), then these two traits should covary. Carotenoid-based feather ornaments are expected to reflect a bird’s condition and there is evidence supporting this claim (von Schantz et al. 1999, Hill 2002, McGraw 2006a). Although melanin ornaments were thought not to reflect condition (McGraw 2006b), recent evidence suggests that they might be as condition-dependent as carotenoid-based ornaments (Griffith et al. 2006, Galvan & Alonso-Alvarez 2008). No clear-cut relationship between feather ornaments and feather growth has emerged from studies to date (see above). As ptilochronology is a very simple method and has great potential in field ornithology, we examined the relationships between both carotenoidand melaninbased ornaments and feather growth in a large sample of individuals of a wild passerine. We chose the Great Tit Parus major because expression of its carotenoid-based (Horak et al. 2000, Tschierren et al. 2003, but see Fitze & Richner 2002) and melanin-based ornaments (Fitze & Richner 2002, Galvan & Alonso-Alvarez 2008) is known to depend on condition during moult and feather growth. Thus, if feather growth also reflects condition during moult, we expected a positive correlation between the width of feather growth bars and the expression of both carotenoidand melanin-based ornaments.

Origin and maintenance of mechanosensory feather ornaments

Mechanosensory use is a seldom-mentioned function for feather ornaments, yet recent experimental evidence showed that the elaborate facial plumes of crevice-dwelling whiskered auklets, Aethia pygmaea, have just such a sensory role. Here we explored the evolutionary patterns of mechanosensory function of similar facial feather ornaments in related species. In an experimental chamber (maze) devoid of visible light, crested auklets, A. cristatella, a close relative of the whiskered auklet, showed an increase in head bumps (262%) after trial flattening of their forehead crest. The frequency of head bumps in the absence of the crest was positively correlated with the natural crest length of the crested auklet. There was no correlation between crest length and head bumps when we added an artificial crest to least auklets, A. pusilla, which do not have a natural crest. Thus, only the ornamented Aethia species that breed in deep-crevice appear to have detectable mechanosensory ability. A pairwise analysis across all nonpasserine bird families further revealed a greater frequency of elongated facial plumes in birds that live in complex habitats and are active during low light conditions. We suggest that selective pressure enforced by complex habitats may trigger facial feather exaggeration for mechanosensory use. Once the primordial sensory structures evolved, sexual and other social selection processes could act on these traits and lead towards further exaggeration.

André Thevet's ‘true’ portrait of Moctezuma and its European legacy

André Thevet's ‘true’ portrait of Moctezuma and its European legacy

Nestlings’ carotenoid feather ornament affects parental allocation strategy and reduces maternal survival

In some birds, feather ornaments are expressed in nestlings well before sexual maturation, possibly in response to parental favouritism towards high-quality offspring. In species with synchronous hatching, in which nestling ornaments may vary more among than within broods, parents may use this information to adjust their parental allocation to the current brood accordingly. We tested this hypothesis in the rock sparrow, in which a sexually selected yellow feather ornament is also expressed in nestlings. We experimentally enlarged nestlings' breast patch in a group of broods and sham-manipulated another group of control broods. Nestlings with enlarged ornament were fed more frequently and defended more actively from a dummy predator than their control counterparts. Mothers from the enlarged group were more likely to lay a second clutch and showed a reduced survival to the next breeding season. These results provide one of the first evidences of differential parental allocation among different broods based directly on nestlings' ornamentation, and the first, to our knowledge, to show a reduction in maternal survival.

Extra‐pair fertilizations contribute to selection on secondary male ornamentation in a socially monogamous passerine

Despite considerable research effort, it remains unclear whether extra-pair fertilizations (EPF) drive the evolution of male secondary ornamentation in socially monogamous systems. In this study, we test the hypothesis that EPF contribute to the evolution or maintenance of male feather ornamentation in a sexually dichromatic passerine, the Scarlet Rosefinch, Carpodacus erythrinus. We show that the colouration of ornamental breast feathers is a good predictor of basic sources of variation in male annual reproductive output in rosefinches and that the annual realized reproductive success of males is positively associated with measures of ornamental colouration only when gains and losses because of EPF are considered. The results indicate that EPF in rosefinches may rely on absolute (good genes) rather than self referential (genetic complementarity) criteria of mate choice. Our study corroborates the potentially important role of EPF in the evolution and/or maintenance of elaborate male ornaments in socially monogamous taxa.

The allometric pattern of sexually size dimorphic feather ornaments and factors affecting allometry

The static allometry of secondary sexual characters is currently subject to debate. While some studies suggest an almost universal positive allometry for such traits, but isometry or negative allometry for nonornamental traits, other studies maintain that any kind of allometric pattern is possible. Therefore, we investigated the allometry of sexually size dimorphic feather ornaments in 67 species of birds. We also studied the allometry of female feathers homologous to male ornaments (female ornaments in the following) and ordinary nonsexual traits. Allometries were estimated as reduced major axis slopes of trait length on tarsus length. Ornamental feathers showed positive allometric slopes in both sexes, although that was not a peculiarity for ornamental feathers, because nonsexual tail feathers also showed positive allometry. Migration distance (in males) and relative size of the tail ornament (in females) tended to be negatively related to the allometric slope of tail feather ornaments, although these results were not conclusive. Finally, we found an association between mating system and allometry of tail feather ornaments, with species with more intense sexual selection showing a smaller degree of allometry of tail ornaments. This study is consistent with theoretical models that predict no specific kind of allometric pattern for sexual and nonsexual characters.

A multifactorial test of the effects of carotenoid access, food intake and parasite load on the production of ornamental feathers and bill coloration in American goldfinches

It has been well established that carotenoid and melanin pigmentation are often condition-dependent traits in vertebrates. Expression of carotenoid coloration in birds has been shown to reflect pigment intake, food access and parasite load; however, the relative importance of and the potential interactions among these factors have not been previously considered. Moreover, carotenoid and melanin pigmentation have been proposed to signal fundamentally different aspects of individual condition but few data exist to test this idea. We simultaneously manipulated three environmental conditions under which American goldfinches (Cardeulis tristis) grew colorful feathers and developed carotenoid pigmentation of their bills. Male goldfinches were held with either high or low carotenoid supplementation, pulsed or continuous antimicrobial drug treatment, or restricted or unlimited access to food. Carotenoid supplementation had an overriding effect on yellow feather coloration. Males given more lutein and zeaxanthin grew yellow feathers with hue shifted toward orange and with higher yellow chroma than males supplemented with fewer carotenoids. Parasites and food access did not significantly affect yellow feather coloration, and there were only minor interaction effects for the three treatments. By contrast, bill coloration was significantly affected by all three treatments. Carotenoid supplementation had a significant effect on yellow chroma of bills, drug treatment and food access both had a significant effect on bill hue, and food access had a significant effect on the yellow brightness of bills. Neither the size nor blackness of the black caps of male goldfinches was affected by any treatment. These results indicate that pigment intake, food access and parasite load can have complex and variable effects on color displays, and that feather and bill coloration signal different aspects of male condition.

Male barn swallows use different resource allocation rules to produce ornamental tail feathers

Sexual ornaments compete for resources with other functional traits. Such resource allocation trade-offs should ensure the honesty of sexual ornaments according to the Zahavi’s handicap principle. However, the existence of costly signals could not be enough to guarantee honesty if different individuals invest different proportions of their limited resources in ornaments. Then, a certain level of sexual signaling would correspond to several levels of individual condition. Here, we explore whether there are different resource allocation rules in tail feather ornaments between males within a barn swallow (Hirundo rustica) population and whether these different rules confer different viability to males. We assessed the proportion of resources invested in ornamental feathers compared with other functional feathers moulted and growing during the same period at expenses of the same resources. We found that 1) different males allocate a different proportion of resources to ornamental feathers in relation to functional feathers and this proportion is repeatable between years and 2) male survival likelihood decreased as the proportion of resources allocated to ornamental feathers increased. Survival costs associated with increased investments in ornaments can maintain the sexual signaling system honest at population level but do not preclude the existence of an array of different allocation rules between males. Thus, males with different viability can produce ornamental feathers of the same length. These results show that the relationship between male viability and ornament expression can be less straightforward than considered previously. Key words: barn swallow, honesty, resource allocation, sexual ornaments, tail feathers, tradeoff. [Behav Ecol]

Mechanosensory function for facial ornamentation in the whiskered auklet, a crevice-dwelling seabird

Sexual selection has been the prevalent explanation for the evolution of birds’ elaborate feather ornaments. An overlooked possibility is that feather appendages arose due to a naturally selected sensory function involving sensitivity to pressure or touch to facilitate obstacle avoidance either in flight or on land. Here, we show experimentally that elongated facial feather adornments of whiskered auklets (Aethia pygmaea), a sexually monomorphic crevice-dwelling seabird, have a mechanosensory use for orientation in darkness underground. While navigating inside a lightproof maze simulating the structure and conditions of breeding crevices, whiskered auklets (n = 99) showed a 275% increase in frequency of head bumps in the absence of their protruding feather crest and facial plumes. A weak positive relationship (R = 0.36, P = 0.04) between natural crest length and the frequency of head bumps in the absence of the crest suggested that individuals with longer ornaments depend more on these traits for navigation in the wild. We hypothesize that protruding feathers evolved through a combination of natural selection for sensory function and sexual selection as known for other auklets. More widely, birds inhabiting cluttered environments would benefit from elongated facial plumage that mechanically detects obstacles. Key words: Aethia, feather ornaments, mechanosensory function, sexual selection, whiskered auklet. [Behav Ecol]

Moult speed constrains the expression of a carotenoid‐based sexual ornament

We investigated the effect of moult speed on the expression of a sexually selected, carotenoid-based feather ornament in the rock sparrow (Petronia petronia). We experimentally accelerated the moult speed of a group of birds by exposing them to a rapidly decreasing photoperiod and compared the area and the spectral characteristics of their ornaments with those of control birds. Birds with accelerated moulting rate showed a smaller yellow patch with lower yellow reflectance compared to their slow-moulting counterparts. Considering that the time available for moulting is usually constrained between the end of the breeding season and migration or wintering, carotenoid feather ornaments, whose expression is mediated by moult speed, may convey long term information about an individual's condition, potentially encompassing the previous breeding season. Furthermore, the observed trade-off between moult speed and ornament expression may represent a previously unrecognized selective advantage for early breeding birds.

Developmental evolution of sexual ornamentation: model and a test of feather growth and pigmentation

A tremendous diversity of avian color displays has stimulated numerous studies of natural and sexual selection. Yet, the developmental mechanisms that produce such diversification, and thus the proximate targets of selection pressures, are rarely addressed and poorly understood. In particular, because feathers are colored during growth, the dynamics of feather growth play a deterministic role in the variation in ornamentation. No study to date, however, has addressed the contribution of feather growth to the expression of carotenoid-based ornamentation. Here, we examine the developmental basis of variation in ornamental feather shapes in male house finches (Carpodacus mexicanus)-a species in which carotenoid displays are under strong natural and sexual selection. First, we use geometric morphometrics to partition the observed shape variation in fully grown feathers among populations, ages, degrees of elaboration, ornamental body parts, and individuals. Second, we use a biologically informed mathematical model of feather growth to predict variation in shape of ornamental feathers due to simulated growth rate, angle of helical growth of feather barbs, initial number of barb ridges, rate of addition of new barbs, barb diameter, and ramus-expansion angle. We find close concordance between among-individual variation in feather shape and hue of entire ornament, and show that this concordance can be attributed to a shared mechanism-growth rate of feather barbs. Predicted differences in feather shape due to rate of addition of barbs and helical angle of feather growth explained observed variation in ornamental area both among individuals and between populations, whereas differences in helical angle of growth and the number of barbs in the feather follicle explained differences in feather shape between ornamental parts and among males of different ages. The findings of a close association of feather growth dynamics and overall ornamentation identify the proximate targets of selection for elaboration of sexual displays. Moreover, the close association of feather growth and pigmentation not only can reinforce condition-dependence in color displays, but can also enable phenotypic and genetic accommodation of novel pigments into plumage displays providing a mechanism for the observed concordance of within-population developmental processes and between-population diversification of color displays.

NAMED SUBSPECIES AND THEIR SIGNIFICANCE IN CONTEMPORARY ORNITHOLOGY

Subspecies, or geographic races, are diagnosable populations that, at least during the breeding season, are largely allopatric with other subspecies of the same species. In attempts to give objectivity to the subspecies concept, arbitrary rules have been applied for the recognition of subspecies (e.g., the rule/' whereby of the individuals should be identifiable to subspecies; there are several other rules). As a case study, I examined the usefulness of the subspecies concept in describing geographic variation of a polytypic American songbird, the Savannah Sparrow (Passerculus sandwichensis). About 21 subspecies of this species have been recognized in the taxonomic literature, but much of the geographic variation is clinal. I argue that there is little value in subdividing a clinal continuum into different subspecies. Rather, the use of subspecies is best restricted to distinctive, and usually geographically isolated, populations. I show that this has been done for only a few of the named subspecies of Savannah Sparrows. Received 31 July 2006, accepted 6 March 2007. Resumen.Las subespecies, o razas geograficas, son poblaciones generalmente alopatricas (al menos durante epoca de reproduction) y que se pueden diferenciar claramente de otras subespecies de misma especie. Se han propuesto diferentes reglas para asignar individuos a una determinada subespecie, e.g. la regla del 75% (75% de los individuos tienen que ser identificables como subespecie), en un intento de dar objetividad al concepto de subespecie. Como caso de estudio, discuto utilidad del concepto de subespecie para describir variacion geografica de Passerculus sandwichensis. Se han reconocido cerca de 21 subespecies, pero gran parte de variation geografica es clinal. Argumento que es de poco valor el subdividir una clina continua en subespecies diferentes. Se debe restringir el uso de subespecies para poblaciones bien diferenciadas y aisladas geograficamente. Muestro que esto se ha hecho solo para unas pocas de las subespecies de Passerculus sandwichensis. In recent years, many biologists have used intraspecific geographic variation to test hypotheses about adaptation and evolution, and named subspecies have reflected this variation. For example, M0ller and Cuervo (1998) compared feather ornamentation in birds to test the hypothesis that sexual selection promotes speciation and found that ornamented species had more subspecies than non-ornamented specieswhich suggests an association between subspeciation and ornamentation. Likewise, Sol et al. (2005) examined brain size relative to body size in Holarctic passerines, to test the hypothesis that behavioral changes are an important ^-mail: rising@zoo.utoronto.ca driver of evolutionary diversification, and found that species with large relative brain size have undergone more extensive subspecific diversification. It is clearly important for these studies that named subspecies more or less accurately reflect units of intraspecific diversification. Wilson and Brown (1953) identified several problems with the subspecies concept as then applied. Among these was the arbitrary lower limit of the distinctiveness of subspecies (i.e., how distinctive must a population be to earn a subspecific trinominal name?). There are several arbitrary rules, the most common being the rule (Amadon 1949), though efforts have been made to apply more rigorous diagnosability rules to the classification of subspecies (e.g., Patten and Unitt 2002, Remsen 2005, Cicero and

Armaments and ornaments in the rock sparrow: a possible dual utility of a carotenoid-based feather signal

Females often base their mating preferences on male sexual secondary traits that are used to settle contests among males. Such traits are likely to be honest indicators of male quality if they are constantly used during costly male–male agonistic interactions. Carotenoid signals have been shown to work as a handicap because they are costly to produce. However, the role of carotenoids as “honest” signals during male contests is less clear, and it is not known whether a carotenoid-based trait can serve in both male–male competition and female choice. In this study, we studied the dual function of a carotenoid feather ornament in the rock sparrow (Petronia petronia), a bird species in which both sexes have a yellow throat patch whose size positively correlates with phenotypic measures. First, we investigated, in a field study, whether the size of a male’s yellow patch correlates with his ability to acquire a territory. Second, we tested the signal function of the yellow patch in two male–male interaction in captivity experiments. Finally, we measured female preference for males differing in throat patch size in a mate choice experiment. Our experiments revealed that the size of a male’s throat patch positively correlated with the number of nest boxes he was able to defend. Moreover, in controlled conditions, males with relatively large yellow patches had earlier access to food than those with small patches. Also, in an experiment in which a dummy rock sparrow with an experimentally manipulated yellow patch was positioned near a feeder, latency to feed by focal birds positively correlated with dummy patch size. Lastly, in a dichotomous mate choice experiment, females showed a proximity preference for males whose patch was experimentally enlarged. Taken together, these results suggest that the same carotenoid feather signal may be used in both male–male competition and female choice in this passerine bird.

The Jivaro shrunken heads from the National Museum , Rio de Janeiro, Brazil. Authentic or Counterfeits?

The Jivaro people from Ecuador, Amazonia, skillfully mummified human heads by shrinking them to the size of a fist. The Jivaro became famous as the Amazonian headhunters. This mummification was practiced in the context of a ritual in which individuals developed more and more spiritual power supported by the submission of their enemy souls. In the original ritual the heads were discarded or “buried” in the rivers. Historical contacts and religious conversion prohibited the practice and only a few shrunken heads can be found in museums today. Six Jivaro shrunken heads, probably from adult men with ornaments including a Caucasian, are described in this presentation. Some of them date to the 19th century, and were acquired by the Brazilian emperor. The discovery of nits and eggs of Pediculus humanus in those mummified scalps makes their description still more interesting. Cultural details like feather ornaments, hair styles, cordage, and other characteristics are discussed