Throat Patch Research Articles

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.

Divergent roles for multiple sexual signals in a polygynous lizard

Summary An unresolved issue in sexual selection concerns the utility of multiple sexual signals that are used simultaneously during displays. We examined male lizards (Urosaurus ornatus) that exhibit two colourful ornaments (throat patch and belly patch) during territorial displays. Populations of Urosaurus ornatus can be polymorphic in throat coloration, and previous studies have shown that the morphs differ in behavioural aggression. We assume that throat coloration correlates with behavioural aggression in our population, as for other populations of U. ornatus. We show that these different morphs do not differ significantly in morphological shape or bite force, a key aspect of fighting capacity. However, by contrast, the size of the belly patch is a significant predictor of maximum bite force, which is a predictor of dominance in other lizards. We suggest that belly patch size and throat patch coloration are largely exclusive in that dominant individuals can exhibit small belly patches and low bite forces, whereas subordinate individuals can have large belly patches and high bite forces. Thus, embedded within the same male lizard display are divergent sexual structures that signal different traits, implying that the possession of multiple sexual signals within animals may be favoured by selection.

Female-specific color is a signal of quality in the striped plateau lizard (Sceloporus virgatus)

Recent theoretical and empirical studies confirm that male mate choice and/or female--female mate competition can be expressed in the absence of sex-role reversal. Such reproductive patterns may select for the evolution of female traits that indicate female phenotypic or genotypic quality among non--role-reversed species. Although attention to the evolution and function of female ornaments is increasing, additional focus is needed on female-specific ornaments (those not expressed in conspecific males) and on nonavian systems in order to gain a broad understanding of how selection acts directly on ornamentation of female animals. In the striped plateau lizard, Sceloporus virgatus, only females develop orange throat patches during the reproductive season. The color peaks in expression near the time of ovulation and appears to stimulate male courtship. Here, I examine whether this female-specific ornament can be used by males to reliably assess female phenotypic quality. Using multivariate regression analyses, I show that the area of the orange color patch predicts body condition and mite load, the chroma (i.e., saturation) of the color patch predicts body size, and both patch area and chroma reliably predict average egg mass. Thus, female reproductive color may function as a condition-dependent signal, indicating phenotypic quality to potential mates. Copyright 2006.

IMPORTANCE OF FACIAL PATTERN TO SEXUAL SELECTION IN GOLDEN-WINGED WARBLER (VERMIVORA CHRYSOPTERA)

Abstract The importance of the black facial pattern in sexual selection in Golden-winged Warblers (Vermivora chrysoptera) was evaluated through experimental plumage modification. We lightened the throat patch and eye mask with hair bleach, which essentially created artificial Brewster's Warbler (F1 generation of Golden-winged Warbler × Blue-winged Warbler [V. pinus]) plumage phenotypes. Experimental males lost their original territories and failed to obtain mates. We concluded that there is sexual selection against the Brewster's facial pattern. Sexual selection attributable to the face pattern may explain the apparent greater effect of hybridization on Golden-winged Warblers than on Blue-winged Warblers. Importancia del Patron Facial en la Seleccion Sexual de Vermivora chrysoptera

Female throat ornamentation does not reflect cell-mediated immune response in bluethroats Luscinia s. svecica

The brilliantly coloured throat patch in male bluethroats, Luscinia s. svecica, influences their social mating success and both within- and extra-pair paternity. Female bluethroats are highly variable in their extent of throat coloration, from entirely drab to almost male-like. The ornament in females could be due to a genetic correlation between the sexes. However, it has been shown that male bluethroats prefer brightly coloured females, suggesting that female ornamentation has evolved by direct sexual selection on females through male choice. Males may prefer extravagant traits in females if these reliably signal female quality, such as resistance to disease. We investigated whether variation in the extent of structural and melanin plumage ornamentation in female bluethroats reflects cell-mediated immune response. We caught the females at their nests and measured their immune response as a swelling following a challenge by phytohemagglutinin. An analysis of the data from two years of study revealed that the cell-mediated immune response was not related to female ornamentation. However, the immune response was strongly correlated with female body condition. Thus, our results do not support the hypothesis that female ornament expression signals quality in terms of cell-mediated immunity.

Yolk testosterone organizes behavior and male plumage coloration in house sparrows (Passer domesticus)

Vertebrate eggs contain maternal steroid hormones in their yolks; and in avian species the concentration of these steroids vary within and among clutches. The organizational actions of these variable doses of maternal steroids in the avian egg, analogous to those regulating the development of sexually dimorphic traits, are little explored. In this study, we examined the organizational effects of yolk testosterone in the house sparrow, Passer domesticus, a sexually dichromatic passerine bird in which males are characterized by the presence of a throat patch or “badge” of black feathers that varies in size among males. We injected a physiological dose of testosterone or vehicle into eggs in the field, removed nestlings, and hand-raised them in the laboratory. At 5 months of age, we investigated treatment effects on plumage and behavior. Males that hatched from testosterone-injected eggs developed a larger badge than males that hatched from vehicle-injected (control) eggs. However, testosterone did not induce the expression of a badge in females. In staged dyadic encounters, both males and females hatched from testosterone-injected eggs were more successful at obtaining and defending a food source than individuals of the same sex hatched from control eggs. The results suggest that variable concentrations of maternal testosterone in the eggs of the house sparrow organize the expression of a plumage trait in males and behavior in both sexes.

Voice Breaking in Males Results in Sexual Dimorphism of Green Woodhoopoe Calls

Summary Ontogenetic changes and sexual differences in the acoustic structure of green woodhoopoe (Phoeniculus purpureus) ‘kek’ calls were investigated in a wild population. At fledging, the calls of males and females were indistinguishable in terms of fundamental frequency, frequency modulation, peak frequency and call duration. After 3-5 months, however, the male voice ‘broke’ (i.e. underwent a significant decrease in fundamental frequency), while there was no change in female call structure. Consequently, the fundamental frequency of adult male calls was 48% lower than that of adult females, and there was no overlap in the call frequencies of the sexes in adulthood. The change in male voice occurred within a 23 week period and no intermediate call frequencies were recorded. The timing of the voice break did not correspond with a change in overall body size, suggesting that growth of the syrinx was not the proximate cause. However, it did coincide with the stage in development when male bill length grew to exceed that of all females and when males began to lose their distinctive brown throat patch, providing some indirect evidence that hormonal control may be important.

Sex of opponent influences response to a potential status signal in house sparrows

We evaluated the possible use of a sexually dimorphic plumage trait as a status signal in inter- and intrasexual social interactions in free-living house sparrows, Passer domesticus. Males with larger black throat patches (bibs) tended to be dominant regardless of the opponent's sex. This relationship was maintained after controlling for body size and age in multivariate analyses. However, the nature of social interactions varied according to the sex of the opponent and a male's bib size. Males with larger bibs tended to be less aggressive to male opponents, and received significantly less aggression from those birds, a key predicted benefit of a status signal. However, when the opponent was a female, males with large bibs displayed significantly more aggression than males with small bibs, and this relationship persisted even after controlling for the dominance status of the participants. Females were significantly more aggressive towards male opponents than towards female opponents, and females interacting with two males of known bib size were more aggressive to the one with the larger bib. These results suggest that the bib of male house sparrows may be a signal of status, but that in interactions with females, the bib may also have other functions. Frequent testing by females of the underlying quality being signalled by the bib may be linked to later mate choice, and might be adaptive if the information value of the bib varies among years. Such testing may also contribute to mechanisms for maintaining the bib as a reliable signal of status. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.

Carotenoid status signaling in captive and wild red-collared widowbirds: independent effects of badge size and color

Carotenoid-based plumage ornaments are typically considered to be sexually selected traits, functioning as honest condition-dependent signals of phenotypic quality, but few studies have addressed the function of carotenoid color variation in male contest competition. Using two experiments, we investigated the status signaling function of the variable (ranging from yellow to red) carotenoid throat patch (collar) in the polygynous, sexually dimorphic red-collared widowbird (Euplectes ardens). First, we tested if the red collar functions as a dominance signal by painting spectrometrically controlled collar patches onto the brown plumage of nonbreeding males and staging dyadic male contests over food resources. Red-collared males dominated orange males, which in turn dominated the control brown and novel blue collars. Red dominance persisted when the collar manipulations were reversed within dyads and also when tested against testosterone implanted males. In the second experiment the collar size and color of breeding males were manipulated in the field before and after territories were established. All males with enlarged red and most with enlarged orange or reduced red collars obtained territories, whereas most males with reduced orange and all with blackened (removed) collars failed to establish or retain territories. In addition, among the territorial males, those with reduced signals defended smaller territories, received more intrusions, and spent more time in aggressive interactions. Redness and, to a lesser extent, size of the carotenoid ornament both seem to independently indicate male dominance status or fighting ability in male contest competition. Copyright 2002.

Badge size, paternity assurance behaviours and paternity losses in male house sparrows

Male quality may influence both the outcome of sperm competition and female faithfulness. In male house sparrows Passer domesticus, the size of the black throat patch (badge) signals dominance and perhaps attractiveness. So far, however, no study has reported any significant relationships between badge size, paternity and paternity assurance behaviours in this species. We found that the time mates spent together at the nest was positively correlated with badge size. Furthermore, although paternity losses were influenced by both the time spent at the nest and within‐pair copulation frequency, we found no relationship between copulation rate and badge size. It seems therefore that copulation frequency served as a paternity assurance behaviour, whereas the time mates stayed together at the nest may have reflected male attractiveness. Alternatively, females may have decided to stay with large‐badged males because they were better able to protect them from harassment by strange males. We also found that paternity losses were related to male badge size; average‐badged males cuckolded were more often than males with smaller or larger badges. We suggest that average‐badged males suffered higher paternity losses because they had different time allocation strategies than other males.

The Role of Nuptial Coloration in Female Holbrookia maculata: Evidence for a Dual Signaling System

The Role of Nuptial Coloration in Female Holbrookia maculata: Evidence for a Dual Signaling System

Is male plumage reflectance correlated with paternal care in bluethroats?

Although it is now well established that the conspicuous male plumage colors of many birds have been subject to sexual selection by female choice, it is still debated whether females mate with colorful males to obtain direct or indirect benefits. In species where males provide substantial parental care, females may obtain direct benefits from mating with the males that are best at providing care. The good parent hypothesis suggests that male plumage coloration signals a male’s ability to provide parental care. Alternatively, the differential-allocation hypothesis suggests that colorful males reduce their care in response to increased investment by females mated to attractive males. We tested these hypotheses on the bluethroat (Luscinia s. svecica), a socially monogamous, sexually dichromatic bird, in which males have a colorful throat patch consisting of a structurally derived blue area surrounding a melanin-based chestnut spot. Male plumage coloration was objectively quantified by use of reflectance spectrometry. We found no evidence of a relationship between male coloration of either the blue patch or the chestnut spot and the level of paternal care. Nor were there any correlations between male coloration and body size or body condition. Thus, our study does not support the hypothesis that male coloration signals male parental quality (the good parent hypothesis) or the hypothesis that colorful males reduce their care in response to increased investment by females (the differential-allocation hypothesis). Key words: direct benefits, female choice, Luscinia s. svecica, parental care, plumage coloration, sexual selection, spectral reflectance. [Behav Ecol 12:164–170 (2001)]

Does female plumage coloration signal parental quality? A male removal experiment with the bluethroat ( Luscinia s. svecica )

Females in several sexually dimorphic species with conventional sex roles possess ornamental traits that resemble those found in males. The evolution of such traits, however, is still poorly understood. Bluethroats (Luscinia s. svecica) are socially monogamous, sexually dichromatic passerine birds, in which female throat patch coloration varies from near absence to near full expression of male-like coloration. A recent study, demonstrating that male bluethroats prefer colourful females, suggests that female coloration is subject to sexual selection through male choice. However, the benefits males may gain from mating with colourful females have not yet been identified. In this study we tested the hypothesis that female coloration signals parental quality (the good-parent hypothesis). During the course of the same day, we recorded female care both in the presence and the absence of the male mate. The latter was done to eliminate the confounding effect of variable male care by removing the male temporarily. Female coloration did not correlate with female feeding rates either in the presence or in the absence of the male. Female feeding rates in the absence and the presence of the male were positively, although weakly, correlated. Female coloration did not correlate with female ability to compensate for the loss of male care, or with the change in brood mass during male removal. Therefore, there is no evidence for the good-parent hypothesis to explain female plumage coloration in bluethroats.

Reproctive and post-reproductive hormone levels in the lizard Sceloporus virgatus

Los niveles plasmáticos de seis hormonas (estradiol, progesterona, testosterona, dihidrotestosterona, androstenediona y corticosterona) en machos y hembras de Scehporus virgatus (Phrynosomatidae) fueron obtenidos durante y después de la temporada alta de apareo. Se encontró variación en los niveles hormonales relacionados con la temporada de la actividad reproductiva. Las hembras tuvieron un nivel de corticosterona más alto en agosto (después de la oviposición) que en abril (inmediatamente después de la eclosión), mientras que en los machos el nivel fue más bajo en agosto. La variación basal de la corticosterona podría reflejar diferencias sexuales en la época de máximo estrés fisiológico. Los machos presentaron altos niveles de las hormonas androgénicas en los meses de abril y mayo, coincidiendo con la temporada alta de apareo. Muchas lagartijas de la familia Phrynosomatidae muestran coloración ventral durante los despliegues sociales. En algunas especies de lagartijas se han reportado influencias androgénicas sobre esta coloración ventral. Tanto los machos como las hembras de S. virgatus presentan una gran reducción en la cantidad e intensidad de la mancha azul en la parte ventral en comparación con otras especies del mismo género. Sin embargo, la variación en el tamaño y brillo de la mancha azul, en la parte ventral del cuello, no está relacionada con la variación de ios niveles hormonales. Los niveles máximos de testosterona en los machos de S. virgatus son similares a los encontrados en otras especies de Sceloporus con manchas azules más grandes y brillantes.

On the function of female ornaments: male bluethroats prefer colourful females

Female ornaments in animals with conventional sex roles have traditionally been considered non–functional, being merely a genetically correlated response to selection for male ornamentation. Alternatively, female ornaments may be influenced by selection acting directly on the females, either through female–female competition or male choice. We tested the latter hypothesis in mate choice experiments with bluethroats ( Luscinia s. svecica ), a passerine bird in which females vary considerably in coloration of an ornamental throat patch. In outdoor aviaries placed in prime breeding habitat, males were allowed to choose between a colourful and a drab female. We found that males associated more with, and performed more sexual behaviours towards, colourful females. Female coloration was not age–related, but correlated significantly with body mass and tarsus length. Thus, we have demonstrated both a male preference for female ornamentation, and a relationship between ornament expression and female body size, which may be indicative of quality. Our results refute the correlated response hypothesis and support the hypothesis that female ornamentation is sexually selected.

Female bluethroats prefer males with symmetric colour bands

Fluctuating asymmetry in male ornaments may be related to male quality and therefore may be used by females as a guide in mate choice. Experiments on different species have shown female preferences for symmetry, but few previous studies have addressed preferences for symmetry in coloration. Using the bluethroat,Luscinia s. svecicaa passerine with a conspicuous blue and chestnut throat patch, as a model species, we devised an experiment in which the females could choose between males with either symmetric or asymmetric coloured leg bands. The females associated more with symmetric than asymmetric males, indicating a preference for symmetry.

Permanent exposure versus facultative concealment of sexual traits: an experimental study in the house sparrow

In many bird species the cryptic winter plumage is due to the presence of light feather tips that conceal conspicuous colorations. The gradual abrasion of these tips that makes sexual traits visible has been interpreted as a strategy to improve mating success (here referred as the permanent exhibition hypothesis). However, under some circumstances, the maintenance of a full plumage that facultatively enables the bird to exhibit or cover aggression-inducing traits has proved to be advantageous (the coverable badge hypothesis). In a population of house sparrows where black throat patches (here called badges) are used in intrasexual competition, the degree of abrasion of dull feather tips that conceal bright colour early in the breeding season correlated neither with badge size nor with traits indicating morphology and body condition. These results are only in accordance with predictions of the coverable badge hypothesis. In 1992 experimental clipping of badge feather tips, which forced permanent exposure of badges, negatively affected birds with the largest badges in terms of nest acquisition, but an opposite trend was indicated for birds with the smallest badges. In 1993, when more novel birds in the study area were competing for nesting sites than in 1992, only badge size, but not the experimental manipulation, affected nesting success. These results suggest that the loss of the ability to conceal badges was disadvantageous, and more so if most competing individuals had already been resident in the colony in previous years and the larger their badges were. There is a striking contrast between the results reported for this study population, where badges mainly signal fighting ability, and those reported for another house sparrow population, where badges are mainly used in mate choice. In this last population, tip abrasion is advantageous for dominant individuals showing the largest badges. This suggests that the trade-off between conserving versus wearing off the feathers that conceal ornaments could have different optimal resolutions depending on the relative importance of inter and intrasexual selection on indicator traits.

A critical period for the organization of alternative male phenotypes of tree lizards by exogenous testosterone?

Male tree lizards ( Urosaurus ornatus) exhibit permanent adult differences in color and size that are functionally linked with behavioral differences: males with a central blue throat patch are territorial, more aggressive, and smaller than males lacking the patch, who are nomads or satellites foregoing territory defense. Gonadectomy or long-lasting hormone implants in hatchlings affect the development of these permanent adult differences, but similar manipulations in adults are ineffective. Analogous early hormone actions in vertebrate sexual differentiation typically must occur during a critical period. Whether there is a critical period for early hormone actions affecting development of male types in tree lizards is unclear. We followed a protocol identical to our previous experiments on hatchlings, but we manipulated testosterone (T) in later-aged juveniles to determine if they remained sensitive to such hormone manipulations. Testosterone implants given at 60 days posthatching (day 60) did not alter adult throat color, indicating that sensitivity of throat color to T declines by day 60. This contrasts to our earlier work where adult color was affected by T manipulations on day 30. However, size and throat color responded differently to exogenous T, as juveniles given T implants at day 60 grew less than control-implanted males.

Unattractive Males Guard Their Mates More Closely: an Experiment with Bluethroats (Aves, Turdidae: Luscinia s. svecica)

AbstractMate guarding by close following is assumed to function as a paternity guard in pair‐bonding birds. Although this behaviour has been described for many species, little is yet known about the variation in mate‐guarding intensity between males in a population and the reason for such variation. In this study, we wanted to examine how mate‐guarding intensity relates to the sexual attractiveness of the male. Male bluethroats, Luscinia s. svecica, have a bright throat patch, an ornament extensively displayed during courtship. Two experiments are reported. In the first, we show that males which had their throat patch blackened (with Nyanzol D) before pairing had a lower pairing success than control males. We conclude that the blackening of the throat patch reduced male attractiveness. In the second experiment, a group of males were blackened after pairing. These males guarded their mates more closely than did control males, and spent less effort advertising for secondary mates. Thus, we conclude that a male's mate‐guarding intensity is flexible and negatively related to his sexual attractiveness. The mechanisms by which a male can assess the likelihood of becoming cuckolded are discussed.

Nuptial Colour Loss and Signal Masking in Gasterosteus: an Analysis Using Video Imaging

Threespine stickleback vary greatly in male nuptial display, from full red expression between the throat and pelvis to total melanism without any traces of red. The dominant expression for any population is correlated with the underwater spectral irradiance and many populations with melanistic nuptial colour occur in bog habitats where the aquatic spectrum is shifted to long wavelengths. Field observations indicate that in these bog habitats, the typical red nuptial signal is 'spectrally masked' and this might reduce the effectiveness of display during male-male and male-female interactions. We used video imaging techniques to test whether the spectral composition of the visual background influences female preference for nuptial colouration in male threespine sticklebacks. Throat colour preference tests were carried out in which females chose between video images of red and black-throated males superimposed on either a blue or a red background. Despite belonging to a red-throated population, females were found to respond preferentially to the black-throated male image viewed against a red background, indicating that preference was not determined by throat patch hue. This suggests that preference for an epigamic optical signal is likely a function of its efficacy in generating visual contrast rather than its intrinsic spectral characteristics.