Delayed Plumage Maturation Research Articles

Is plumage darkness in the North Island robin (Petroica longipes) mediated by aggression?

The extent of darkening of melanin‐based plumages in birds has previously been linked with increasing aggressive encounters between individuals. The North Island robin (Petroica longipes) is a territorial New Zealand endemic passerine that displays delayed plumage maturation (darkening of the plumage with age). Aggressive boundary interactions in the robin are relatively common during the breeding season, when territories are protected and juveniles are dispersing. This study tests the hypothesis of aggression‐mediated plumage darkening in a population of North Island robins by examining if males and older (darker) birds are either (1) involved in a higher number of aggressive interactions, or (2) are more often the aggressor than females and younger birds. When sex and age are accounted for, darker individuals will be either (3) involved in a higher number of interactions or (4) more often the aggressor in encounters with other individuals. Data were collected by scoring the plumage darkness of 32 individuals in the field, and observing (1) interaction behaviours, and (2) age and sex of the birds involved in each interaction. The results show no support for any aggression‐mediated plumage darkness in the robin; males and older birds were not involved in more aggressive interactions, and were not more often the aggressor; and neither the frequency of interactions or the number of aggressive interactions were correlated with a darker plumage. Other more complex mechanisms may explain delayed plumage darkness in the North Island robin.

Delayed plumage maturation in Eurasian kestrels: female mimicry, subordination signalling or both?

Delayed plumage maturation (DPM) of young males in sexually dichromatic birds has been explained under the female mimicry hypothesis (FMH) or the subordination signalling hypothesis (SbSH), among other adaptive ideas proposed. In this study, we tested in the Eurasian kestrel, Falco tinnunculus, the predicted sexual deception and aggressiveness under the FMH and SbSH to explain DPM in birds. We analysed aggressive and courtship behaviour of breeding males and females in the presence of adult male, adult female and 1-year-old male natural decoys. We designed two different treatments: one presenting un-moulted 1-year-old males and a second presenting partly moulted 1-year-old males, as observed in nature. Males attacked adult male decoys more frequently than 1-year-old male and female decoys in both moulted and un-moulted treatments and no sexual displays were observed. Females were more aggressive towards female and 1-year-old male decoys as compared to male decoys in the un-moulted treatment. In the moulted treatment, females were more aggressive towards female decoys as compared to both male decoys. In addition, females solicited copulas from moulted, but not from un-moulted, 1-year-old male decoys. Our results suggest that FMH can be a mechanism which explains DPM in un-moulted 1-year-old males. However, when they show moulted plumage (more than 80% in the studied population during the spring), the SbSH seems to be the mechanism that better explains sexual and agonistic behaviour from adults towards 1-year-old males.

Ornamental colors reveal age in the king penguin

We investigated whether delayed plumage maturation occurred in king penguins (Aptenodytes patagonicus). Therefore we examined the relationships between age and sex on spectral properties and size of two colored plumage patches and a UV-reflective beak spot, using known-age cohorts. Unlike the colored patch on the breast, we found age differences in ear and beak coloration. These results suggest that head ornaments in king penguins could signal sexual maturity or social status. No sex differences were found in the intensity of colored ornaments, which can result from mutual mate choice or genetic correlation between sexes. Size of colored patches did not relate to age or sex.

Is the later arrival of young male red-breasted flycatchers (Ficedula parva) related to their physical condition?

Intraspecific variation in the arrival time of migratory birds to breeding grounds is common. Although this phenomenon has been explained in various ways, the condition-dependency of arrival is often evoked. I analyzed the arrival time of male red-breasted flycatchers Ficedula parva, a long-distance migratory passerine, in relation to age, body size and body condition. Data were collected over the course of 5 years in the primeval Bialowieza Forest of northeast Poland. Each of these years, young males arrived at the breeding grounds significantly later in the year than did older males. Young males also exhibited significantly shorter wings and lower body condition than older males. Settlement speed was significantly related to age, but not to wing length or body condition. Only the arrival time of old males was related to the body mass and condition. Later arrival of young males could be explained by the lack of experience or by avoidance of both aggression and competition from older males, and both explanations are thought to conserve energy for breeding. Young male red-breasted flycatchers exhibit delayed plumage maturation, and this duller plumage supports the strategy of restraint in the arrival time of young males in this species.

Plumage Development and Molt in Long-Tailed Manakins (Chiroxiphia Linearis): Variation According to Sex and Age

AbstractLek-mating Long-tailed Manakins (Chiroxiphia linearis) exhibit an unusual pattern of delayed plumage maturation. Each year, males progress through a series of predefinitive plumages before attaining definitive plumage in their fifth calendar year. Females also exhibit variation in plumage coloration, with some females displaying male-like plumage characteristics. Using data from mist-net captures in northwest Costa Rica (n = 1,315) and museum specimens from throughout the range of Long-tailed Manakins (n = 585), we documented the plumage sequence progression of males, explored variation in female plumage, and described the timing of molt in this species. Males progressed through a series of age-specific predefinitive plumages, which enabled the accurate aging of predefinitive-plumaged males in the field; this predefinitive plumage sequence is the basis for age-related status-signaling in these males. Females tended to acquire red coloration in the crown as they aged. However, colorful plumage in females may be a byproduct of selection on bright male plumage. Females exhibited an early peak of molt activity from February to April, little molt from May through July, and a second, more pronounced peak of molt activity in October. By contrast, males in older predefinitive-plumage stages and males in definitive plumage exhibited comparable unimodal distributions in molt activity beginning in June and peaking between July and October. Our data are consistent with selective pressure to avoid the costs of molt-breeding overlap in females and older males. Our findings have important implications for social organization and signaling in Long- tailed Manakins, and for the evolution of delayed plumage maturation in birds.Desarrollo del Plumaje y Muda en Chiroxiphia linearis: Variación de Acuerdo al Sexo y la Edad

PLUMAGE DEVELOPMENT AND MOLT IN LONG-TAILED MANAKINS (CHIROXIPHIA LINEARIS): VARIATION ACCORDING TO SEX AND AGE

Lek-mating Long-tailed Manakins (Chiroxiphia linearis) exhibit an unusual pattern of delayed plumage maturation. Each year, males progress through a series of predefinitive plumages before attaining definitive plumage in their fifth calendar year. Females also exhibit variation in plumage coloration, with some females displaying male-like plumage characteristics. Using data from mist-net captures in northwest Costa Rica (n = 1,315) and museum specimens from throughout the range of Long-tailed Manakins (n = 585), we documented the plumage sequence progression of males, explored variation in female plumage, and described the timing of molt in this species. Males progressed through a series of age-specific predefinitive plumages, which enabled the accurate aging of predefinitive-plumaged males in the field; this predefinitive plumage sequence is the basis for age-related status-signaling in these males. Females tended to acquire red coloration in the crown as they aged. However, colorful plumage in females may be a byproduct of selection on bright male plumage. Females exhibited an early peak of molt activity from February to April, little molt from May through July, and a second, more pronounced peak of molt activity in October. By contrast, males in older predefinitive-plumage stages and males in definitive plumage exhibited comparable unimodal distributions in molt activity beginning in June and peaking between July and October. Our data are consistent with selective pressure to avoid the costs of molt-breeding overlap in females and older males. Our findings have important implications for social organization and signaling in Long- tailed Manakins, and for the evolution of delayed plumage maturation in birds. Desarrollo del Plumaje y Muda en Chiroxiphia linearis: Variación de Acuerdo al Sexo y la Edad

Sexual dichromatism in North Island Robins (Petroica longipes) is weakened by delayed plumage maturation in males and females

The North Island Robin (Petroica longipes) is an endemic New Zealand passerine with melanin-based plumage of grey-brown and black, with males typically described as having darker plumage than females. In this study we quantified the relationship of sex and age on plumage colour in 32 North Island Robins on Tiritiri Matangi Island, New Zealand. We objectively scored plumage colour in each individual relative to a colour identity chart created with reference to HTML code. Our results support the general assertion that males are darker than females in this species. However, we found that this is significantly confounded by the age of the bird in both sexes and that this relationship is not a simple dichotomy between first-year breeders and adults. This is the first study to document the existence of delayed plumage maturation in the female of this species, and that plumage changes occur over many years in both sexes. The plumage of most Robins lies within the colour-range overlap between the sexes, indicating that plumage colour is not a reliable criterion for sexing this species. We used a classification and regression tree (CART) analysis to determine which morphometric measures were the best classifiers of gender in birds within the colour-range overlap; a tarsus measure cut-off of ~36 mm accurately predicted gender in >80% of cases. We propose that delayed plumage maturation in this species results from social and physiological factors during moult, which affect melanin production and the colouring of the feathers.

Delayed plumage maturation in socially isolated juvenile zebra finches, Taeniopygia guttata

We investigated the effect of social variables on the regulation of the moult from juvenile to adult plumage in male zebra finches. Males reared in social isolation after day 31 after hatching retained their juvenile plumage until day 90; if then placed in a colony setting, they developed the typical male plumage in 2–3 weeks. The isolation-induced delay in male plumage resulted from a delay in the juvenile moult. Social isolates that could trigger song playbacks by pecking at a key developed male plumage at the same time as controls. We suggest that a nongonadal mechanism sensitive to social variables normally ensures that adult male plumage is acquired in zebra finches during the weeks leading up to sexual maturity. This is the first report of a social effect on moult.

Plumage color as a status signal in male–male interaction in the red-flanked bushrobin, Tarsiger cyanurus

Recent studies have suggested that structural-based coloration is an honest signal of male genetic and/or conditional quality in sexual selection. However, whether structural coloration functions in intrasexual competition is unknown. We examined whether plumage color functions as a status signal during intrasexual interactions in the red-flanked bushrobin Tarsiger cyanurus; adult males have many blue plumes as structural coloration whereas yearling males and females are olive brown with few blue plumages. Blue males did not always dominate olive-brown males. The number of interactions did not differ with the colors of the two birds involved. The interactions of a blue male and an olive-brown male were less aggressive than those of two blue or of two olive-brown males. In this study, we found that structural plumage coloration may serve as a signal of aggressive intent and lower the escalation level of an aggressive interaction in a manner consistent with hypotheses regarding the evolution of delayed plumage maturation.

‘Elepaio subadult plumages reduce aggression through graded status-signaling, not mimicry

The 'Elepaio (Chasiempis sandwichensis) is a monarch flycatcher endemic to the Hawaiian Islands. Both sexes have a two-year delay in plumage maturation, with distinct first-year and second-year subadult plumages. This study tested hypotheses for the evolution of delayed plumage maturation in 'Elepaio by presenting adult males with models representing different ages and sexes in the breeding and nonbreeding seasons. The subadult plumages of 'Elepaio appeared to serve as honest, graded signals of status that reduced aggression from dominant adults. Both first-year and second-year subadult male models were attacked less than adult male models, and aggression increased linearly with age of male models. Neither subadult plumage appeared to function in sexual mimicry or juvenile mimicry. Second-year male models were attacked more than adult female models; neither subadult plumage resembles adult plumage of the opposite sex. First-year male models, which are juvenile-like, were not attacked more than adult female models, but juvenile mimicry cannot account for the behavior toward second-year male models and is a less parsimonious explanation. Aggression toward models was much higher in the breeding season, and all models were treated similarly in the nonbreeding season, suggesting competition for mates has been the primary selective force shaping the evolution of the 'Elepaio's plumage coloration. Models made from color pho- tocopies can be a useful alternative to museum specimens in behavioral studies of rare species or those in which damage to specimens during model presentation would occur.

Ontogeny of male plumage dichromatism in Madagascar paradise flycatchers Terpsiphone mutata

Two male plumage morphs, ‘white’ and ‘rufous’, coexist in the Madagascar paradise flycatcher Terpsiphone mutata. There has been enduring debate about whether this dimorphism in male plumage represents seasonal dichromatism, delayed plumage maturation, or genetic differences. We present data from a nine‐year study monitoring plumage changes in 119 individually colour‐banded males (430 male‐years). Our data show that paradise flycatchers are not seasonally dichromatic, and that although males show delayed plumage maturation, the rufous morph is not simply a precursor to white plumage, as previously thought. Individual males followed irreversible developmental pathways to ‘rufous’ or ‘white’, and could be reliably assigned to these distinct phenotypes by their second year. ‘White’ males adopted definitive plumage by the age of three years, whereas ‘rufous’ males did so between the ages of three and six years. The fixed nature of these morphs suggests that a genetic basis for the dichromatism is likely. However, variation in the timing of definitive plumage acquisition in rufous males could involve condition dependence and be environmentally influenced.

Winter Age Ratios and the Assessment of Recruitment of Harlequin Ducks

-Recruitment is the process by which young birds are added to the breeding population. The two most commonly used methods to estimate recruitment in ducks are pair/brood counts, and fall age ratios based on wings returned by hunters. Direct counts on the wintering area to determine the proportion of young males to adult males (age ratios), can be used for species with delayed plumage maturation. This is useful for species that are difficult to study on the breeding grounds and are seldom hunted, such as Harlequin Ducks (Histrionicus histrionicus). Such an approach is only valid if age classes are equally sampled. Between 1994 and 1999, the proportion of male Harlequin Ducks that were immatures in the Strait of Georgia, British Columbia, was estimated at 0.068. The proportions differed across years. Little difference occurred through the winter months until spring, when there was a significant increase in proportions in March. If these age ratios are accurate, then recruitment would not be compensating for annual adult mortality and the population could have been declining during the period of our study. However, if immature males are not distributed evenly among the population, then our assessment may underestimate or overestimate proportions. Delayed breeding means that immature birds experience several additional seasons of mortality prior to breeding, and thus the actual recruitment rate into the breeding population would be lower than that presented here. Received 11 April 2000, accepted 18July 2000.

Age‐related reproductive success in dichromatic male Black Redstarts Phoenicurus ochruros: Why are yearlings handicapped?

Reproductive constraints on sexually mature, young birds may be the underlying cause for the evolution and maintenance of delayed plumage maturation in passerine birds. I examined whether yearling male Black Redstarts in non‐definitive plumage are reproductively handicapped and explored possible reasons for it. Yearlings raised only half as many young per season as adults. Differential reproductive effort was excluded as a possible source for age‐related reproductive success because yearlings and adults did not differ in the frequency of non‐breeding or in paternal effort. The lower annual reproductive success of yearlings was attributed to their lower probability of obtaining (multiple) females and adult females. Males mated to adult females raised almost twice as many offspring as males mated to yearling females. I conclude that the proposed preconditions for the evolution and maintenance of delayed plumage maturation do still prevail in the Black Redstart.

Costs and Benefits of Subadult Plumage in Mute Swans: Testing Hypotheses for the Evolution of Delayed Plumage Maturation.

In some avian species, young birds capable of reproducing diminish their prospects of doing so by molting into a subadult plumage that accurately signals their subadult status. Several hypotheses have been proposed to explain the evolution of delayed plumage maturation, but testing them usually has involved interspecific comparisons that are hard to interpret. Mute swans (Cygnus olor) exhibit two phenotypes that differ in whether the birds have a gray subadult plumage (SAP phenotype) or molt immediately into an all white adult plumage (AP phenotype). The AP phenotype results from a recessive allele on the X chromosome; both phenotypes occur in the same population and even in the same brood. We compared costs and benefits of both phenotypes in mute swans on the Chesapeake Bay in 1972-1980 and on Long Island Sound in 1982-1989. Swans with the SAP phenotype had higher survival rates from hatching to fledging than AP swans. In the fall, when AP cygnets began to molt into their white plumage, their parents often attacked and drove them off while allowing SAP cygnets from the same brood to remain on their territories for several more months. SAP males had higher survival rates during their first 2 yr of life than AP males, but AP swans bred at a younger age than SAP swans. The only proposed hypothesis for the evolution of delayed plumage maturation that can explain its occurrence in mute swans is the status-signaling hypothesis. This hypothesis argues that males with subadult plumage honestly advertise their age and subordinate status while AP swans are cheaters and engaging in dishonest communication. SAP males acquire a longer period of parental care, suffer less aggression from older birds, and increase their survival but forgo the opportunity to breed at an early age. This is a unique example of how a single gene resulted in either honest or dishonest communication, changed a bird's relationship with its parents and potential mates, and altered the bird's chances to survive and to reproduce.

Delayed maturation in passerine birds: an examination of plumage effects and some indications of a related effect in song

In some passerine species, 1st-year males are clearly distinguishable from adults; they have a different, typically dull, plumage. At least 15 explanations of the delayed plumage maturation of 1st-year males have been proposed. In the present study, we investigate if there is a similar widespread phenomenon regarding song, i.e. if males of some species have a distinct song in their first breeding season (delayed song maturation). A comparative analysis of 137 West Palearctic passerines showed that detailed data on how the song changes with age in breeding males is available for only a few species. Moreover, it is difficult to assess whether the song features continue to change considerably year after year or if, as we suggest, the main difference is between 1st-year vs 2-years and older males. We found that species with a suggested delay in song maturation were mostly those with delayed plumage maturation; a preliminary comparison suggests that these species have greater longevity. We also discuss the evolutionary significance of delayed song and plumage maturation and we suggest some possible directions for future research on these phenomenona.

Reproductive Consequences of Autumnal Singing in Black Redstarts (Phoenicurus Ochruros)

AbstractIn a migratory population of Black Redstarts (Phoenicurus ochruros) in central Europe, males were territorial and sang in autumn between the end of molt in early September and the abandonment of territories in October. Participants in autumn singing were adult males past their first potential breeding season; subadults rarely defended territories in autumn. Prior to the autumn singing period, unmated males and males after their first breeding season often dispersed to new locations within the study site. Pair associations with experienced female breeders still present on the breeding ground were preformed. Low winter mortality, site dominance, and fidelity to autumn territories allowed the reformation of 59% of autumnal pair bonds in the following spring. The mating pattern was assortative by age because the initiation of territory acquisition and pair formation was temporally segregated by more than six months between subadult and adult breeders. Males benefitted from mating with experienced females because they started breeding earlier and initiated more breeding attempts per season. Autumnal singing and territoriality, a phenomenon that has not attracted much attention, may play a key role in the understanding of age-related reproductive asymmetries in Black Redstarts. Age-related reproductive performance may be the underlying cause for the evolution of delayed plumage maturation in this species.

REPRODUCTIVE CONSEQUENCES OF AUTUMNAL SINGING IN BLACK REDSTARTS (PHOENICURUS OCHRUROS)

In a migratory population of Black Redstarts (Phoenicurus ochruros) in central Europe, males were territorial and sang in autumn between the end of molt in early September and the abandonment of territories in October. Participants in autumn singing were adult males past their first potential breeding season; subadults rarely defended territories in autumn. Prior to the autumn singing period, unmated males and males after their first breeding season often dispersed to new locations within the study site. Pair associations with experienced female breeders still present on the breeding ground were preformed. Low winter mortality, site dominance, and fidelity to autumn territories allowed the reformation of 59% of autumnal pair bonds in the following spring. The mating pattern was assortative by age because the initiation of territory acquisition and pair formation was temporally segregated by more than six months between subadult and adult breeders. Males benefitted from mating with experienced females because they started breeding earlier and initiated more breeding attempts per season. Autumnal singing and territoriality, a phenomenon that has not attracted much attention, may play a key role in the understanding of age-related reproductive asymmetries in Black Redstarts. Age-related reproductive performance may be the underlying cause for the evolution of delayed plumage maturation in this species.

Costs and Benefits of Subadult Plumage in Mute Swans: Testing Hypotheses for the Evolution of Delayed Plumage Maturation

Costs and Benefits of Subadult Plumage in Mute Swans: Testing Hypotheses for the Evolution of Delayed Plumage Maturation

Age structure and density of red-capped robin populations vary with habitat size and shape

Summary 1. In order to determine the influence of habitat shape on aspects of the population dynamics of birds, 196 male red-capped robins Petroica goodenovii were surveyed using song playback in large non-linear woodland remnants and linear roadside remnants in the wheatbelt of south-eastern Australia. 2. The average density of male robins was significantly higher in large non-linear remnants [0·86 ± 0·09 (SD) birds ha–1] than in small linear remnants [0·35 ± 0·16 (SD) birds ha–1]. 3. Red-capped robins exhibit delayed plumage maturation, and 14% of the males captured were yearlings. This percentage was significantly higher in roadside remnants (20%) than in large, non-linear remnants (8%). 4. These results indicate that different population processes are occurring in the individual remnants and the dynamics of the metapopulation are potentially complex. 5. Land managers must not focus excessively on wildlife corridors (narrow, linear habitats) at the expense of appropriate management and restoration of large areas of native vegetation.

Plumage brightness in relation to haematozoan infections in the greenfinch Carduelis chloris: Bright males are a good bet

Variation in plumage brightness (yellowness) and prevalence and intensity of haematozoan infections in greenfinches Carduelis chloris L. were studied in three populations, widely separated in geographic location from Spain to Finland. Sexual dichromatism (SD) in coloration was marked, males being yellower than females. Although older birds were generally yellower than younger birds, the degree of SD in coloration increased with age, perhaps due to delayed plumage maturation in males. The prevalence of haematozoan infections was unrelated to any measure of male plumage coloration, but the intensity of haematozoan infections was strongly negatively related to male plumage brightness, and this pattern was similar in all three populations. Hence, male plumage brightness reveals information about the extent to which males are parasitized. This result is in accordance with the Hamilton-Zuk hypothesis, which suggests that bright male plumage has evolved to indicate heritable resistance to parasites. The fact that lightly-infected males had brighter plumage than non-infected and heavily infected ones may suggest that non-infected males were a mixture of both susceptible and resistant individuals, whereas lightly infected individuals might have been effectively immune to parasites. Our data provide a clear example of the negative association between plumage brightness and blood parasite loads in birds, and suggest that male plumage yellowness in the greenfinch can function as an indicator of male quality.