Greenfinch plumage varies both between and within age and sex classes. This study looked at the possible causes and consequences of this variation in a colour-ringed population. Plumage colour was both repeatable and heritable. The function of colourful plumage in the breeding season was reviewed. Many aspects of the breeding biology of Greenfinches were studied and the effects of plumage on breeding success investigated. Brightly coloured birds seemed to have greater reproductive success than dull ones. Brightly coloured males were also more likely to ret urn to the study area in the following breeding season. Greenfinches are usually regarded as monogamous, but I found that over 25% of nests involved polygamy. Polygyny, polyandry and possible cases of polygynandry were recorded, but polygyny was the most common of the three. It was demonstrated that the experimental provision of food influenced the occurrence of polygyny. The literature generally considers polygyny to be bad for females, however in Greenfinches polygynous pairs were as successful at producing independent offspring as monogamous pairs. Polygynous birds recruited more offspring into the local population than monogamous birds, although this may reflect differences in dispersal. Since polygynous males were bright and had better survival and since colour was found to be heritable, females may have been choosing males for their good genes. If colour is an honest signal, there must be some cost preventing dull birds from becoming bright. Bright Greenfinches were more likely to be killed by Sparrowhawks during the summer than dull Greenfinches and they were also more likely to be injured. In comparison, dull birds were more likely to be killed by Tawny Owls in the winter. Whether Greenfinch plumage variation acted as a "badge of status" over the winter was investigated. The brighter a Greenfinch's plumage the more likely it was to win confrontations at a bird table in the winter, regardless of food type (contra Maynard Smith & Harper 1988). So what influenced a Greenfinch's plumage? Birds with damaged feathers only regrew bright plumage if they were in good body condition. Birds with low fat stores regrew paler feathers after damage, which is possibly related to the fact that the carotenoid pigment is stored in fat. Therefore, it is possible that after the breeding season good quality nales recovered faster, put on more fat and acquired brighter plumage in the moult. Plumage variation in the House Sparrow was also investigated. In hand estimates of bib size were correlated with spectrophotometric estimates of melanin content. Bib size was not related to organ size. The results of this study are compared with the literature on status signalling . It is argued that badges are handicaps i.e. uncheatable signals of individual quality, rather than being arbitrary signals or signalling Resource Holding Potential.

No description available.

Yellow avian plumage is a direct result of carotenoid pigments obtained in a bird’s diet and may act as an indicator for individual health, parasite resistance, and status. This study describes breast feather reflectance of adult Prothonotary Warblers (Protonotaria citrea) (n=169), insectivorous Neotropical migrant passerines, throughout the Ultraviolet (UV) and human visible light spectra and examines the relationship between Haemosporidia (pathogen causing Avian Malaria) infection and feather reflectance (n=41). Reflectance was characterized using a Principle Component Analysis evaluating Intensity, Brightness, Hue, UV Intensity, UV Brightness, and UV Chroma. UV and visible light reflectance was higher in birds sampled earlier in the field season (early clutch) (p=0.0017 and p=0.0743 respectively). There was no relationship between infection and either visible light or hue. However, UV reflectance was lower in infected birds (p=0.0843). This study suggests that UV reflectance is an important indicator for the infection status of a Neotropical migrant passerine.

Flamboyant plumage and ornamentation is common and well-known in male birds; it serves as a sexual display to attract potential mates. While flamboyant plumage is less common and usually more subtle in female birds, it does occur in some species such as Dark-Eyed Juncos (Junco hyemalis) and Prothonotary Warblers (Protonotaria citrea). Prothonotary Warblers display relatively subtle sexual dimorphism. This study examines variations in tail spot patterns in Prothonotary Warblers and relates those variations to age in females. Females with fewer than six spots tend to be two years old or younger; females with six spots or more tend to be three years old or older. The tail spot numbers of mated pairs were also analyzed. Statistical analyses indicate that males mate with females with six tail spots more often than they mate with females with other numbers of tail spots. This suggests males prefer females who are at least three years old.

Sexual selection can be defined as the difference in reproductive success among individuals that is related to their ability to acquire mates and fertilizations. Mathematical models have shown that combined with natural selection, sexual selection can be an important driver for speciation. There have also been a few case studies showing that sexual selection alone can lead to speciation in nature. Over the past 30 years, the barn swallow has become a classic model animal for sexual selection. The barn swallow has at least two sexually selected traits in different subspecies: the length of tail streamers in European barn swallows, H. r. rustica and ventral plumage colour in north American barn swallows, H. r. erythrogaster. Meanwhile molecular research on barn swallows shows that these barn swallow subspecies are recently derived and thus the barn swallow becomes an ideal model animal to test the theory that sexual selection drives speciation. The Barn Swallow species complex is comprised of six closely related subspecies distributed throughout the Holarctic. Whereas experimental studies in Europe, the Middle East and North America have been conducted, little is known about populations distributed across Asia. During my PhD study I collected barn swallow samples from more than 20 locations across China and compared the difference in morphology of Chinese barn swallow populations. The results show that in the northeastern part of China the barn swallow is intermediate in phenotype between subspecies in North America (H. r. erythrogaster) and subspecies in Europe (H. r. rustica), and is characterized by rusty ventral plumage colour and medium length tail streamers. Using morphological and colour traits, northeastern Chinese swallow populations can be separated from other Chinese populations, and this pattern of phenotypic variation may form under both natural and sexual selection. I also conducted an observational and experimental study on one of these populations, aiming to determine the extent to which variation in plumage color and tail streamers is underlain by sexual selection. The observational study reveals that for male barn swallows in my study population, clutch initiation date, the number of both social and genetic offspring and the body condition of nestlings can be predicted by the colouration of their ventral plumage, while the experiment shows that the reproductive success of male barn swallows tended to increase with experimental enhancement on their plumage colouration. My research supports that the ventral plumage colour is the sexually selected trait in northeastern Chinese barn swallows, and further experiments are needed to clarify the effect of male ventral plumage colour manipulation on their breeding success with the limitation of small sample size in my study.

While female mimicry and lower status signaling hypotheses of delayed plumage maturation have received much discussion in the literature, the experimental tests of these hypotheses have been infrequent. Those experimental tests often use a simulated intruder method with artificial model intruders rather than using live conspecific birds as intruders. Subadult male painted buntings (Passerina ciris) possess delayed plumage maturation where they appear visually identical to adult females during their first potential breeding season, while adult males are strikingly different in plumage coloration. Here I test the behavioral responses in a territorial population of painted buntings that exhibits extreme delayed plumage maturation using a simulated territorial intrusion experiment to measure territorial male behavioral response when presented with live caged intruders of both subadult and adult males. Territorial adult males were significantly more likely to initiate an attack and continue to attack caged adult male intruders than compared to caged subadult male intruders. This result supports both the female mimicry and status signaling hypotheses, and does not support the cryptic hypothesis. Additionally, in anecdotal observations, territorial males occasionally performed mating display behaviors to caged subadult male intruders. These results further suggest that territorial male painted buntings may identify subadult males as potential mates, supporting the female mimicry hypothesis for subadult males in this species. To what degree subadult males may benefit from DPM deserves further study.

Male birds of many species use conspicuous song and plumage displays in both courtship and territorial interactions. In some species, one or both of these signalling traits may not reach full adult maturity until a male’s second year of life. While the prevalence of delayed plumage maturation is well documented, delayed song maturation may be more difficult to detect. As a result, there are few studies which report age-based song differences between first-year and adult males. Additionally, despite the potentially large degree of variation of each trait within yearling males, little work has examined the benefits for young males who appear or sound more adult-like. Here, I investigate variation in both song and plumage displays of yearling male American redstarts (Setophaga ruticilla) as they relate to success during the breeding and non-breeding seasons. I first demonstrate a relationship between the degree of adult-like black plumage and both non-breeding season habitat quality in Jamaica and breeding season arrival date in Ontario. Previous studies have linked breeding season arrival date with winter habitat quality in adult males using stable-carbon isotope analysis. Together, these results suggest that variation in yearling male appearance may signal an individual’s competitive ability for high-quality resources. Next, I quantified the mate-attraction songs of both adult and yearling males and demonstrate a delayed maturation in this song type. I also present evidence of the potential benefits of expressing a more adult-like song by linking song structure with reproductive success in adult males. Finally, I demonstrate a potential relationship between the degree of adult-like song and plumage expression in yearling males, but not adult males. This work demonstrates that the delayed maturation of sexual signals may play an important role in the life-history of yearling male American redstarts, and highlights the need for in-depth analyses of individual variation of multiple sexual signals in this poorly-studied age class of birds. / Thesis (Master, Biology) -- Queen's University, 2009-09-25 10:42:19.794

The function of multiple display signals in golden whistlers (Pachycephala pectoralis) was investigated over three field seasons (2001/02 – 2003/04) at Toolangi State Forest (Victoria, Australia). Male golden whistlers are highly ornamented and possess several elaborate plumage displays, including a yellow breast and a conspicuous white throat patch. In addition, they are highly vociferous and possess large song repertoires. (For complete abstract open document)

Across avian systems, plumage ornamentation is often considered a signal of individual fitness, condition, sex, or status, and varies due to genetics or environmental sources. In species with structural coloration, plumage variation results from differences in the amount of energy allocated to feather growth during molt, presenting a unique opportunity to study the link between individual quality and ornamentation. In cooperative breeding species, such as the Florida Scrub-Jay (Aphelocoma coerulescens), the role of structural color as a signal is particularly important because helpers may delay breeding for one to several years and competition for space is high. Florida Scrub-Jay juveniles are sexually dimorphic in the ultraviolet range, and plumage color predicts social dominance and condition, but not adult reproductive fitness. Little is known about the consistency of ultraviolet reflectance across molts, and I tested the following questions: 1) does plumage color change across molts within individuals; 2) how do environmental variables and stress affect structural color; and 3) does adult color or change in color predict reproductive fitness? I measured relative change in color within individuals by comparing their juvenile and first set of adult feathers after pre-basic molt. I used several measures of nutritional condition, social dynamics, habitat quality, and parasite infection to model color, and I experimentally administered corticosterone during pre-basic molt to examine the effects of increased stress on color. Plumage reflectance was compared with breeding status to investigate the role of color in breeding space acquisition. Plumage reflectance was significantly different within individuals across molts, but juvenile and adult color were correlated. Adults were significantly less bright than juveniles, with higher proportions of UV chroma and hues shifted toward UV wavelengths. Variation in feather color was best explained by sex, mass, parasite infection, and an interaction between area of oak scrub and group size. Juvenile feather color was also strongly associated with mother ID, but this was not the case for adults even though adult color was correlated with juvenile color. Adult chroma was reduced in birds treated with corticosterone, and hues were shifted toward longer wavelengths. No measure of adult color predicted acquisition of breeding space, but change in brightness and hue were significant predictors of acquisition for females, where breeders tended to experience greater reductions in brightness and shifts toward UV hues compared to helpers. This may be due to sex-specific differences in reproductive strategies in Florida Scrub-Jays. Females tend to disperse farther distances and breed earlier than males, potentially expending more energy foraying and searching for breeding space, which could reduce brightness if it is linked with condition. These results suggest that sexual selection is not a dominant factor in plumage ornamentation for Florida Scrub-Jays, and understanding the interaction between plumage color, personality, and reproductive fitness should be a priority for future research.

Domestication is the process by which animals become adapted to the environment provided by humans. The process of domestication has let to a number of correlated behavioural, morphological and physiological changes among many domesticated animal species. An example is the changes of plumage colour in the chicken. Plumage colour is one of the most readily observable traits that make distinction between breeds as well as between strains within a breed. Understanding the genetic architecture of pigmentation traits or indeed any trait is always a great challenge in evolutionary biology. The main aim of this study was to map quantitative trait loci (QTLs) affecting the red and metallic green coloration in the chicken plumage. In this study, a total of 572 F8 intercross chickens between Red Junglefowl and White Leghorn were used. Phenotypic measurements were done using a combination of digital photography and photography manipulating software. Moreover, all birds were genotyped with 657 molecular markers, covering 30 autosomes. The total map distance covered was 11228 cM and the average interval distance was 17 cM. In this analysis, a total of six QTLs (4 for red and 2 for metallic green colour) were detected on four different chromosomes: 2, 3 11 and 14. For red colour, the most significant QTL was detected on chromosome 2 at 165 cM. An additional QTL was also detected on the same chromosome at 540 cM. Two more QTLs were detected on chromosomes 11 and 14 at 24 and 203 cM respectively. Additionally, two epistatic pairs of QTLs were also detected. The identified four QTLs together can explain approximately 36% of the phenotypic variance in this trait. In addition, for metallic green colour, one significant and one suggestive QTLs were detected on chromosomes 2 and 3 at 399 and 247 cM respectively. Moreover, significant epistatic interactions between these two QTLs were detected. Furthermore, these two QTLs together can explain approximately 24% of the phenotypic variance in this trait. These findings suggest that the expression of pigmentation in the chicken plumage is highly influenced by both the epistatic actions and pleiotropic effects of different QTLs located on different chromosomes.