Sex differences in body size and body condition in breeding Temminck’s Stints Calidris temminckii

There have been very few reports of body size measurements of live Temminck’s Stints, but earlier studies have shown sex differences in body mass and tarsus length. Here we use molecular techniques to determine the sex of Temminck’s Stints from a Norwegian breeding population. In total, we report measurements of body weight, wing length, tarsus length, bill length, skull length and keel length from 17 males and 30 females. We found significant sex differences in all of these variables, with the exception of tarsus length. The differences in skull length disappeared after the bill lengths had been subtracted from the measurements. A discriminant function analysis based on wing length and bill length correctly classified 86% of the cases (12/16 males, 25/27 females). Female Temminck’s Stints are known to regularly lay more than one clutch of eggs per season and could therefore be expected to be physiologically deprived of bodily energy stores. Nevertheless, we found females to be in better body condition than males.     

Sexing greater flamingos by weight and linear measurements

The sex of 59 adult Greater Flamingos (Phoenicopterus ruber roseus L.) was determined by laparoscopic exam of the gonads. Concomitant body weight (kg) and linear measurements (mm) of the culmen (bill), tarsus, middle toe, and wing were taken and compared for males vs. females. Although an overlap between sexes existed in all measurements, males on average were larger than females. Student's t-test indicated significant sexual differences for all five measurements. Thus, weights and linear measurements—especially tarsus, middle toe, and wing length—appear to be a useful parameter in determining an individual's sex in lieu of laparoscopic, feather pulp, blood chromosome, or fecal steroid analysis.     

The adaptive significance of electrophoretic mobility in phosphoglucose isomerase (PGI)

Sexual dimorphism in size and plumage was investigated in the lek-breeding Jackson's widowbird Euplectes jacksoni. Size dimorphism was evident from the sexual difference in tarsus length, reflecting skeletal body size. The long tail and the wide collar of breeding plumaged males were obvious secondary sex traits, but the wing was also longer than in subadults and might likewise be sexually selected (i.e. not merely a byproduct of body size). Possibly, the increased wingspan functions to save energy during the jump display. To reveal intrasexual selection, courtholders were compared with floaters (nuptial males captured off the leks), and were found to be larger in body size, wing length, collar and tail. The roles of inter-and intrasexual selection are discussed with reference to previously demonstrated female choice, and new results indicating competition for access to leks: quick reoccupation of deserted display courts, frequent observations of intruders and a finding that central males were more aggressive than peripherals. Observations imply that the collar is an agonistic signal that is neutral with respect to female choice. Possible contributions of natural selection to the sexual dimorphism are also considered.     

Quantitative genetics of ontogeny of sexual dimorphism in red junglefowl (Gallus gallus)

We studied phenotypic patterns and underlying quantitative genetics of development of sexual size dimorphism in red junglefowl (Gallus gallus). Using a multigenerational pedigree and the 'animal model' technique, we found significant heritability for many of the size and growth-related traits we examined, as well as significant genetic correlations among them. Despite sexual size dimorphism throughout posthatching ontogeny, the genetic correlation between males and females for all size measurements and growth parameters remained high. Significant positive phenotypic and genetic correlations between the fastest rate of growth and mass at week 26 (near asymptote) indicate that faster growth when young promotes larger adult size. However, age at which peak growth is reached does not appear to be phenotypically or genetically correlated with adult size. Positive genetic correlations within traits among ages were common, demonstrating that the genetic variance important to growth is relatively consistent among ages. However, male mass and tarsus length showed no genetic correlation between week 0 values and those from later ages. The body size traits of mass and tarsus length were genetically correlated with each other in females, but this pattern was not significant in males. Thus, despite striking sexual dimorphism in size and growth trajectories, size dimorphic traits in junglefowl show, with some exceptions, genetic integration between the sexes, among ages, and between traits.     

大山雀身体大小的性二态及其季节变化

动物中普遍存在雌雄个体身体大小的性二态现象。了解近缘种之间身体大小性二态现象的差异，可为深入探讨身体大小性二态现象的潜在驱动机制提供证据。国外对欧亚大山雀（Parus major）的研究发现，其喙长、跗跖长、翅长等 6 项身体大小指标存在着明显的性二态，且喙长的性二态存在季节间差异。大山雀（P. cinereus）曾被作为欧亚大山雀的一个亚种，其形态和行为与欧亚大山雀存在着诸多相似之处。为探讨大山雀是否也存在身体大小性二态及季节性差异，本研究分析了 2018 至 2020 年间在河南董寨国家级自然保护区捕捉的 226 只（雌性 96 只和雄性 130 只）大山雀的喙长、头喙长、跗跖长、翅长、尾长和体长这 6 项体征指标的两性差异及其季节变化。结果显示，大山雀上述 6 项身体大小指标均存在不同程度的性二态现象，且雄性个体仅喙长与雌性的差异不显著，其余 5 项指标均显著大于雌性。此外，身体大小指标的两性差异不随季节显著变化，但两性的跗跖长在秋季均显著短于冬季和繁殖季，尾长在繁殖季均显著长于秋季和冬季。上述结果表明，大山雀身体大小的性二态及其季节性差异与欧亚大山雀并不完全相似。无论其身体大小存在性二态和季节变化的原因，还是其与欧亚大山雀在身体大小性二态模式上的差别，都有待今后进一步的研究。     

Growth and development of the European ferret (Mustela putorius)

Body weight, body length, and other developmental parameters were studied in the European ferret, Mustela putorius, from birth to 26 weeks of age. Males and females did not differ in weight until the seventh week of live, and they did not differ in length until the ninth week of life, when the males began to grow faster. Adult males (1400--1500 g) were heavier than adult females (800--900 g), but females reached adult size faster than males.     

Influence of different photoperiods on development of gonad, cloacal gland and circulating thyroid hormones in male Japanese quail Coturnix coturnix japonica.

One day old chicks of Japanese quail were exposed to different photoperiods (LD, 8:16, 13.5:10.5, 16:8 and LL) and observations (testes weight, cloacal gland size, body weight and circulating thyroxine and triiodothyronine) were taken at the age of 3, 5, 7, 9 and 16 weeks. Results indicate that immediate reproductive development occurred in birds exposed to long photoperiods (greater than 12 hr). Growth under LD 8:16, was not apparent till 7th week and by 16 weeks, degree of gonadal development was similar in all the birds, irrespective of photoperiodic treatment. Whereas body weight of the intermediate and long day (LD 13.5:10.5, 16:8 and LL) treated birds increased upto 5th week and remained constant thereafter. But the chicks maintained under short day length (LD 8:16), showed spontaneous increase till the end of the study and birds were much heavier compared to all other groups. Plasma T4 concentration increased with increasing age till 9th week and remained unaltered thereafter. On the other hand T3 level did not change till 7th week followed by a decline. It is suggested that the initiation and degree of gonadal growth in quail depends on the availability of daily photoperiod, until the achievement of full breeding condition. Peak level of T4 observed in 9 week old birds may be involved in the development of photorefractoriness at that age.     

Subtle but ubiquitous selection on body size in a natural population of collared flycatchers over 33 years

Understanding the magnitude and long‐term patterns of selection in natural populations is of importance, for example, when analysing the evolutionary impact of climate change. We estimated univariate and multivariate directional, quadratic and correlational selection on four morphological traits (adult wing, tarsus and tail length, body mass) over a time period of 33 years (≈ 19 000 observations) in a nest‐box breeding population of collared flycatchers (Ficedula albicollis). In general, selection was weak in both males and females over the years regardless of fitness measure (fledged young, recruits and survival) with only few cases with statistically significant selection. When data were analysed in a multivariate context and as time series, a number of patterns emerged; there was a consistent, but weak, selection for longer wings in both sexes, selection was stronger on females when the number of fledged young was used as a fitness measure, there were no indications of sexually antagonistic selection, and we found a negative correlation between selection on tarsus and wing length in both sexes but using different fitness measures. Uni‐ and multivariate selection gradients were correlated only for wing length and mass. Multivariate selection gradient vectors were longer than corresponding vector of univariate gradients and had more constrained direction. Correlational selection had little importance. Overall, the fitness surface was more or less flat with few cases of significant curvature, indicating that the adaptive peak with regard to body size in this species is broader than the phenotypic distribution, which has resulted in weak estimates of selection.     

Multiple ornaments are positively related to male survival in the common pheasant

Several empirical studies have reported a positive relation between male viability and the expression of sexually selected traits, but others have reported a significant negative relation. Using the ability to evade predators as an indicator of male viability, we evaluated the direction of this relationship in a free-ranging population of common pheasants,Phasianus colchicus , which have multiple ornaments and are sexually dimorphic in tail length and in ornaments such as wattles and tarsal spurs. We translocated 72 males into a protected area and radiotracked them during the breeding seasons of 3 years. Before releasing them, we measured their body weight, wing and tail length, wattle height and spur length. Male survivors had larger multiple ornaments, regardless of age, than males that were killed by predators but survival selection on wing length and body weight was nonsignificant, showing that selection on male ornaments was not the result of selection on correlated traits.Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

Gender determination by body weight and linear measurements in American and Chilean flamingos,previously surgically sexed: Within-sex comparison to greater flamingo measurements

Gender was determined by laparoscopic visualization of the gonads for 38 adult American flamingos (Phoenicopterus ruber ruber L.) and 36 adult Chilean flamingos (P. chilensis L.). Concomitant body weight (kg) and linear measurements (mm) of the culmen (bill), tarsus (tarsometatarsus), middle toe, and wing were taken. Statistical comparisons of body weight and linear measurements for male vs. female were made for each species. Also, the same-sex statistical comparisons were made between these two species, and between each of these two species and with data for greater flamingos (P. r. roseas L.) from a previous publication. As previously published for greater flamingos, an overlap between sexes existed in all measurements with males on average larger than females for both American and Chilean flamingos. However, Students' t-test indicated a significant sexual difference for all measurements between males and females of each species except for culmen length in Chilean flamingos. Students' t-test also indicated a significant difference when species were compared (Chilean vs. greater, and American vs. Chilean) and subspecies (American vs. greater) were compared for most of the 5 measurements. Thus, despite limitations imposed by between-sex overlap, weights and linear measurements, especially tarsus, middle toe, and wing length, appear to be useful in determining an individual's gender when species or subspecies identification is considered.     

Sexual size dimorphism and assortative mating for morphological traits in Passer domesticus

In this study, assortative mating for different morphological traits was studied in a captive population of house sparrows (Passer domesticus). Males were larger than females. Assortative mating was found for tail length, wing length and general body size. Males with larger badge size mated with females with longer tails. The strongest assortative mating occurred for tail length (r=0.77), and this assortative mating remained significant after controlling for wing length, mass and tarsus length, suggesting that it was not an artefact of assortative mating for body size. The possibility of sexual selection for tail length in the house sparrow is discussed.     

SEXUAL SELECTION IN THE BARN SWALLOW (HIRUNDO RUSTICA). IV. PATTERNS OF FLUCTUATING ASYMMETRY AND SELECTION AGAINST ASYMMETRY

The patterns of variation in fluctuating asymmetry were studied in four morphological characters of the barn swallow Hirundo rustica. The level of absolute and relative asymmetry was larger in the secondary sexual character “outer tail length” than in three nonsexual morphological traits (wing, central tail, and tarsus length). The extent of individual asymmetry in outer tail length was negatively correlated with tail-ornament size, whereas the relationship between asymmetry of all other morphological characters and their size was flat or U-shaped. Asymmetry in outer tail length was unrelated to asymmetry in other morphological characters, whereas asymmetries in the length of wing, central tail, and tarsus were positively correlated. Male bam swallows exhibited larger asymmetry in outer tail length than females. Asymmetry of most morphological traits exhibited intermediate repeatabilities between years, with the exception of male and female outer tail length, which were highly repeatable. Tail asymmetry of offspring weakly, though significantly, resembled that of their parents. Asymmetry in wing and outer tail length was also significantly related to several fitness components. Male barn swallows that acquired a mate were less asymmetric in wing and outer tail length than unmated males. Females with more asymmetrical tails laid eggs significantly later. Annual reproductive success was unrelated to fluctuating asymmetry. Male barn swallows that survived were less asymmetric in wing and outer tail length than nonsurvivors, whereas female survivors were less asymmetric in outer tail length than nonsurvivors. These results suggest that levels of fluctuating asymmetry in barn swallows are associated with differences in fitness.     

Sexual size dimorphism and positive assortative mating in red-backed shrike Lanius collurio: an adaptive value?

During field studies in 1997–1999 in South Bohemia (Czech Republic), we found significant differences in size between the sexes in a local breeding population of red-backed shrike Lanius collurio. Males were significantly larger than females for wing length and tarsus length, but had smaller body mass than females. However, there was considerable overlap in the ranges of these parameters between the sexes. Interestingly, pairs were formed at random with respect to wing length and tarsus length, but assortative mating was significant for body mass/body condition. Among tested variables, only male wing length correlated significantly with nestling body mass at day 7. However, clutch size and the number of fledglings strongly depended on differences in tarsus length between mates, but not on body size of mates. Individual improvements in foraging skills and/or courtship feeding rates are proposed as possible explanations for these findings.     

Sexual variation in heritability and genetic correlations of morphological traits in house sparrow (Passer domesticus)

Estimates of genetic components are important for our understanding of how individual characteristics are transferred between generations. We show that the level of heritability varies between 0.12 and 0.68 in six morphological traits in house sparrows (Passer domesticus L.) in northern Norway. Positive and negative genetic correlations were present among traits, suggesting evolutionary constraints on the evolution of some of these characters. A sexual difference in the amount of heritable genetic variation was found in tarsus length, wing length, bill depth and body condition index, with generally higher heritability in females. In addition, the structure of the genetic variance-covariance matrix for the traits differed between the sexes. Genetic correlations between males and females for the morphological traits were however large and not significantly different from one, indicating that sex-specific responses to selection will be influenced by intersexual differences in selection differentials. Despite this, some traits had heritability above 0.1 in females, even after conditioning on the additive genetic covariance between sexes and the additive genetic variances in males. Moreover, a meta-analysis indicated that higher heritability in females than in males may be common in birds. Thus, this indicates sexual differences in the genetic architecture of birds. Consequently, as in house sparrows, the evolutionary responses to selection will often be larger in females than males. Hence, our results suggest that sex-specific additive genetic variances and covariances, although ignored in most studies, should be included when making predictions of evolutionary changes from standard quantitative genetic models.     

Sex-specific growth patterns and effects of hatching condition on growth in the reversed sexually size-dimorphic great skua Stercorarius skua

In many sexually size-dimorphic species of birds and mammals, the larger sex, often the males, show increased environmental sensitivity during ontogeny. This is generally assumed to be due to higher energy requirements, reflected in higher absolute growth rates of the larger sex. Poor early conditions often increase the sex differences in vulnerability. However, it is not clear whether these patterns are equally pervasive in species where females are larger, as males face an additional early disadvantage due to high levels of testosterone. We investigated sex-specific growth patterns of mass, tarsus and wing of the great skua Stercorarius skua , a seabird with reversed size dimorphism. We were particularly interested in sex-specific effects of early conditions on growth. Beside data from unmanipulated nests, we present results from an egg removal experiment, which caused chicks to hatch from smaller eggs and in poorer body condition. Half of the experimental chicks were raised by pairs in which mothers were in poor body condition. At the end of the nesting period, great skua chicks exhibited a comparable degree of size dimorphism as is found in adults, although neither sex had reached final adult size. Despite females reaching larger asymptotic values of mass and tarsus, timing of growth was not different between the sexes. Absolute growth was higher for females around the time of maximum growth, which suggests that daughters face higher energetic demands. We found sex-specific effects of poor early conditions on growth patterns, although not to the extent which we had predicted. Hatching in poor body condition was related to slowed growth in females but not males. However, our experimental manipulations had no additional negative effect on growth. Our results indicate that daughters in the great skua face higher demands during growth than sons, and that early conditions are more important for the development of the larger sex in this reversed dimorphic species.     

The evolution of sexual size dimorphism in the house finch. III. Developmental basis

Sexual size dimorphism of adults proximately results from a combination of sexually dimorphic growth patterns and selection on growing individuals. Yet, most studies of the evolution of dimorphism have focused on correlates of only adult morphologies. Here we examined the ontogeny of sexual size dimorphism in an isolated population of the house finch (Carpodacus mexicanus). Sexes differed in growth rates and growth duration; in most traits, females grew faster than males, but males grew for a longer period. Sexual dimorphism in bill traits (bill length, width, depth) and in body traits (wing, tarsus, and tail length; mass) developed during different periods of ontogeny. Growth of bill traits was most different between sexes during the juvenile period (after leaving the nest), whereas growth of body traits was most sexually dimorphic during the first few days after hatching. Postgrowth selection on juveniles strongly influenced sexual dimorphism in all traits; in some traits, this selection canceled or reversed dimorphism patterns produced by growth differences between sexes. The net result was that adult sexual dimorphism, to a large degree, was an outcome of selection for survival during juvenile stages. We suggest that previously documented fast and extensive divergence of house finch populations in sexual size dimorphism may be partially produced by distinct environmental conditions during growth in these populations.     

Early nutrition causes persistent effects on pheasant morphology

Differences in growth conditions during early ontogeny have been suggested to cause permanent effects on the morphology and quality of birds. Yearly variation in growth conditions could thus result in morphological and quality differences between cohorts. In this study, we investigated the effect of small differences in the dietary protein content of captive ring-necked pheasants (Phasianus colchicus) during their first 8 wk posthatching. An experimental increase of the proportion of dietary protein during the first 3 wk of life accelerated growth, whereas a similar manipulation during the following 5 wk had only a limited effect. Compensatory growth during the postexperimental period equalized the size of chicks from different experimental treatments. However, a difference in tarsus length resulting from experimental treatment during the first 3 wk remained into adulthood. Furthermore, the protein content of the diet during the first 3 wk had an effect on the degree of fluctuating asymmetry in tarsus length, suggesting persistent effects on the quality of birds. The results of this study may explain size differences between cohorts that exist in pheasants and may also provide a link between the use of pesticides in agriculture and population effects on pheasants.     

Sex-specific differences in compensation for poor neonatal nutrition in the zebra finch Taeniopygia guttata

Individuals can compensate for poor early nutrition by accelerating their growth rates once diet improves, but if malnutrition occurs at a key stage of development only certain body structures may compensate fully. This degrees of compensation is predicted to differ between the sexes and also between species with different life history strategies. In this paper we determine how males and females in a short-lived bird species, with only slight size dimorphism, differ in their abilities to compensate for a poor start in life. Here, zebra finch Taeniopygia guttata chicks from 93 broods were reared on either a standard quality (SQ), or low quality (LQ) diet for the first 15 d of life, followed by a standard diet for the rest of their lives. Thus, the period of nutritional manipulation was relatively short compared with previous studies. Nestlings on a LQ diet showed slower body mass and tarsus growth rates than those on SQ diet but this was reversed after the diet of the LQ birds was improved. LQ birds of both sexes were able to fully compensate in terms of body mass and beak colour, but not tarsus length. Body size and beak colour are sexually selected traits in male zebra finches. By adulthood LQ females had significantly shorter wings than other birds, apparently directing resources into sex-specific structures instead of feather and skeletal growth. Thus, our experiment showed that the sexes differed in how they phenotypically compensated for a poor start in life. Males in particular invested sparse resources into structures associated with mate acquisition, as proposed by life history theory for a species that 'lives fast and dies young.' We predict that this relatively short period of malnutrition during early development will have long term, sex-specific, fitness consequences for these birds.     

Sexual size dimorphism and sex identification using morphological traits of two Aegithalidae species

The black-throated tit, Aegithalos concinnus, and long-tailed tit, A. caudatus, are two widely-distributed species of Aegithalidae. They are thought to be monomorphic and thus difficult to differentiate between sexes in the field. We determined the sex of 296 black-throated tits and 129 long-tailed tits using DNA analysis, evaluated their sexual size dimorphism, and developed discriminant models to identify sex based on morphometries, including bill length, bill depth, bill-head length, maximum tarsus length, tarsus width, wing length, tail length, total body length, and body mass. Both species were sexually dimorphic in size, with males having larger measurements than females, except for bill length in black-throated tits, and both bill length and body mass in long-tailed tits. Moreover, both species showed similar sexual size dimorphism (SSD) among the morphological features, with tail length having the highest SSD value. The multivariate discriminant models for sex identification had an accuracy of 82% for both species, which was slightly higher than the best univariate discriminatory model for each species. Because of the complicated nature of the multivariate model, we recommend univariate models for sex identification using D = 0.491 × tail length - 24.498 (accuracy 80%) for black-throated tits and D = 0.807 × wing length - 45.934 (accuracy 78%) for long-tailed tits. Females in both species showed generally higher morphological variation than did males, resulting in lower accuracies in all discriminate functions regardless of univariate or multivariate approach. This could be the result of a sex-biased selective pressure in which males have higher selective pressures for these morphological features.     

Growth of nestling Barn Owls Tyto alba in central Mali

Data on growth of 276 young Barn Owls were analysed with respect to the effects of year and month of hatching, hatch order and brood order. Growth characteristics considered were weight; lengths of culmen, tarsus, central tail feathers and quill of third outermost primary; standard wing length; and wing span. For weight the growth constant K was 0151 and time t ₁₀- t ₉₀ was 32-2 days. Least-squares analyses showed that gain in weight and culmen and tarsus length were affected by month of hatching with young hatched in the middle part of the breeding season showing the most rapid growth. Hatch order affected gain in weight. Differences in growth rates of all these characters were not, however, reflected in differences in weight or length at fledging except for the effects of brood on weight with second broods fledging at significantly lighter weights than first ones. Predictive equations for character against age are provided for all linear measurements. All characters examined attained apparent asymptotes before fledging except tail and standard wing length.