Tarsus Length Research Articles

Breeding biology of the Xinjiang ground-jay Podoces biddulphi in the Taklimakan Desert, NW China

The Xinjiang ground-jay (Podoces biddulphi), which is endemic to China, has a limited distribution and a small population in the Taklimakan Desert. In this study, we described the breeding biology and nestling growth patterns of this understudied species. Eleven nests were monitored over three consecutive breeding seasons (2017–2019). The Xinjiang ground-jay breeding season extends from March to May with a clutch size of two or three. The incubation period was 18 d, and females spent most of their time incubating their eggs (63 %), followed by collecting leaves (25 %), resting (10 %), turning the eggs (1 %), grooming (0.6 %), and being vigilant (0.4 %). Both parents fed the nestlings with similar feeding frequencies and durations. The growth curve of the nestlings was S-shaped, and the parameters related to nestling mortality, such as tarsus length, showed faster growth than others. Over the three breeding seasons, 32 eggs were laid across 11 nests. Fifteen (47 %) eggs hatched, and 12 hatchlings across six nests fledged (37.5 %). Our study provides detailed information on the breeding biology and nestling growth of the Xinjiang ground-jay. Given its low reproductive success rate, small population size, and limited distribution, this bird species, which is endemic to China, requires further research, and its conservation should be prioritized.

Variation in bill surface area is associated with local climatic factors across populations of the plain laughingthrush.

Recent studies have found that avian bill and tarsus morphology may have evolved in response to climatic conditions, and these organs play important roles in thermoregulation and water retention in extreme environments. Here, we examined whether bill surface area and tarsus length were associated with climatic conditions in the plain laughingthrush, Garrulax davidi, which mainly occurs in north China and occupies several climatic zones from east to west. We measured bill surface area and tarsus length in 321 adults from 11 populations, almost encompassing all habitat types of the species. We analyzed the relationships among these morphological traits and local climatic factors. Bill surface area was positively correlated with maximum temperature, indicating that bill surface area tended to be larger in hotter environments. Furthermore, we found a negative relationship among bill surface area and winter precipitation, indicating that bill surface area tended to be larger in arid areas. However, we did not find any relationships between tarsus length and climatic factors. These results suggest that local climates may shape the evolution of bill morphology divergence, and summer seems to be the critical season for thermoregulation in this temperate zone passerine.

Morphological diversity and altitudinal differentiation of Aethopyga species.

The morphological characteristics of birds are an important tool for studying their adaptation and evolution. The morphological evolution of a clade is not only constrained by the phylogenetic relationship, but also influenced by ecological factors and interspecific competition. Aethopyga is a group of small nectar-eating birds with obvious sexual dimorphism. They have slender and decurved beaks, which reflect their unique diet and foraging mode. Traditional and geometric morphometrics were combined to characterize the body morphology and beak shape of six species of Aethopyga distributed in China. We aim to assess the roles of phylogeny, altitude, and species interactions to morphological evolution. The main distinguishing characteristic among these six species were overall body size, the ratio of body weight, culmen and tarsal length to body length, tail length and wing length, and beak shape (slender/straight vs. thick/decurved). Although these dimensions cannot distinguish all species, they can show a clear distribution trend, and there is a significant Mahalanobis distance between each pair of species. There were no significant phylogenetic signals in morphological traits. The results of PGLS analysis show that altitude is significantly correlated with log-transformed tarsus length and beak-shaped PC1 (slender/straight vs thick/decurved dimensions) across the six species analyzed. Mantel test shows that the distance matrix of beak morphological characteristics showed a significant correlation with the altitudinal distance matrix. The results indicated no significant phylogenetic signal in the morphological characteristics of six species. In terms of beak shape, species with greater overlap in elevation distribution have more similar morphological characteristics, that is, less morphological differentiation.

Ecological predictors of interspecific variation in bird bill and leg lengths on a global scale.

Bills and legs are two vital appendages for birds, and they exhibit huge interspecific variation in form and function, yet no study has examined the global predictors of this variation. This study examined global gradients in the relative lengths of bird bills and tarsi (i.e. exposed leg parts) to body size across non-migratory birds, while accounting for phylogeny. We found that relative bill length and tarsus length were related to diet, habitat density, latitude, annual mean temperature, temperature variability and hand-wing index (HWI), a proxy for birds' flight efficiency. Among these factors, diet played a primary role in predicting bill length, with nectar-feeding pollinators, vertivores, invertivores and omnivores having longer bills; HWI emerged as the predominant predictor of tarsus length, wherein species with higher HWI had shorter tarsi. However, the effects of these factors differed between passerines and non-passerines, with some temperature-related effects exhibiting opposite trends between these two groups. Our findings highlight the compromise in adaptations for feeding, thermoregulation and flight performance between the two distinct appendages.

Relationships Between Morphological Characteristics of Roosters in Broiler Breeders at Different Age Periods

The aim of study was to determine the relationships between morphological characteristics of roosters and fertility in broiler breeders at different age periods. A total of 48 roosters and 480 hens Ross 308 broiler breeder were used. The body weight, comb width and length, wattle width and length, and tarsus length of roosters were measured for morphological characteristics at 42, and 53 weeks of age. A total of 1500 eggs were incubated at 37.7 °C and 50-55% relative humidity for 18 d, then eggs were incubated at 36.6 °C and 60% relative humidity for 3 d. The effect of age on comb length, comb index (P=0.002), wattle width (P=0.008), wattle area (P=0.015) and tarsus length were found significant (P=0.000). There were correlations between body weight and fertility at 53 weeks of age (r = 0.663; P<0.05). There was no correlation between fertility and comb length, comb width, comb area, comb index, wattle width, wattle area, wattle index, and tarsus length at 42 and 53 weeks of age (P>0.05). In conclusion; some characteristics based on external appearance are used for male selection in broiler breeders, but no relationship was found between investigated morphological characteristics and fertility, except for body weight.

Morphometric Variation in Lepidogrammus cumingi and Dasylophus superciliosus from Greater Luzon, Philippines based on Museum Specimens

The monotypic Scale-feathered Malkoha Lepidogrammus cumingi (Fraser 1839) and polytypic Red-crested Malkoha Dasylophus superciliosus (Dumont 1823) are two of the endemic cuckoos in the Philippines. The taxonomy and distribution of these endemic cuckoos are poorly known. Recent distribution data of these cuckoos showed broader distribution patterns in the islands of Luzon, Catanduanes, and Marinduque; however, morphometric variations among these island populations are still unknown. While both species are sexually monomorphic, the differences between sexes were mainly based on plumage coloration. Dasylophus superciliosus is composed of two subspecies: ssp. superciliosus (Southern Luzon) and ssp. cagayanensis (Northern Luzon). The separation of the two subspecies of D. superciliosus was determined by the differences in superciliary feather, the coloration of breast plumage, and the tail band. In this study, we investigated the morphometric variations (1) between subspecies of D. superciliosus, (2) among island populations, and (3) between sexes (sexual dimorphism) of the two malkoha species. Four linear measurements (bill length, wing length, tarsus length, and tail length) were measured from 184 museum specimens. Results showed that the Catanduanes group (n=10) of L. cumingi exhibited a smaller body size than the Marinduque group (n=9). Red-crested Malkoha D. superciliosus showed significant differences between its two subspecies where the ssp. cagayanensis (n=28) exhibited smaller body size (bill length, wing length, and tail length) compared to ssp. superciliosus (n=81). Lastly, this study confirms that the two malkoha species are sexually monomorphic based on the analyzed morphometric data.

Long‐term series of measurements of eggs and chicks of Caspian terns (Hydroprogne caspia) breeding in Lake Chany, Western Siberia, Russia, during 1985 and 2011

AbstractCaspian terns (Hydroprogne caspia Pallas, 1770) present a sub‐cosmopolitan but scattered distribution, and many of its colonies are in a vulnerable state. The species has been listed in the Red Data Book of the Russian Federation and is covered by the Agreement on the Conservation of African‐Eurasian Migratory Waterbirds. We observed the colonies of Caspian terns repeatedly in the breeding season from May to June on the islands of Lake Chany from 1985 to 2011. We recorded clutch size, eggshell coloration and measured egg length and width to the nearest 0.1 mm with a caliper. Furthermore, we recorded the fate and hatching date of individual eggs and determined the clutch initiation date. Head, bill, tarsus length, and body weight of newly hatched chicks were measured. Caspian tern colony size changed between years from 50 nests in 1985 to 513 in 1999; therefore, the sample size of measured eggs varied from 90 to 1045. A total of 4137 eggs and 570 chicks were measured. We provide new information for this species nesting in west Siberia, which is important to compare with other local results. The presented data set is a novel long‐term data set on an isolated population of this species in center of Eurasian continent. The complete data set for this abstract published in the Data Article section of the journal is available in electronic format in MetaCat in JaLTER at http://db.cger.nies.go.jp/JaLTER/metacat/metacat/ERDP-2023-02.1/jalter-en.

Are animal personality, body condition, physiology and structural size integrated? A comparison of species, populations and sexes, and the value of study replication.

A major question in behavioural ecology is why behaviour, physiology and morphology are often integrated into syndromes. In great tits, Parus major, for example, explorative males are larger (vs. smaller) and leaner (vs. heavier) compared to less explorative individuals. Unfortunately, considerable debate exists on whether patterns found in specific studies are replicable. This debate calls for study replication among species, populations and sexes. We measured behavioural (exploration), physiological (breathing rate) and morphological traits (body mass, tarsus length, wing length, bill length) in two species (great vs. blue tits Cyanistes caeruleus), two populations (Forstenrieder Park vs. Starnberg) and two sexes (males vs. females). We then tested whether the same pattern of integration characterized all unique combinations of these three biological categories (hereafter called datasets). We used a multi-year repeated measures set-up to estimate among-individual trait correlation matrices for each dataset. We then used structural equation modelling to test for size-dependent behaviour and physiology, size-corrected (i.e. size-independent) behaviour-physiology correlations and size-corrected body mass-dependent behaviour and physiology. Finally, we used meta-analyses to test which structural paths were generally (vs. conditionally) supported (vs. unsupported). We found general and consistent support for size-dependent physiology and size-corrected body mass-dependent physiology across datasets: faster breathers were smaller but heavier for their size. Unexpectedly, condition-dependent behaviour was not supported: explorative birds were neither leaner, nor was this relationship heterogeneous across datasets. All other hypothesized patterns were dataset-specific: the covariance between size and behaviour, and between behaviour and physiology differed in sign between datasets, and both were, on average, not supported. This heterogeneity was not explained by any of our moderators: species, population or sex. The specific pattern of size- and condition-dependent physiology reported for a unique combination of species, population, and sex, thus generally predicted those in others. Patterns of size- or condition-dependent behaviour (i.e. 'personality'), or behaviour-physiology syndromes reported in specific datasets, by contrast, did not. These findings call for studies revealing the ecological background of this variation and highlight the value of study replication to help understand whether patterns of phenotypic integration reported in one study can be generalized.

Morphometrics, Habitat and Breeding Activity of Asian Common Toad, <i>Duttaphrynus melanostictus</i>, in Pakistan

The scientific data on ecology of amphibians from Pakistan are scarce. Asian Common Toad (Duttaphrynus melanostictus) is widely distributed in South Asia, and has been introduced outside its range causing severe ecological problems. We gathered data on morphometrics, habitat and breeding activity of the species in its western edge, North Punjab, Pakistan, of the range. The morphometric measurements of Asian Common Toad showed that the males were 49 ± 3.4 mm in snout vent length while the females were 58 ± 5.5 mm. Of the 13 measurements tested, the factor analysis produced five (head width, forelimb length, femur length, width of upper eyelid and foot length) significant measurements (r 0.80) for male while six (snout-vent length, head width, head length, greatest tympanum diameter, forelimb length, length of tarsus and foot) for female. The substrate of the habitat of Asian Common Toad was recorded as muddy to stony; water with neutral to slightly alkaline pH; dominated by herbs: Cannabis sativa, Parthenium hysterophorus; shrubs: Dodonaea viscosa, Lantana camara; grasses: Cynodon dactylon, Dactyloctenium aegyptium; and hydrophytes Alternanthera sessilis and Centella asiatica. The mean air and water temperature (day) during the breeding period were 27 – 30.5 and 25 – 28.5°C, respectively. The toad species laid eggs in small sized pools with lentic to slow-moving water with the mean depth of 32 – 64 cm. The males were more abundant than females (2.14♂:1♀) at the breeding sites. The advertisement call was of 9.3 ± 0.80 sec duration with a single note and 49.5 ± 6.5 nodes, –7.45 ± 0.95 average amplitude, 776 ± 51.8 Hz minimum frequency and 7011 ± 1680 Hz maximum frequency.

The Role of Food Quantity and Prey Type in Nestling Development of American Kestrels

ABSTRACT Diet is an important component of life history that can vary with, and ultimately determine, individual variation in phenotypically plastic traits. American Kestrels (Falco sparverius) generally have low post-fledging survival rates, which suggests a need to better understand what ecological factors, such as diet, influence nestling maturity. The generalist diet of kestrels makes it unlikely that all nestlings in a population receive the same diet. We investigated how breeding phenology and nestling sex ratio interact with diet metrics (diet diversity, percentage of prey types, rate of prey biomass delivery) and relate to nestling maturity (mass, tarsus length, wing length, hematocrit, hemoglobin concentration). We hypothesized that: (1) phenology and nestling sex ratio would correlate with inter-nest diet variation; (2) diet metrics would be predictive of nestling development; and (3) the manipulation of food quantity through food supplementation would lead to nestlings with greater developmental maturity. We found that inter-nest variation in diet was correlated with breeding phenology and nestling sex ratio, independently. However, the variation in diet was unrelated to nestling maturity. In response to food supplementation, kestrel parents decreased their food-provisioning rate, indicating that food quantity regulates parental care. Male nestlings appeared to benefit from supplementation while females did not. Our data demonstrated high inter-brood variation in nestling diet, and suggested that diet variation interacts with sex to influence growth and development of nestlings, which could potentially be linked to population decline.

Lower eyelid lengthening in facial nerve palsy: when is a periosteal flap required?

Background/aimsTo present a case series of patients with facial nerve palsy (FNP) undergoing lower eyelid surgery where inadequate horizontal tarsal length was encountered and managed with a periosteal flap.MethodsA two-centre...

Haemosporidian parasites in Antilophia galeata (Aves: Pipridae) in a Cerrado forest fragment

Haemosporidian parasites can cause pathogenic infections, leading to death or a reduction in the physical and reproductive abilities of the host. Several studies have identified haemosporidian infections in neotropical bird communities, but few have been conducted in populations, relating the infection to the biological attributes of the species. To determine haemosporidian prevalence in a population of Antilophia galeata and to assess factors that may be associated with parasitaemia, we analysed blood smears of 62 individuals from a Cerrado forest fragment. For each individual, the body mass, length of tarsus, sex, presence/absence of brood patch and feather moult were recorded. In total, 33 (53.2%) individuals were infected with haemosporidian parasites, 32 (51.6%) were infected with Plasmodium spp. and one (1.61%) was infected with Haemoproteus sp. Parasitaemia was not related to seasons, sex, reproduction, moulting or body condition but correlated positively with total leucocyte count, suggesting that individuals may be effective in infection control. This population may be tolerant to haemosporidian parasites because, despite the high prevalence, parasitaemia was low and constant; this is a potentially chronic infection that showed no adverse effects on the parameters analysed in this population.

Long‐term increase in female body condition and its effect on reproduction in two European red‐listed species, Common Pochard (Aythya ferina) and Tufted Duck (Aythya fuligula)

Body condition of breeding females is an important driver of an individual's fitness and the consequent dynamics of populations. Long‐term changes in female body condition are likely to be affected by recent shifts in climatic and environmental conditions that can result in changes to population demography. To help explain the drivers shaping body condition during the incubation period and its consequences for reproductive success, we examined the long‐term pattern in the body condition of breeding females of two declining sympatric diving duck species: Common Pochard Aythya ferina and Tufted Duck Aythya fuligula. We analysed the data obtained from 139 females of Common Pochard and 251 females of Tufted Duck breeding on fishponds in South Bohemia, Czechia, between 2004 and 2020. We calculated the body condition index of females during late incubation based on the residuals from the relationship between body mass and tarsus length and used the incubation stage as an additional predictor of body mass. Body condition of both species did not decline over the 17 years of the study. The effect of winter weather conditions (winter temperature), water transparency (a proxy for food availability) and reproductive investment on body condition was not confirmed. Female body condition positively affected mean egg mass and hatchability in both studied species, i.e. females in better body condition laid larger eggs and hatched eggs with a higher hatching probability. We conclude that the population declines of the studied species are probably not connected to decreasing body condition of breeding females, but other reasons such as change in breeding propensity or offspring survival and recruitment should be considered in future studies.

Limited evidence that asymmetries of multiple Whiskered Auklet (Aethia pygmaea) feather ornaments could serve a display function

Elaborate avian feather ornaments have proven to be enigmatic because their function is often unclear, even though they are used in courtship and social displays. Male and female Whiskered Auklets Aethia pygmaea display on their faces four elaborate feather ornaments that serve both courtship and mechanosensory functions: three bilateral pairs of white facial plume tracts (superorbital, suborbital and auricular) and a slender black forehead crest, each consisting of several filoplumes. We studied left–right symmetry in the three antenna‐like bilateral white head plumes of 721 wild‐caught marked individuals (162 of known sex, 94 of known age that were 1–16 years old) during 1992–2009. Auricular and suborbital plumes were slightly more asymmetric in subadults (1‐year‐olds) than in adults (≥ 2 years old) but the opposite was true for superorbital plumes. Ornament asymmetries were not sexually dimorphic, nor were they significantly related to individual body condition, body size or age, except that superorbital plume asymmetry decreased significantly with tarsus length. Relative asymmetry (scaled for ornament size) of all three ornaments was negatively correlated with plume size, as predicted by some sexual selection models, but variation in asymmetries was large and differences between left (L) and right (R) sides in most birds were probably too small to be detected visually. Marginal mean absolute asymmetries (|L–R|) of super‐ and suborbital plumes were correlated with ocean climate during the preceding year when the birds would have been moulting, suggesting that fluctuating asymmetry at the population level might be a useful index of environmental stress in this seabird. The spectacular bilaterally expressed facial plumes displayed by Whiskered Auklets provide an interesting test case for questions about asymmetry in sexually and naturally selected traits.

Reproductive biology of the Whitehead’s Broadbill (Calyptomena whiteheadi)

ABSTRACT Whitehead’s Broadbill, Calyptomena whiteheadi, an endemic species on the island of Borneo, has a declining population, raising the question of whether reproduction might be a factor limiting population growth. We studied breeding biology based on 52 nests in Kinabalu Park, Sabah, Malaysian Borneo in 2009–2020. Length of the egg-laying season was 99 days with a median of 22 March. Clutch size was typical of tropical songbirds at 2.0 ± 0.13 eggs (SE). Nest success was relatively high at 52%, and daily nest predation rate was relatively low at 0.013 ± 0.004 (SE). Concordantly, length of incubation and nestling periods were relatively long at 19.0 ± 0.26 d and 26.8 ± 0.3 d (SE), respectively. Similarly, the growth rate constants (K) for mass, wing length and tarsus length were slow at 0.252, 0.161 and 0.188, respectively. Slow growth might result in part from their frugivorous diet, as we show using seed traps, but they are reported to include insects in their diets and food provided to their young. Feeding effort, as reflected by the number of fruit seeds dropped below the nest, increased through the nestling period. Brooding effort of parents for nestlings was high on hatch day and decreased until Day 10–15 when it stopped. Food and parental care efforts do not seem to cause their slow growth. Ultimately, our study population has reproductive success that suggests it is not limiting population growth, but studies are needed in other locations to determine if it is a problem elsewhere.

Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics

Biometric analysis allows the sexing of most vertebrates, particularly birds. Birds of prey, and, especially, the Bonelli's eagle (Aquila fasciata), show reverse sexual dimorphism (i.e., females are usually larger than males). In contrast to blood sampling, the use of morphometrics allows sex determination using a non-invasive method, and, therefore, it facilitates fieldwork. By means of a linear discriminant analysis of biometric variables, we obtained different equations that allow the sexing of nestlings and adult Bonelli's eagles. We sampled 137 Bonelli's eagles, 82 nestlings and 55 adults in eastern Spain during the period 2015-2022. The sexes obtained after linear discriminant analysis were compared with their molecular sexing. The validation procedure of the linear discriminant equations facilitated the reduction of the number of variables used and, consequently, optimised working time and sexing accuracy. After validation, some equations showed a 100% sexing efficiency for Bonelli's eagles, particularly for adults. Our results showed that the variables with smaller overlap between the sexes were the lateral tarsus length and dorso-ventral tarsus length, particularly in nestlings. The rest of the variables showed some overlap between the sexes in both age classes. The results we obtained enable the sexing of juvenile and adult Bonelli's eagles in the field using just these two measurements. Hence, this is an easy, accurate, quick and non-invasive method with multiple applications, including in studies on population dynamics, survival analysis or extinction risk assessments, which, ultimately, could contribute to the improvement of the conservation status of this endangered species.

Allometry reveals trade-offs between Bergmann’s and Allen’s rules, and different avian adaptive strategies for thermoregulation

Animals tend to decrease in body size (Bergmann’s rule) and elongate appendages (Allen’s rule) in warm climates. However, it is unknown whether these patterns depend on each other or constitute independent responses to the thermal environment. Here, based on a global phylogenetic comparative analysis across 99.7% of the world’s bird species, we show that the way in which the relative length of unfeathered appendages co-varies with temperature depends on body size and vice versa. First, the larger the body, the greater the increase in beak length with temperature. Second, the temperature-based increase in tarsus length is apparent only in larger birds, whereas in smaller birds, tarsus length decreases with temperature. Third, body size and the length of beak and tarsus interact with each other to predict the species’ environmental temperature. These findings suggest that the animals’ body size and shape are products of an evolutionary compromise that reflects distinct alternative thermoregulatory adaptations.

Differences in bird community structure between riparian and upland zones in a New Guinean rainforest

Riparian forests serve as important habitats that enhance diversity of bird species and perform crucial ecosystem functions in tropical forest landscapes. We compared the community structure (represented by functional trait composition) and diversity (represented by Shannon index) of birds in riparian and upland zones in a semi-continuous primary rainforest in Papua New Guinea. Distance sampling was applied to provide unbiased abundance estimates. Bird community structure was examined by principal coordinate analysis of neighbour matrices (PCNM) in the Canoco 5 program. Analysis of diversity was performed using mixed-effects linear models in R 3.5.1. Species diversity was marginally higher in riparian zones (P = 0.065). Community structure differed significantly in riparian and upland zones (P = 0.008). Invertivorous and omnivorous birds preferred riparian habitats but frugivorous and nectivorous birds avoided riparian zones. Birds in riparian zones were characterised by preferences for high-density forest interior but birds in upland areas mostly occupied exposed canopy layers. Beak dimensions were greater in riparian zones but body mass, and lengths of wing and tarsus were greater in upland zones. Species found in riparian zones had greater geographical ranges than those in upland zones. Our results highlight the adaptability of a rainforest bird community to natural disturbances characterised by localised river flooding and riverbank erosion. For example, small invertivorous and omnivorous birds can navigate disturbed vegetation and exploit river-associated invertebrate food supply while moving to alternative food sources during intensive flooding. On the other hand, large frugivorous and nectarivorous birds are mostly sedentary and require an intact canopy layer for foraging, responding poorly to changes in vegetation structure. By moving beyond species-level relationships when examining bird community structure, we were able to better interpret and connect our findings with other studies on bird communities in tropical rainforest.

Morphometric and Internal Measurement of African Mourning Doves at Elssuki Area, Sinnar State Sudan

The African Mourning Dove (Streptopelia decipiens decipiens) is the most widespread species of Columbidae in Africa. There is little research done on this species in Sudan. This study was conducted in 15/12/2016 to 29/3/2017, at Elssuki area, N 13 19 0 E 33 52 60, Sinnar state, Sudan. The aims of this study are to assess the morphometric (body weight, bill, tarsus, tail, wing, head and culmen length) and physiological variation of African mourning dove (Streptopelia decipiens decipiens). Twenty birds were captured by traditional traps from Alssuki city and around Hamadna allah village 11 km from Elssuki. Morphological measurement like body weight, the tall of the tail, bill, bill with ahead, wings and tarsus were measured using ruler and registered in a sheet. Internal parts were also measures, the tall of intestine and kidneys, the heart, liver and gizzard were weighed using sensitive balance. There is significant variation between the bird in body weight, the tall of morphological feature and external one. The sample from Hamadna allah reflect higher weigh and of tall of both internal or external parts. It was agreed with some studies in other parts of the world of morphometric variation but on other hands showed that there is a relationship between body weight and some internal parts like gizzard weight. The difference may be attributed to genetic characters, or type, or availability of food or food quality, and habitat differentiation.

Sexual dimorphism in body size and some exterior traits of pigeon breed groups

In this study, sexual dimorphism in pigeons was investigated. Rensch's rule was evaluated across pigeon breeds. Body weight, body length, beak length, wingspan, tail length, and tarsus length were used for the analysis. We have divided the breeds in the five groups (form, frills and owls, tumbler and rollers, homer and highflyer, feral). The allometric relation in the traits between female and male measures were analyzed. The measure of sexual size dimorphism was measured for each trait as a simple male size divided by female size (Sexual Size Index, SSI). On average across traits, male birds have higher values than female birds, both across breed groups and overall. No deviation from isometric allometry can be observed except the tail length. No trends towards logarithmic female values according to the SSI could be identified. According to the results, the rules of Rensch for pigeon breeds are rejected. Sexual dimorphism exists between breeds and traits, mainly in favor of the male birds. In most cases, allometric relationships between breeds change, as do traits.