Males in seemingly female‐like plumage do not mimic females: UV reflectance reveals temporal cryptic dimorphism in a manakin species exhibiting delayed plumage maturation

Manakins (Pipridae) are neotropical birds that usually exhibit delayed plumage maturation (DPM). Thus, while plumage of most adult male manakins is brightly conspicuous, subadult males and females are basically dull‐olive green. Although sexual dichromatism in some bird species may be evident only through UV reflectance, this phenomenon, known as hidden sexual dichromatism, has not been previously studied in manakins to compare subadult males and females. Within this framework, we carried out spectrophotometric analyses in searching for hidden sexual dichromatism in the white‐bearded manakin Manacus manacus, through comparison of UV spectra in females and subadult males in green plumage. Our results revealed UV reflectance in both sexes in green plumage. Moreover, we found UV spectral differences in homologous color patches between sexes, particularly at belly. Since the observed differences may allow intraspecific sex recognition of individuals in green plumage, our results do not support the female‐mimicry hypothesis to explain delayed plumage maturation in the white‐bearded manakin. Although our findings dismiss the female mimicry hypothesis, we cannot state whether these results support the non‐mutually exclusive cryptic and status signaling hypotheses. We propose then, that dull coloration of subadult males may serve both as a cryptic trait and to limit the energetic costs of acquiring the adult plumage before sexual maturity. Meanwhile, differential UV color traits between sexes in green plumage may allow adult males to avoid unnecessary energy expenditures in courtship displays in the presence of males near leks, and to selectively focus their the courtship displays on females. In accordance with the status signaling hypothesis, subadult males can be recognized both as males and subordinates and consequently may practice courtship displays without suffering aggressions by adult males. Our results highlight the importance to include a wider range of spectrophotometric information analyses for testing hypotheses regarding delayed plumage maturation.     

Weak genetic structuring indicates ongoing gene flow across White-ruffed Manakin (<Emphasis Type="Italic">Corapipo altera</Emphasis>) populations in a highly fragmented Costa Rica landscape

We explored the effects of recent forest fragmentation on fine-scale patterns of population structuring and genetic diversity in populations of White-ruffed Manakins (Corapipo altera) inhabiting premontane forest fragments of varying size in southwestern Costa Rica. Habitat fragmentation is a major conservation concern for avian populations worldwide, but studies of the genetic effects of fragmentation on Neotropical birds are limited. We sampled 159 manakins from nine forest fragments of varying size within an 18 km radius, and genotyped these birds at 13 microsatellite loci. Bayesian clustering methods revealed that birds from all fragments comprised a single genetic population, and an MCMC approach showed that the fragments were likely to be at migration-drift equilibrium. F-statistics showed only modest levels of differentiation between forest fragments. We calculated allelic diversity indices for each fragment but found no correlation between genetic diversity and fragment size. These results suggest that manakins may retain substantial connectivity via inter-fragment dispersal despite habitat fragmentation.     

Adaptations for avian frugivory: assimilation efficiency and gut transit time of Manacus vitellinus and Pipra mentalis

Summary I examined the digestive physiology of two avian frugivores, the golden-collared manakin, Manacus vitellinus, and the red-capped manakin, Pipra mentalis, to discover how these birds extract energy from fruit. Using 14 species of fruit in the natural diet of manakins, I examined the assimilation of nutrients from fruit pulp, fruit passage rates, seed passage rates, and gut morphology. Fruits in the manakins' diets had high water content (average, 84%) and low nutrient concentrations (3 kJ/g wet pulp; 17 kJ/g dry pulp; 1% nitrogen/g dry pulp). Manacus and Pipra did not differ in the average assimilation of energy in fruit pulp (63%), although it varied from 37 to 84% depending on fruit species. Assimilation of total nonstructural carbohydrates in the fruit pulp was very high (86–98%) in both species. Gut evacuation was rapid; maximum transit time of a labeled fruit was 30 min. Seeds passed through the gut faster (Manacus: 15 min; Pipra: 12 min) than the accompanying fruit epidermis (both spp: 22 min). Manakins regurgitated large seeds (>5 mm diameter) in 7 to 9 min. Rapid gut passage time, high assimilation of nonstructural carbohydrates, and the selective regurgitation and rapid elimination of bulky seeds enable manakins to process a large volume of food per day. By increasing rates of fruit intake and gut passage, manakins can effectively increase total nutrient uptake. These adaptations of manakins are requisite for harvesting sufficient nutrients from fruit, due to its low nutrient density, high water content, and bulky seeds.     

Morphometric sex determination of young Ospreys Pandion haliaetus using discriminant analysis

Capsule Discriminant functions based on morphometric variables provide a reliable method for sex identification of free‐living and hacked young Ospreys.

Aims To describe an easy, accurate and low‐cost method for sex determination of fully grown nestling and fledgling Ospreys Pandion haliaetus based on morphometric measurements.

Methods Four different measurements were taken in 114 birds (40–73 days old) and a DNA analysis, using PCR amplification, was carried out for sex identification. A forward stepwise discriminant analysis was performed to build the best explanatory discriminant models, which were subsequently validated using statistics and external samples.

Results Our best discriminant function retained forearm and tarsus as the best predictor variables and classified 95.1% of the sample correctly, supported also by external cross‐validations with both hacked and free‐living birds. Moreover, a discriminant function with only forearm as predictor showed a similar high correct classification power (93.4%).

Conclusions These discriminant functions can be used as a reliable and immediate method for sex determination of young Ospreys since they showed high discriminant accuracy, close to that of molecular procedures, and were supported by external cross‐validations, both for free‐living and hacked birds. Thus, these morphometric measurements should be considered as standard tools for future scientific studies and management of Osprey populations     

Sex determination in the Lesser Flamingo (Phoenicopterus minor) using morphological measurements

Morphological measurements and blood samples were taken from 154 Lesser Flamingos Phoenicopterus minor, including adults (>3 years old), immature sub-adults (2–3 years old) and first-year juvenile birds of both sexes, captured at Lake Bogoria, Kenya (0°11'–20' N, 036°06' E) during 2001 and 2002. PCR amplification of the CHD-Z and CHD-W genes using DNA extracted from the blood samples was used to determine the sex of each bird. There were significant differences in mass and tarsus length among the three age groups, indicating that Lesser Flamingos continue to grow in skeletal size and mass between fledging and the attainment of adult plumage at 3–4 years of age. On average, males were significantly larger than females in all age groups, although there was substantial overlap between the sexes in all morphological measurements. The element with the least amount of overlap was head-and-bill length. Discriminant functions utilising head-and-bill length that correctly predict the sex of juvenile and immature birds with approximately 93% accuracy are presented. By adding total tarsus length, the sex of wild adult Lesser Flamingos is correctly predicted with approximately 98% accuracy. The same discriminant function developed for wild adult birds predicted the sex of 19 captive adult Lesser Flamingos of known sex with 100% accuracy.     

Differentiation of subspecies and sexes of Beringian Dunlins using morphometric measures

Five subspecies of Dunlins (Calidris alpina) that breed in Beringia are potentially sympatric during the non‐breeding season. Studying their ecology during this period requires techniques to distinguish individuals by subspecies. Our objectives were to determine (1) if five morphometric measures (body mass, culmen, head, tarsus, and wing chord) differed between sexes and among subspecies (C. a. actites, arcticola, kistchinski, pacifica, and sakhalina), and (2) if these differences were sufficient to allow for correct classification of individuals using equations derived from discriminant function analyses. We conducted analyses using morphometric data from 10 Dunlin populations breeding in northern Russia and Alaska, USA. Univariate tests revealed significant differences between sexes in most morphometric traits of all subspecies, and discriminant function equations predicted the sex of individuals with an accuracy of 83–100% for each subspecies. We provide equations to determine sex and subspecies of individuals in mixed subspecies groups, including the (1) Western Alaska group of arcticola and pacifica (known to stage together in western Alaska) and (2) East Asia group of arcticola, actites, kistchinski, and sakhalina (known to winter together in East Asia). Equations that predict the sex of individuals in mixed groups had classification accuracies between 75% and 87%, yielding reliable classification equations. We also provide equations that predict the subspecies of individuals with an accuracy of 22–96% for different mixed subspecies groups. When the sex of individuals can be predetermined, the accuracy of these equations is increased substantially. Investigators are cautioned to consider limitations due to age and feather wear when using these equations during the non‐breeding season. These equations will allow determination of sexual and subspecies segregation in non‐breeding areas, allowing implementation of taxonomic‐specific conservation actions.     

Competing Females and Caring Males. Polyandry and Sex-Role Reversal in African Black Coucals, Centropus grillii

Most species of birds show bi‐parental or female‐only care. However, a minority of species is polyandrous and expresses male‐only care. So far, such reversals in sex roles have been demonstrated only in precocial bird species, but there was suggestive evidence that such a mating system may occur in one altricial bird species, the black coucal, Centropus grillii. In a field study in Tanzania we investigated whether black coucals are sex‐role reversed and polyandrous. We found that males were mated to one female, rarely vocalized and provided all parental care from incubation of eggs to feeding of young. In contrast, female black coucals were about 69% heavier and 39% larger than males and polyandrous. They spent a large proportion of time calling from conspicuous perches, defended breeding territories, did not help in provisioning young and had a higher potential reproductive rate than males. We conclude that the black coucal currently represents the only altricial bird species with sole male parental care and a classical polyandrous mating system. High nest predation pressure and small territory sizes due to high food abundance may have been important factors in the evolution of sex‐role reversal and polyandry in this species.     

A robust tool highlights the influence of bird migration on influenza A virus evolution

One of the fundamental unknowns in the field of influenza biology is a panoramic understanding of the role wild birds play in the global maintenance and spread of influenza A viruses. Wild aquatic birds are considered a reservoir host for all lowly pathogenic avian influenza A viruses (AIV) and thus serve as a potential source of zoonotic AIV, such as Australasian‐origin H5N1 responsible for morbidity and mortality in both poultry and humans, as well as genes that may contribute to the emergence of pandemic viruses. Years of broad, in‐depth wild bird AIV surveillance have helped to decipher key observations and ideas regarding AIV evolution and viral ecology including the trending of viral lineages, patterns of gene flow within and between migratory flyways and the role of geographic boundaries in shaping viral evolution (Bahl et al. 2009 ; Lam et al. 2012 ). While these generally ‘virus‐centric’ studies have ultimately advanced our broader understanding of AIV dynamics, recent studies have been more host‐focused, directed at determining the potential impact of host behaviour on AIV, specifically, the influence of bird migration upon AIV maintenance and transmission. A large number of surveillance studies have taken place in Alaska, United States—a region where several global flyways overlap—with the aim of detecting the introduction of novel, Australasian‐origin highly pathogenic H5N1 AIV into North America. By targeting bird species with known migration habits, long‐distance migrators were determined to be involved in the intercontinental movement of individual AIV gene segments, but not entire viruses, between the Australasian and North American flyways (Koehler et al. 2008 ; Pearce et al. 2010 ). Yet, bird movement is not solely limited to long‐distance migration, and the relationship of resident or nonmigratory and intermediate‐distance migrant populations with AIV ecology has only recently been explored by Hill et al. ( 2012 ) in this issue of Molecular Ecology. Applying a uniquely refined, multidimensional approach, Hill et al. validate the innovative use of stable isotope assays for qualifying migration status of wild mallards within the Pacific flyway. The authors reveal that AIV prevalence and diversity did not differ in wintering mallard ducks with different migration strategies, and while migrant mallards do indeed introduce AIV, these viruses do not circulate as the predominant viruses in resident birds. On the other hand, resident mallards from more temperate regions act as reservoirs, possibly contributing to the unseasonal circulation and extended transmission period of AIV. This study highlights the impact of animal behaviour on shaping viral evolution, and the unique observations made will help inform prospective AIV surveillance efforts in wild birds.     

Triploidy in a sexually dimorphic passerine provides new evidence for the effect of the W chromosome on secondary sexual traits in birds

In birds, there are two main models for the determination of sex: the ‘Z Dosage’ model in which the number, or dose, of Z chromosomes determines sex, and the ‘Dominant W’ model which argues that a specific gene in the W chromosome may influence Z gene expression and determine sex. The best evidence for W determination of sex comes from birds with 2 copies of the Z chromosome paired with a single W (e.g. ZZW) which are nonetheless females. Here, we expand the species where such a mechanism may operate by reporting a case of a triploid Neotropical passerine bird with sexually dimorphic plumage, the São Paulo marsh antwren Formicivora paludicola. Evidence from 17 autosomal unlinked microsatellite loci, and CHD1 sex‐linked locus, indicate that this individual is a 3n ZZW triploid with intermediate plumage pattern. This example expands our knowledge of sex determination mechanisms in birds by demonstrating that both the W and the two Z chromosomes affect the expression of morphological secondary sexual traits in a non‐galliform bird.     

Nest site availability and niche differentiation between two cavity‐nesting birds in time and space

Niche differentiation is a key concept in the field of ecology and refers to the process by which competing species within an ecological community partition utilization of environmental resources to achieve coexistence. The existence of niche differentiation is uniquely difficult to prove on account of the fact that historical interaction among species, which plays a key role in elucidating the current state of coexistence among species, is not well known. We created continuous niche gradients in nest‐site resources between two sympatric secondary cavity‐nesting birds, the green‐backed tit (Parus monticolus) and the russet sparrow (Passer cinnamomeus), and investigated whether nesting site is a factor contributing to limiting breeding overlap by regular inspection and 388,160 min of film recording. Our results indicate that although we manipulated nest site availability to be uniformly high along the habitat gradient, the two bird species have little overlap in nest sites and rarely compete for them. Furthermore, the green‐backed tit possessed a wide range of fundamental niche that covered that of the russet sparrow, while their reproductive time was largely segregated. The sparrow was more aggressive and outcompeted the tit in their overlapped range. These results suggest that even though nesting sites are crucial to the reproduction of cavity‐nesting birds, some other factor plays a more important role in limiting niche overlap between sparrows and tits in space and time. Given that these two cavity‐nesting birds continued to use different habitats and breed in segregated time after our manipulation, their relationship is better explained by the ghost of competition past theory.     

A Young Manakin Knows His Place: Evidence for an Age‐Graded Dominance Hierarchy Among Long‐Tailed Manakins

In lek‐breeding systems where many males gather at display sites, males benefit from the establishment of dominance hierarchies to reduce intrasexual aggression and the associated risk of injuries. Long‐tailed manakins (Chiroxiphia linearis) exhibit an exploded lek‐breeding system wherein the two top‐ranking males at each display site team up to perform elaborate coordinated courtship displays for females. Young males undergo delayed plumage maturation whereby they acquire distinct pre‐definitive plumage patterns each year until they attain definitive plumage in their fifth year. This unique characteristic is thought to have evolved as a status‐signalling mechanism to aid in the establishment of an age‐graded dominance hierarchy in which older males are dominant to younger males. Previous research has shown evidence for such a dominance hierarchy among alpha and beta males; however, the presence of this hierarchy among males of other age classes has never been quantified. In this study, we investigated the presence of an age‐graded dominance hierarchy by determining whether older males direct more aggressive behaviours towards younger males. We also investigated whether status signalling is less clear within age classes than between age classes, by determining whether males within the same age class exhibit more aggression towards each other. We found that older males performed aggressive behaviours towards younger males much more frequently than younger males performed aggressive behaviours towards older males. We also found that some aggressive interactions occurred between males within the same age class more frequently than between males from different age classes. Our study provides some evidence for an age‐graded dominance hierarchy among male long‐tailed manakins of all age classes and also provides some support for the status‐signalling hypothesis. However, further research is needed to conclusively establish the presence of a linear dominance hierarchy among younger male manakins. This research may help us better understand the evolution of complex hierarchical systems in animals.     

Effects of migration distance and sex on stopover timing and refueling by Wilson's Warblers

Migration distance and sex are integral to avian migration strategies, yet these intrinsic factors are understudied with respect to their effects on stopover ecology and behavior. We investigated how individual variation in migration distance and sex affected body condition, refueling performance, and stopover durations of Wilson's Warblers (Cardellina pusilla) during spring and fall 2006 at a stopover site in southern Arizona. Migration distance of individuals was inferred using the hydrogen stable isotope ratio of feathers (δ²H_f) as an index of breeding latitude, refueling rate was assessed using plasma triglyceride and β‐OH‐butyrate, and minimum length of stay was estimated by re‐sighting color‐banded birds. In the spring, migration distance and sex were strong determinants of the timing of migration by Wilson's Warblers, with males and shorter‐distance migrants passing through the site earlier than females and longer‐distance migrants. Later‐arriving migrants also had higher fat scores and refueling rates. However, neither migration distance nor sex independently affected body condition (fat score or size‐corrected mass), refueling rate, or minimum length of stay. In a smaller sample of fall migrants, we found that longer‐distance migrants and males had higher refueling rates than shorter‐distance migrants and females. Our results show that differences in migration distance can, under some circumstances, affect how birds use stopover sites. Stable isotope analysis and other methods can provide information on migration distance, and should be integrated with measurements of timing, fuel stores, refueling performance, and departure behavior to gain a deeper understanding of bird migration.     

The role of farm structure on bird assemblages around a Kenyan tropical rainforest

Although it is clear that the farmlands neighbouring fragmented forests are utilized by some forest birds, it is not clear how birds in general respond to farmland habitat mosaic. An effort was made to determine how bird density and foraging assemblages were influenced by farm structural characteristics and distance from forest edge. Thirty farms up to a distance of 12 km around Kakamega forest in western Kenya were studied. Farm structure entailed size, hedge volume, habitat heterogeneity, woody plant density, plant diversity and crop cover. Birds were surveyed using line transects and DISTANCE analyses and classified into six feeding guilds and three habitat associations. Size of farms increased away from the forest, as woody plant density, plant diversity, indigenous trees and subsistence crop cover declined. The most important farm structure variable was hedge volume, which enhanced bird species richness, richness of shrub‐land bird species and insectivorous bird density (R = 0.58, P < 0.01). Bird density increased with tree density while indigenous trees were suitable for insectivores and nectarivores. There were very few forest bird encounters. Agricultural practices incorporating maintenance of hedges and sound selection of agroforestry trees can enhance conservation of birds on farmland, though, not significantly for forest species.     

Loss of sexual dimorphism is associated with loss of lekking behavior in the green manakin Xenopipo holochora

Manakins (Pipridae) are well know for elaborate male sexual displays and ornate plumage coloration, both of which are thought to have evolved as a consequence of lekking breeding, the prevalent mating system in the family. Less attention has been paid to a handful of ‘drab’ manakin species, in which sexual dimorphism appears to be reduced or absent. Using character reconstruction, we show that these ‘exceptions to the rule’ represent phylogenetically independent cases of losses in sexual dimorphism, and as such could provide a focal group to investigate the link between changes in morphology and in life history (e.g. mating system). We take a first step in this direction by focusing on two subspecies of the putatively monomorphic green manakin Xenopipo holochlora to formally confirm that the species is sexually monomorphic in size and plumage color and test the prediction that sexual monomorphism is associated with the loss of lekking behavior in this species. Our results show that size dimorphism is present but limited in the green manakin, with substantial overlap in male and female morphometric measures, and that sexes are largely monochromatic (including from an avian perspective), despite marked coloration differences between subspecies. Behavioral observations indicate that males do not form leks and do not engage in elaborate sexual displays, that there is no stable pair bond formation, and that females provide parental care alone. These findings are consistent with the idea that changes in mating behavior may have driven changes in morphology in Pipridae, and we encourage similar studies on other drab manakins to better understand this relationship.     

Avian Mobbing Response is Restricted by Territory Boundaries: Experimental Evidence from Two Species of Forest Warblers

Predator mobbing has been viewed as an adaptation to reduce the risk of predation, however, factors influencing mobbing behaviour are still debated. We report on the results of an experiment with Dendroica caerulescens and Dendroica virens designed to determine (1) whether mobbing response by forest songbirds during the breeding season is restricted by territory boundaries, (2) the distance songbirds will move in response to anti‐predator mobbing calls, and (3) whether reproductive status, age, and time of the breeding season determine the distance moved to mob. We did not detect an effect of reproductive status, age, or time of breeding season on the distance moved by birds to mob. All birds responded to the mobbing playback within their territory (defined by territorial defence in relation to specific song playbacks). The maximum distance moved within a territory to engage in mobbing ranged from 25 to 175 m ( = 72 ± 6 m). Three of 37 birds responded to playbacks outside their territory boundaries. In all three cases, maximum movement distances outside territories were short (25 m). Thus, for two species of warblers, mobbing is highly constrained by territory boundaries during the breeding season. This finding is congruent with arguments that mobbing is primarily a selfish behaviour, at least with respect to conspecifics. Our results also provide support for the ‘move‐on’ hypothesis.     

Does migration promote or restrict circumpolar breeding ranges of arctic birds?

Aim Migration has been suggested to promote large breeding ranges among birds because of the greater mobility of migratory compared with non‐migratory species, but migration has also been suggested to restrict breeding ranges because of evolutionary constraints imposed by the genetically based migration control programme. We aim to investigate the association between migration and the breeding ranges of both land birds and pelagic birds breeding in the Arctic region. Location The Arctic region. Methods Information on breeding and wintering ranges and migratory status of bird species breeding in the arctic tundra biome was compiled from the literature. The association between breeding range, migration distance and primary winter habitat was tested using multivariate generalized linear models and pair‐wise Mann–Whitney U‐tests. Phylogenetic effects were tested for using Mantel’s permutation tests. Results We found different relationships depending on the species’ major winter habitat. Among birds that are pelagic during winter, long‐distance migrants have the largest breeding ranges, while among terrestrial birds, residents and short‐distance migrants have the largest breeding ranges. Breeding ranges of coastal birds of all migratory distance classes are comparatively restricted. Main conclusions As a new explanation for this pattern we suggest that the possibility of colonizing large winter ranges is a key factor for the subsequent expansion of breeding ranges in arctic bird communities and possibly also in bird communities of other regions of the world. Because of the reversal in the relative extent of continents and oceans between the hemispheres, longitudinally wide winter ranges are more likely for long‐distance than short‐distance migrants among pelagic birds, while the reverse holds true for birds that use terrestrial winter habitats. For coastal birds both continents and oceans form barriers restricting colonization of extensive winter quarters and consequently also of extensive breeding ranges, regardless of the distance to the winter quarters.     

Seasonal abundance, reproduction and hunting of common quail Coturnix coturnix in the Eastern Cape Province, South Africa

This study investigated the potential overlap between breeding and hunting seasons for a population of common quail Coturnix coturnix in the Alexandria District. Seasonal abundance (assessed as the number of birds flushed per unit effort), sex ratios and reproductive condition (based on gonad sizes) of the quail were measured over a period of 16 months, including two hunting seasons. Hunting impacts were assessed in terms of the number of birds killed per unit of hunting effort. Quail exhibited a spring peak in abundance and reproduction, which coincided with the legal hunting season, and bird numbers varied markedly between years. Sex ratio varied, with males dominating early in spring. Hunters killed nearly 60% of the birds flushed, and hunter efficiency was positively correlated with the abundance of quail. These results confirm the dilemma for managers, as quail are currently hunted during the main breeding season and offtakes are high. The development of management strategies is hampered by a lack of understanding of the population biology and ecology, and impacts of hunting. A number of possible hunting strategies are discussed. Since current harvests may not be sustainable, further research is necessary.     

A new method for sexing Oriental White Storks

ABSTRACT.   For species where males and females are monomorphic, or nearly so, determining the sex of individual birds generally requires either capturing birds or collecting samples, such as feathers, for DNA analysis. We developed a new method, involving the use of photographs, to determine the sex of endangered Oriental White Storks ( Ciconia boyciana ). Using photographs, we analyzed the lateral features of the heads of 25 captive storks of known sex (12 males and 13 females) and found differences between males and females in the distance from the bill tip to the nape and the distance from the bill tip to the commissural point. These differences were used to generate a discriminant function that was then tested on 22 captive storks at Hyogo Homeland Park (Toyooka, Japan), and we correctly determined the sex of 18 individuals (82%). In addition, the sex of two wild storks was correctly assigned. Our results suggest that good-quality photographs can be useful for determining the sex of both captive and wild Oriental White Storks and, further, that similar methods may prove useful for determining sex in other species of birds.     

Sex determination of Red-tailed Hawks (Buteo jamaicensis calurus) using DNA analysis and morphometrics

ABSTRACT.   Currently, the sex of Red-tailed hawks ( Buteo jamaicensis ) cannot be determined by in-hand methods. Males and females do not differ in plumage and overlap in size. We collected feather samples and morphological measurements from migrating birds at four sites in the western United States. Sex was determined for individual birds using sex-specific DNA markers and polymerase chain reaction was used to identify these DNA markers. Using discriminant function analysis, we created equations for determining the sex of Red-tailed Hawks using in-hand measurements based on the DNA-determined sexes. We formed two equations, one for adults that was 98% accurate, and one for hatch-year birds that was 97% accurate. The ability to determine the sex of western Red-tailed Hawks using morphological measurements will be useful to investigators examining possible intra- or intersexual differences.     

The epidemiology underlying age‐related avian malaria infection in a long‐lived host: the mute swan Cygnus olor

Quantifying the factors that predict parasite outbreak and persistence is a major challenge for both applied and fundamental biology. Key to understanding parasite prevalence and disease outbreaks is determining at what age individuals show signs of infection, and whether or not they recover. Age‐dependent patterns of the infection of a host population by parasites can indicate among‐individual heterogeneities in their susceptibility to, or rate of recovery from, parasite infections. Here, we present a cross‐sectional study of avian malaria in a long‐lived bird species, the mute swan Cygnus olor, examining age‐related patterns of parasite prevalence and modelling patterns of infection and recovery. One‐hundred and fifteen swans, ranging from one to nineteen years old, were screened for infection with Plasmodium, Haemoproteus and Leucocytozoon parasites. Infections with three cytochrome‐b lineages of Haemoproteus were found (pooled prevalence 67%), namely WW1 (26%), which is common in passerine birds, and two new lineages closely related to WW1: MUTSW1 (25%) and MUTSW2 (16%). We found evidence for age‐related infection in one lineage, MUTSW1. Catalytic models examining patterns of infection and recovery in the population suggested that infections in this population were not life‐long – recovery of individuals was included in the best fitting models. These findings support the results of recent studies that suggest hosts can clear infections, although patterns of infection‐related mortality in older birds remain to be studied in more detail.