Determining the sex of Little Penguins (Eudyptula minor) in northern Bass Strait using morphometric measurements

In avian species with no obvious differences in plumage or body size between the sexes, such as penguins, discriminant function analysis (DFA) of morphometric measurements that display sexual dimorphism can provide a simple and rapid means of determining sex in the field. Like most other penguin species, the Little Penguin (Eudyptula minor) displays sexual dimorphism in bill shape and size. In the present study, discriminant functions (DFs) were developed for sexing adult Little Penguins at two colonies in northern Bass Strait, Victoria, Australia, and their accuracies were compared with those obtained previously in other parts of the species' range. Backwards stepwise DFA indicated that birds at Phillip Island can be sexed with an accuracy of 91% using a single measurement of bill depth (>13.33 mm classed as males). Similar analyses at Gibson Steps produced a DF incorporating bill length, bill depth and head length [although the model with the greatest accuracy when applied to birds from Phillip Island (91%) also contained only bill depth]. Published DFs derived in New Zealand had accuracies of 50–85% when applied to birds from Phillip Island and Gibson Steps, supporting earlier suggestions that DFs are not applicable across subspecies of the Little Penguin. In contrast, there was little difference between the accuracy of the DFs in the present study and that previously derived for the same subspecies in Tasmania when applied to birds from Phillip Island (89%) and Gibson Steps (92%). However, as the degree of variation in bill size within a subspecies is unknown it may still be prudent to derive colony-specific DFs.

Biometrics and sexing criteria of the yellow-faced honeyeater lichenostomus chrysops

Morphometric data on 99 adult and 13 juvenile Yellow-faced Honeyeaters Lichenostomus chrysops that were independently sexed using molecular techniques were analysed to investigate size dimorphism between the sexes. Our results support previous studies that have demonstrated Yellow-faced Honeyeaters are sexually dimorphic in size, with males being the larger sex. Discriminant analyses of morphometric data were used to develop a simple method for sexing adult Yellow-faced Honeyeaters in the hand. As five observers collected the measurements our sexing criteria are conservative and should have wide application for field ornithologists working on the species.

Methods for aging and sexing the Black-eared Miner, Manorina melanotis, and Yellow-throated Miner, M. flavigula

Morphometric data on 92 Black-eared Miners and 47 Yellow-throated Miners that had been independently sexed using molecular techniques were analysed to investigate size dimorphism between the sexes. We found that both species are sexually dimorphic in size, with males being the larger sex. Discriminant analyses of morphometric data were used to develop a simple method for sexing both species in the hand. Additionally, alula shape was consistent with other methods that we applied for ageing individuals. Sex-specific size differences between Black-eared and Yellow-throated Miners detected here add further support to the contention that they represent different taxa. The application of these sexing and ageing techniques for both species of mallee miner will improve ongoing field management of the endangered Black-eared Miner.

A morphological model for sexing nestling peregrine falcons (Falco Peregrinus Macropus) verified through genetic analysis

Adult peregrine falcons (Falco peregrinus macropus) have monotypic plumage and display strong reversed sexual dimorphism, with females significantly larger than males. Reversed sexual dimorphism is measurable among nestlings in the latter stages of their development and can therefore be used to differentiate between sexes. In the early stages of development, however, nestlings cannot be sexed with any degree of certainty because morphological differentiation between the sexes is not well developed. During this study we developed a model for sexing younger nestlings based on genetic analysis and morphometric data collected as part of a long-term banding study of this species. A discriminant function model based on morphological characteristics was developed for determining the sex of nestlings (n = 150) in the field and was shown to be 96.0% accurate. This predictive model was further tested against an independent morphometric dataset taken from a second group of nestlings (n = 131). The model correctly allocated sex to 96.2% of this second group of nestlings. Sex can reliably be determined (98.6% accurate) for nestlings that have a wing length of at least 9 cm using this model. Application of this model, therefore, allows the banding of younger nestlings and, as such, significantly increases the period of time over which banding can occur. Another important implication of this model is that by banding nestlings earlier, they are less likely to jump from the nest, therefore reducing the risk of injury to both the brood and the bander.

An evaluation of three field techniques for sexing live Gould's petrels (Pterodroma leucoptera) (Procellariidae)

Many petrels show no obvious sex-linked dimorphism in plumage or size and consequently many researchers fail to sex the living individuals they study. Several methods of sex discrimination that do not rely on plumage- or obvious size-dimorphism can be used to sex live petrels. The effectiveness of three such techniques was evaluated: body condition at the time of laying, cloacal inspection, and discriminant function analysis (DFA) of external morphometrics. Gould’s Petrel (Pterodroma leucoptera leucoptera) was used as the subject species. Sexing of breeding adults on the basis of body condition at laying proved to be highly accurate (100% of birds sexed correctly) but required detailed knowledge of the breeding biology. Following training, cloacal inspection proved to be an accurate (96%) method of determining the sex of breeding adults, but not of chicks. Unlike molecular sexing, the latter two methods of sex discrimination provide immediate knowledge of the sex of individuals in the field. DFA of external morphometrics predicted the sex of adults with an accuracy of 73% and the sex of near-fledged chicks with an accuracy of 66%. However, the probability of correct assignment of sex was low in most cases and, therefore, this is the least useful of the three techniques assessed here.

Morphological signals of sex and status in spotted bowerbirds

The Spotted Bowerbird, Chlamydera maculata, appears to be sexually monomorphic. We caught and marked 118 birds in central Queensland, and sexed 88 using molecular methods. We found that our catch was strongly male-biased, both at bower sites and at non-bower feeding sites. We continued to observe the bird's behaviour after their release and so sub-divided males into sexual status groups as either bower-owners or non-owners. We searched for morphological measures, subjectively judged colour differences and quantitatively collected spectral measures of the visual properties of the crest feathers that would allow us to separate birds of differing sex and status. We found that bower owners had larger crests than non-owner males or females and that crest area provided the most accurate predictor of a bird's sex and status in a discriminant function analysis. We studied a cohort of seven males who went from non-owners to bower owners over three years, and found that their change in status was accompanied by a change in crest size – the only significant change in their morphology. Crest size did not relate to the mating success of a bower-owner. Instead, we suggest why the crest may differ between status groups and the implications that this may have for the sexual behaviour of male and female Spotted Bowerbirds.

Sperm immobilizing properties of lemon juice

The aim of this study was to evaluate the sperm-immobilizing properties of lemon juice to determine if they are consistent with its traditional contraceptive use. It was found that lemon juice supernatant (LJS) has high osmolality (550–60 mOsm) and low pH (2.2–2.6) and that addition of LJS to semen to give a final concentration of 20% v/v reduced the pH from around 8.4 to 4.1. This acidification was associated with irreversible cessation of all sperm movements within 1 minute. In conclusion, lemon juice should be further evaluated for acceptability, safety, and efficacy as a topical vaginal contraceptive agent.

Validation of the aceto-carmine technique for evaluating phenotypic sex in Nile tilapia (Oreochromis niloticus) fry

In this study a method for evaluating phenotypic sex in Nile tilapia was validated. A technique that uses aceto-carmine squash mounts to stain the entire gonadal tissue for microscopic examination (Method 2- squash mounts) was compared with a technique based on traditional histology. Approximately 2600 Nile tilapia fry weighing and measuring, respectively, between 0.25-2.50g and 26-53mm, aged 35 to 60 days after hatch (DAH), were sexed using this methodology. In situ microscopic examination on the gonads was also performed. A reliable sexing using squash mount was possible with fish weighing more than 0.500g, 45-47 DAH. Results from microscopic observation using the aceto-carmine stain coincided 100% with the histological examination. Male gonadal tissue was characterized by the presence of cysts containing spermatogonia and spermatocytes, while females were easily identified by the presence of oocytes at the perinucleolar stage. The technique proved to be efficient not only in terms of evaluating sex proportion in fish but also because it allows immediate evaluation of gonadal sex and demands less time and labour.

New and improved molecular sexing methods for museum bird specimens

We present two new avian molecular sexing techniques for nonpasserine and passerine birds (Neognathae), which are more suitable for use with museum specimens than earlier methods. The technique for nonpasserines is based on a new primer (M5) which, in combination with the existing P8 primer, targets a smaller amplicon in the CHD1 sex-linked gene than previously. Primers targeting ATP5A1, an avian sex-linked gene not previously used for sex identification, were developed for passerines. Comprehensive testing across species demonstrated that both primer pairs sex a range of different species within their respective taxonomic groups. Rigorous evaluation of each method within species showed that these permitted sexing of specimens dating from the 1850s. For corn bunting museum specimens, the ATP5A1 method sexed 98% of 63 samples (1857–1966). The M5/P8 CHD1 method was similarly successful, sexing 90% of 384 moorhen specimens from six different museum collections (1855–2001). In contrast, the original P2/P8 CHD1 sexing method only identified the sex of less than half of 111 museum moorhen samples. In addition to dried skin samples, these methods may be useful for other types of material that yield degraded or damaged DNA, and are hence potential new sexing tools for avian conservation genetics, population management and wildlife forensics.

Molecular determination of sex-ratio in Yellowhammer Emberiza citrinella offspring

Theory predicts skewed offspring sex-ratios in a range of situations in which the economics of producing the two sexes differ. Offspring sex-ratio skews in birds are relatively scarcely observed compared to other taxa. This could be because avian molecular sexing techniques, which allow young birds to be sexed, have only recently become available. Alternatively, birds may be largely constrained from adaptively manipulating the sex-ratio of their offspring. We used a recently-developed molecular sexing technique for birds to sex 420 Yellowhammer Emberiza citrinella offspring from 168 clutches found in Oxfordshire. Clutch sex-ratio of the population did not depart from the expected binomial distribution, and there was no variation in clutch sex-ratio with laying date, breeding attempt, or a variety of habitat variables which were predicted to differentially affect the survival and future reproductive success of offspring of the two sexes. There was no difference in size or growth rate of the sexes and nestling mortality was not sex-biased. Hence, although we can identify possible advantages of manipulating the sex-ratio in this species, it seems not to be used as a breeding strategy. Given the lack of consistent evidence for skewed avian offspring sex-ratios, more experimental work is required to determine whether, and how, birds may adaptively manipulate their offspring sex-ratio.

The expression of pre- and postcopulatory sexually selected traits reflects levels of dietary stress in guppies

Environmental and ecological conditions can shape the evolution of life history traits in many animals. Among such factors, food or nutrition availability can play an important evolutionary role in moderating an animal's life history traits, particularly sexually selected traits. Here, we test whether diet quantity and/or composition in the form of omega-3 long chain polyunsaturated fatty acids (here termed 'n3LC') influence the expression of pre- and postcopulatory traits in the guppy (Poecilia reticulata), a livebearing poeciliid fish. We assigned males haphazardly to one of two experimental diets supplemented with n3LC, and each of these diet treatments was further divided into two diet 'quantity' treatments. Our experimental design therefore explored the main and interacting effects of two factors (n3LC content and diet quantity) on the expression of precopulatory (sexual behaviour and sexual ornamentation, including the size, number and spectral properties of colour spots) and postcopulatory (the velocity, viability, number and length of sperm) sexually selected traits. Our study revealed that diet quantity had significant effects on most of the pre- and postcopulatory traits, while n3LC manipulation had a significant effect on sperm traits and in particular on sperm viability. Our analyses also revealed interacting effects of diet quantity and n3LC levels on courtship displays, and the area of orange and iridescent colour spots in the males' colour patterns. We also confirmed that our dietary manipulations of n3LC resulted in the differential uptake of n3LC in body and testes tissues in the different n3LC groups. This study reveals the effects of diet quantity and n3LC on behavioural, ornamental and ejaculate traits in P. reticulata and underscores the likely role that diet plays in maintaining the high variability in these condition-dependent sexual traits.

Can international human rights law accommodate bodily diversity?

This article considers recent efforts by international bodies and advocacy groups to secure the human rights of individuals with intersex variation. Identifying that these efforts are constrained by powerful assumptions about binary sex, it argues that international rights discourse looks set to regulate intersex individuals by the same protective strategies applied to the last four decades of the women's rights movement. A frank reading of legal feminist scholarship indicates several possible risks for the nascent intersex campaign. Efforts to ensure the substantive enjoyment of rights (for all) need to move beyond the constraints of a binary system in which women and sexed/sexual minorities will always be produced as other. Having argued that human rights are not contingent on biological determinants, the right to non-discrimination on the basis of sex traits is considered.