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Casey Albert Wood’s The fundus oculi of birds, published in 1917, was the culmination of his decade-long study of the eyes of about a hundred bird species across the avian phylogeny. Wood was a professional ophthalmologist who, during his spare time, was drawn to the study of birds’ eyes because of their exceptional visual acuity. His stated goal was to inform taxonomy but that turned out to be pointless. With the assistance of an artist, Arthur William Head, Wood described and illustrated in colour the retina in these birds, with particular attention to the number, size, structure, and position of the pecten. Since the function and evolution of the avian pecten is still poorly known, Wood’s book continues to provide a useful point of departure for the study of birds’ eyes.

We studied the shapes of eggs from 955 extant bird species across the avian phylogeny, including 39 of 40 orders and 78% of 249 families. We show that the elongation component of egg shape (length relative to width) is largely the result of constraints imposed by the female's anatomy during egg formation, whereas asymmetry (pointedness) is mainly an adaptation to conditions during the incubation period. Thus, egg elongation is associated with the size of the egg in relation to both the size of the female's oviduct and her general body conformation and mode of locomotion correlated with pelvis shape. Egg asymmetry is related mainly to clutch size and the structure of the incubation site, factors that influence thermal efficiency during incubation and the risk of breakage. Importantly, general patterns across the avian phylogeny do not always reflect the trends within lower taxonomic levels. We argue that the analysis of avian egg shape is most profitably conducted within taxa where all species share similar life histories and ecologies, as there is no single factor that influences egg shape in the same way in all bird species.

Since the late 1600s it has been assumed that the Great Auk Pinguinus impennis was similar to the Common Guillemot Uria aalge and Brünnich’s Guillemot U. lomvia in having a single, central brood patch. Through the examination of eight mounted museum specimens, we show that this is incorrect and that like its closest relative the Razorbill Alca torda, the Great Auk had two lateral brood patches. We discuss how such misinformation persisted for so long. We also review the relationship between the number of brood patches and clutch size in the Alcidae. One implication of two brood patches is that the Great Auk would have incubated in a horizontal posture like the Razorbill, rather than in a semi-upright posture like the Uria guillemots. Assuming that the Great Auk incubated like the Razorbill, it would probably have done so horizontally with its single egg pressed against one of the two lateral brood patches, positioned against the inside of one tarsus (and partially on the web of one foot), and with the wing on that side drooped to provide additional protection for the egg. Incubating in this way may have meant that the Great Auk’s pyriform egg would have enabled it to use both level and sloping terrain, as in the Uria guillemots (but unlike the Razorbill). A horizontal incubation also has implications for estimates of their breeding density, which we estimate to have been around four pairs per square meter and, hence numbers on its largest known colony, Funk Island, Newfoundland (maximum 250,000 pairs).

The Taylor White Collection of paintings from the 1700s, held at the McGill University Library, includes 661 paintings that illustrate 832 birds from around the world. With illustrations of 443 species in 30 avian orders, this collection represents a substantial proportion of the bird species known at the time and is one of the most comprehensive and accurate collections of coloured bird illustrations made during the eighteenth century. Most of the paintings were made by Charles Collins and Peter Paillou from live birds or dead specimens in the cabinets and aviaries of White and his contemporaries. We compared a large sample of the paintings with the same birds depicted in modern bird guides to assess quantitatively the accuracy of the illustrations with respect to the colours and patterns of plumages and soft parts. We found that fewer than 3% of the paintings contained errors, and usually only in one of the 28 body regions that we assessed. Given this high level of accuracy, we identified a small red macaw from the West Indies as likely representing a previously unknown but now extinct subspecies of the Scarlet Macaw, and two other paintings of species that could not be convincingly matched to any known species.

Nearly 70 years ago, Preston published a pioneering study in which he provided formulae for the shapes of birds’ eggs. One of these formulae is universal in that it provides an almost perfect representation for all eggs, even pyriform ones, and is better than all other formulae published since. This essentially perfect representation of egg shape is obtained by estimating the parameters in Preston’s universal formula by least squares, using hundreds of measurements of the egg’s radii along its entire length. Preston’s universal formula can also be used to obtain an equation for avian egg shape that uses just 5 measurements (the length and 4 appropriately spaced diameters). The equation based solely on these 5 measurements provides an egg shape that is virtually indistinguishable from one based on hundreds of measurements. We demonstrate the usefulness of Preston’s formulations using digital photographs of eggs. Our perspective is that, despite a number of subsequent approaches, Preston’s original one has not been bettered and should be the standard for studying avian egg shape.

Both sexes of Whiskered Auklets (Aethia pygmaea) display the most elaborate feather ornaments of any seabird: a slender black forehead crest, and 3 bilaterally symmetrical pairs of white facial plumes (superorbital, suborbital, and auricular). We studied patterns of ornament variation in 796 banded individuals (147 of known sex, 254 of known age from 1 to 16 years) during 1992–2009 at Buldir Island (principally), and 3 other Aleutian Islands (Davidof, Ulak, and Egg) in Alaska, USA. As expected for socially selected traits, ornaments were more variable across individuals than anatomical traits in size but with only slightly male-biased sexual dimorphism. Body condition index increased from age 1 to 3 years but changed little thereafter. Even within birds ≥4 years old, ornament size was positively related to body condition index. Subadults (one-year-olds) had smaller ornaments than adults (age 2–16 years) but there was no further change in ornament size as adults aged and no evidence of senescence even in the oldest birds (>8 years old). Nonetheless, overall ornament size varied from year-to-year at Buldir and was correlated with indices of both ocean climate and auklet productivity in the preceding 2–5 years. From Buldir to Egg Island (1,266 km), the size of both anatomical and ornamental traits increased by 5–15% except for bill depth, which was largest in birds from Buldir and Egg at opposite ends of the Aleutian breeding range. This study is one of few to examine patterns of ornament variation in a long-lived, socially monogamous bird, even though such patterns are crucial to understanding the relationship between sexual selection and life history.

We studied the ground colors and maculations of 161 Common Murre (Uria aalge) eggs laid by 43 females in 3 small breeding groups on the cliffs of Skomer Island, Wales, in 2016–2018. Both the colors and maculations varied much more among than within females, providing quantitative evidence for the egg traits that might facilitate the parents' ability to identify their own eggs on the crowded breeding ledges where the density is typically ∼20 eggs m–2. Ground colors had a trimodal distribution of hue values (whitish to pale brown, pale blue, or vivid blue-green) and maculations ranged from none to complex squiggles and blotches. The eggs laid by each female in different years were similar to one another, and replacement eggs laid by females within years were also more similar to their first egg than to other eggs in the same breeding group. Egg appearance did not differ among the 3 breeding groups that we studied. Our findings thus support anecdotal observations that, within and between years, female Common Murres lay eggs that have similar ground colors and maculations. We do not, however, find evidence that there is much difference among the eggs laid in different parts of a colony. LAY SUMMARY For more than a century, naturalists have marveled at the diversity of colors and markings on the eggs of Common Murres (Uria aalge) breeding in dense coastal colonies, where they lay and incubate a single egg. Largely anecdotal observations have suggested that each female lays distinctive eggs, and that eggs laid on the same cliff ledge tend to be more similar than expected if pairs are distributed randomly. We measured the appearance of 161 eggs laid by 43 Common Murres over a 3-year period on Skomer Island, Wales. Each female consistently laid eggs within a narrow range of whitish to pale brown (11 females) or pale blue to vivid blue-green ground color (32 females) and similar markings both within- and between breeding seasons. Despite offspring tending to return to breed near their parents, eggs laid within a few meters of one another were no more similar to each other than they were to eggs laid on cliff ledges 200 m away.

Life history theory predicts that females may increase reproductive allocation with advancing age as the probability for future reproduction diminishes. In iteroparous fishes, increasing age is usually accompanied by increasing fecundity but evidence of increasing offspring quality is less consistent. We examined the developmental rate and survival of walleye embryos with respect to female age, size, condition, and various ova traits in an exploited stock dominated by young spawners. Embryo batches from individual females were collected in the field on multiple dates and reared to hatch under controlled conditions in both flow-through and static incubation systems. Survival and thermal inputs to hatch (TU50) were analyzed with respect to spawn date, incubation method, and both maternal and ova traits. Spawning date had a relatively strong effect on embryo survival but only a minor effect on TU50, whereas incubation method had a small effect on survival but a stronger effect on TU50. Embryos reared in static incubators required greater thermal inputs to reach hatch. Using a model selection approach to assess the effects of maternal and ova traits, we found that neither maternal age nor size were strong predictors of survival or TU50. Instead, survival was more strongly related to egg size and fatty acid composition, and TU50 was not strongly related to any maternal or ova trait. Our results suggest that the nature and magnitude of maternal effects on early development and survival may vary among walleye stocks, modified by physical conditions during incubation.

In the three decades, since Birkhead and Møller published Sperm competition in birds (1992, Academic Press) more than 1000 papers have been published on this topic, about half of these being empirical studies focused on extrapair paternity. Both technological innovations and theory have moved the field forward by facilitating the study of both the mechanisms underlying sperm competition in both sexes, and the ensuing behavioural and morphological adaptations. The proliferation of studies has been driven partly by the diversity of both behaviours and morphologies in birds that have been influenced by sperm competition, but also by the richness of the theory developed by Geoff Parker over the past 50 years. This article is part of the theme issue ‘Fifty years of sperm competition’.

The adaptive significance of avian egg shape is a long-standing problem in biology. For many years, it was widely believed that the pyriform shape of the Common Murre (Uria aalge) egg allowed it to either “spin like a top” or “roll in an arc,” thereby reducing its risk of rolling off the breeding ledge. There is no evidence in support of either mechanism. Two recent alternative hypotheses suggest that a pyriform egg confers mechanical strength and minimizes the risk of dirt contamination of the blunt end. We present a new hypothesis: that the Common Murre egg's pyriform shape confers stability on the breeding ledge, thus reducing the chance that it will begin to roll. We tested this hypothesis by measuring the stability of Common Murre and Razorbill (Alca torda) eggs of different shapes on slopes of 20°, 30°, and 40° above the horizontal. Common Murre eggs were more stable, and easier to stabilize, than the more elliptical Razorbill eggs. Within Common Murre eggs, more pyriform eggs were more stable. From a fitness perspective, the stability of the Common Murre egg on a slope seems likely to confer an advantage and thus may be a strong force of natural selection favoring the pyriform shape.

A recent broad comparative study suggested that factors during egg formation – in particular ‘flight efficiency’, which explained only 4% of the interspecific variation – are the main forces of selection on the evolution of egg shape in birds. As an alternative, we tested whether selection during the incubation period might also influence egg shape in two taxa with a wide range of egg shapes, the alcids (Alcidae) and the penguins (Spheniscidae). To do this, we analysed data from 30 species of these two distantly related but ecologically similar bird families with egg shapes ranging from nearly spherical to the most pyriform eggs found in birds. The shape of pyriform eggs, in particular, has previously proven difficult to quantify. Using three egg‐shape indices – pointedness, polar‐asymmetry and elongation – that accurately describe the shapes of all birds’ eggs, we examined the effects of egg size, chick developmental mode, clutch size and incubation site on egg shape. Linear models that include only these factors explained 70–85% of the variation in these egg‐shape indices, with incubation site consistently explaining > 60% of the variation in shape. The five species of alcids and penguins that produce the most pyriform eggs all incubate in an upright posture on flat or sloping substrates, whereas species that incubate in a cup nest have more spherical eggs. We suggest that breeding sites and incubation posture influence the ability of parents to manipulate egg position, and thus selection acting during incubation may influence egg‐shape variation across birds as a whole.

Huge numbers of Common Guillemot (Uria aalge) eggs were harvested by local men known as “climmers” (climbers) at Bempton Cliffs, Flamborough, Yorkshire, until 1954 when egg collecting became illegal. Guillemot eggs are more variable in colour and pattern than those of any other bird. Egg collectors (oologists) particularly favoured sets of unusually coloured eggs laid by the same bird. Red guillemots eggs were extremely rare and eagerly sought. An example of one such egg known as the “Bempton Belle” was found in the collection of J. W. Goodall (active between about 1896 and 1909), and was celebrated in a poem. What was probably another red egg, known as the “Metland Egg”, was collected each year at Bempton between 1912 and 1938. The current whereabouts of the Metland eggs is unknown. We estimate that females laying red eggs occur less than once in a thousand (or ten thousand). We also speculate about the factors responsible for red eggs and why such eggs are so rare.

During the 1830s, Charles Thorold Wood jun. and his younger brother Neville Wood, published, separately, three books and a series of articles dealing with two ornithological subjects: the common and scientific names of birds, and the cataloguing of publications. Probably following William Swainson's lead, the Woods were enthusiastic about standardizing the common (English) bird names and making them logical and meaningful. They also each published an annotated bibliography of ornithological publications, notable for being among the first of such compilations, but also for the vitriol with which they criticized those – James Rennie and Hugh Strickland, in particular – whose work they did not like. In contrast, the praise they heaped on those they did approve of – William Swainson, John Latham, Robert Mudie, Prideaux John Selby, Francis Willughby and each other – was excessive. Possibly because of the tenor of their comments about other ornithologists, and the strangeness of their proposed English bird names, the Woods’ work has rarely been cited, and their new names for birds were virtually ignored from the start.

To date, the majority of authors on scientific publications have been men. While much of this gender bias can be explained by historic sexism and discrimination, there is concern that women may still be disadvantaged by the peer review process if reviewers' unconscious biases lead them to reject publications with female authors more often. One potential solution to this perceived gender bias in the reviewing process is for journals to adopt double-blind reviews whereby neither the authors nor the reviewers are aware of each other's identities and genders. To test the efficacy of double-blind reviews, we assigned gender to every authorship of every paper published in 5 different journals with different peer review processes (double-blind vs. single blind) and subject matter (birds vs. behavioral ecology) from 2010-2018 (n = 4865 papers). While female authorships comprised only 35% of the total, the double-blind journal Behavioral Ecology did not have more female authorships than its single-blind counterparts. Interestingly, the incidence of female authorship is higher at behavioral ecology journals (Behavioral Ecology and Behavioral Ecology and Sociobiology) than in the ornithology journals (Auk, Condor, Ibis), for papers on all topics as well as those on birds. These analyses suggest that double-blind review does not currently increase the incidence of female authorship in the journals studied here. We conclude, at least for these journals, that double-blind review does not benefit female authors and may, in the long run, be detrimental.

Differences in body size are widely thought to allow closely related species to coexist in sympatry, but body size also varies as an adaptive response to climate. Here, we use a sister lineage approach to test the prediction that body size differences between closely related species of birds worldwide are greater for species whose ranges are sympatric rather than allopatric. We further test if body size differences among sympatric versus allopatric species vary with geography, evolutionary distance, and environmental temperatures. We find greater differences in size among sympatric compared with allopatric lineages, but only in closely related species that live where mean annual temperatures are above 25°C. These size differences in warm environments declined with the evolutionary distance between sister lineages. In species living in cooler regions, closely related allopatric and sympatric species did not differ significantly in size, suggesting either that colder temperatures constrain the evolutionary divergence of size in sympatry, or that the biotic selective pressures favoring size differences in sympatry are weaker in colder environments. Our results are consistent with suggestions by Wallace, Darwin, and Dobzhansky that climatic selective pressures are more important in cooler environments (e.g., high elevations and latitudes) whereas biotic selective pressures dominate in warm environments (e.g., lowland tropics).

Closely related species of birds often differ markedly in their color patterns. Here we examine the influence of breeding-range overlap (breeding sympatry) on the evolution of color pattern differences in a sample of closely related bird species. We used a sister-lineage method to analyze 73 phylogenetically independent comparisons among 246 species and 39 families of birds worldwide. We found that divergence of color patterns among closely related species was greater between sympatric than between allopatric lineages, but only at intermediate levels of sympatry (50%-80% breeding-range overlap). This pattern suggests that closely related species incur costs at intermediate levels of sympatry if they exhibit similar color patterns-costs that could include hybridization, interspecific aggression, competition for signaling space, or ecological interactions that secondarily influence color patterns. The decline in color pattern divergence with further increase in sympatry suggests either the relaxation of divergent selection, increased impediment of gene flow, or an increased role for counteracting selection at higher levels of sympatry. We also found that the differences in color pattern between sympatric and allopatric sister species were greatest at lower latitudes. The global scale and broad taxonomic coverage in our study suggest that the divergence of color patterns between sympatrically breeding closely related species is widespread in birds.

The European Honey-buzzard (Pernis apivorus) was first accurately described and clearly distinguished from the Common Buzzard (Buteo buteo) by Francis Willughby and John Ray in their Ornithology, originally published in Latin in 1676. Alfred Newton's statement that Pierre Belon had described the species over a century earlier is not entirely correct, as Belon confused this honey-buzzard's features with those of the common buzzard and even appeared uncertain whether it was a separate species. One of Willughby's important contributions to ornithology was the identification and use of “characteristic marks” to distinguish and identify species, including those that distinguish the European Honey-buzzard from the Common Buzzard. Because Willughby provided the first accurate description of Pernis apivorus – and because his contribution to ornithology has never been formally recognized – we propose that the common name of the European Honey-buzzard be changed to Willughby's Buzzard.

Perchlorate (ClO4−) contamination has been reported in ground and surface waters across North America. However, few studies have examined the effects of prolonged exposure to this thyroid hormone disrupting chemical, particularly at environmentally relevant concentrations in lower vertebrates, such as amphibians. The aim of this study was to examine the effects of a yearlong chronic exposure to ClO4− in adult male and female Western clawed frogs (Silurana tropicalis). Frogs were spawned and raised from fertilized embryo until sexual maturity in potassium perchlorate (KClO4)-treated water at different concentrations (0, 20, 53, and 107 μg/L). Developmental and reproductive indices – including adult morphology, androgen plasma levels, gonadal thyroid hormone- and sex steroid-related transcript levels, and sperm motility – were evaluated in male and female adult frogs. Female growth (e.g., body mass, snout-vent length, and hind limb length) was significantly reduced following chronic exposure to environmentally relevant concentrations of KClO4 resulting in females with morphometric indices similar to those of control males – indicating potential sex-specific sensitivities to KClO4. Changes to reproductive indices (i.e., plasma androgen levels, gonadal thyroid hormone- and sex steroid-related transcript levels, and sperm motility) were also observed in both sexes and suggest that KClO4 exposure may also have indirect secondary effects on the reproductive axes in male and female adult frogs. These effects were observed at concentrations at or below those reported in surface waters contaminated with ClO4− suggesting that this contaminant may have developmental and reproductive effects post-metamorphosis in natural amphibian populations.

Gonad size and shape asymmetries are particularly common in birds. Although some obvious size and shape differences between the left and right testes in birds were first documented more than a century ago, little is known about what influences the variation across species in either the degree or the direction of these asymmetries. Here we show that a left bias in size is the most likely ancestral state in most orders and families, and that there is a weak but significant negative relation between the degree of size and shape asymmetries. In extant species, testis size and shape symmetries increase with the degree of sperm competition (relative testes mass), but those relations are significant only in those species with left bias in each of these traits. When space is particularly constrained on the left side of the body cavity due to a large gizzard (e.g. in granivores), the left testis is more elongated and the degree of size symmetry is larger. Despite significant patterns, relative testes mass and gizzard complexity together explain < 10% of the variation in testis asymmetry in species with left biases. Thus our analyses suggest that some other factor is largely responsible for the evolution of gonad asymmetry in birds: 1) that a left bias in testis size might be a correlated response to selection for a left bias in the development of a single (left) ovary in females of most bird species, and/or 2) that physiological efficiency due to the dramatic and rapid increase in testis size of most species during the breeding season might favour enlargement of one testis. Our conclusions highlight the need to rethink and improve our understanding of the physiological processes underlying the investment in gonads by male birds.

Theory holds that dishonest signaling can be stable if it is rare. We report here that some peacocks perform specialized copulation calls (hoots) when females are not present and the peacocks are clearly not attempting to copulate. Because these solo hoots are almost always given out of view of females, they may be dishonest signals of male mating attempts. These dishonest calls are surprisingly common, making up about a third of all hoot calls in our study populations. Females are more likely to visit males after they give a solo hoot call, and we confirm using a playback experiment that females are attracted to the sound of the hoot. Our findings suggest that both sexes use the hoot call tactically: females to locate potential mates and males to attract female visitors. We suggest that the solo hoot may be a deceptive signal that is acquired and maintained through reward-based learning.

Each of the multicolored eyespots (ocelli) on the peacock’s (Pavo cristatus) train is a complex structure with a purple-black center surrounded by concentric blue-green and bronze-gold regions. To investigate the influence of all 3 of these colors on male mating success, we used a physiological model of peafowl vision to quantify those colors as females would perceive them during male courtship displays. Males display at about 45° to the right of the sun’s azimuth (on average) with the female directly in front, so we investigated how colors would be perceived when illuminated at 30°, 45°, and 60° to the right of a female observer. We studied 34 males displaying at leks in 3 feral populations and quantified their copulation success and the colors of their eyespots. Eyespot coloration explained half of the observed variation in peacock mating success, with the hue and iridescence of the blue-green patch being the most important color variables. When we experimentally masked ocelli on 9 males, their copulation success declined almost to 0, supporting the idea that the eyespots are a major focus of female attention and not a trait that is simply correlated with something else that influences female choice. Thus, our study shows that the blue-green eyespot color overwhelmingly influences peacock mating success. The influence of the other eyespot colors on male success is minimal at best, raising questions about their function.

Social selection influences the evolution of weapons, ornaments and behaviour in both males and females. Thus, social interactions in both sexual and non-sexual contexts can have a powerful influence on the evolution of traits that would otherwise appear to be detrimental to survival. Although clearly outlined by West-Eberhard in the early 1980s, the idea that social selection is a comprehensive framework for the study of ornaments and weapons has largely been ignored. In West-Eberhard's view, sexual selection is a form of social selection—a concept supported by several lines of evidence. Darwin's distinction between natural and sexual selection has been useful, but recent confusion about the limits of sexual selection suggests that some traits are not easily categorized as naturally or sexually selected. Because social selection theory has much to offer the current debates about both sexual selection and reproductive competition in females, it is sometimes viewed, narrowly, to be most useful when considering female roles. However, social selection theory encompasses much more than female reproductive competition. Our goal here was to provide that broader perspective.

Recent studies have reported conflicting evidence for the influence of train-feather eyespots on the mating success of peacocks, Pavo cristatus. In this study we address this controversy, using observation and experiment to evaluate the effect of train morphology and the number of eyespots displayed during courtship on female choice. We show first that the maximum number of eyespots in the train is consistent among adult peacocks in feral populations at about 165-170 eyespots, and that most of the observed variation in eyespot number appears to be due to feather breakage or loss. Although we confirm a previous report that removing a large number (≥20) of the outermost eyespots from a male's train decreases his mating success compared to unmanipulated males, this experimental modification produces an ornament that is outside the range of eyespot number typically displayed during courtship. Thus, the considerable variation in the mating success of feral peacocks cannot be explained by natural variation in the number of eyespots visible in the train. Peafowl mate choice is clearly more complex than previously thought: females may reject a few males with substantially reduced eyespot number, while using some other cue to choose among males with typical trains.

Certain loud calls made by female red junglefowl and Lapland longspurs are given most frequently immediately after egg laying, when a copulation should have the highest probability of fertilizing the next egg to be laid. In these species there is considerable male-male interaction for access to fertilizable females, and males are attracted to or follow females making these calls. Based on our interpretation of these calls, we develop a general hypothesis to predict the pattern of occurrence of fertility advertisement both within and among bird species. We hypothesize that certain loud calls given by female birds before and during the egg-laying period are designed to advertise fertility and thereby incite male-male competition. This hypothesis predicts that calls advertising female fertility should most often occur soon after an egg is laid (i.e. during the period of highest fertility) but may also occur at any time during the female's fertilizable period. Such calls are unlikely to be given by females in strictly monogamous species (especially those with long-term pair bonds) because in these species each female usually mates with only a single male and extra-pair copulations are avoided. Although reports of loud female calls associated with copulation are rare in the literature, the 18 examples we found (including junglefowl and longspurs) were predominantly (15/18) in species adopting mating systems other than strict monogamy, and these calls were most commonly and disproportionately reported in multi-male mating systems. This form of “estrus” in birds may be widespread because few species appear to be strictly monogamous, but it will be difficult to study because the period of high fertility for female birds is so short.

Sperm traits of externally fertilizing fish species are typically measured in fresh (or salt) water, even though the spawning environment of their ova contains ovarian fluid. In this study, we measured sperm traits of Chinook salmon ( Oncorhynchus tshawytscha (Walbaum in Artedi, 1792)) in both fresh water and dilute ovarian fluid at 10 and 20 s postactivation, using a computer-assisted sperm analysis system. Spermatozoa swam faster, and had both higher percent motility and a straighter path trajectory for a longer period of forward motility when activated in ovarian fluid compared with activation in fresh water. Comparing sperm activity of 10 males in water versus ovarian fluid, we found a weak but significant correlation for sperm swimming speed at 10 s postactivation (r = 0.34, p = 0.01), but not for any other sperm traits measured. Most important, across males, mean sperm swimming speed in water accounted for

Previous work has demonstrated that genomic incompatibilities work together with ecologically divergent selec- tion to promote and maintain reproductive isolation between incipient species (dwarf and normal) of lake whitefish (Core- gonus clupeaformis (Mitchill, 1818)). Whitefish spawn in groups with external fertilization, which creates conditions for strong sperm competition. In this study, we asked whether reduced sperm performance in hybrids from whitefish species- pair matings might contribute to postzygotic isolating mechanisms between these taxa. We examined two sperm traits, sperm swimming speed and flagellum length, in pure dwarf and normal whitefish and in their F1 and backcross hybrids. We observed significantly reduced sperm swimming speed in backcross but not in F1 hybrids. Sperm flagellum length was not significantly correlated with sperm swimming speed. These results demonstrate that F1 hybrids formed in nature should be capable of the same fertilization success as the parental species during sperm competition, everything else being equal. However, reduced sperm performance in the backcross generation is consistent with other evidence suggesting that genomic incompatibilities create a range of negative fitness effects in post-F1 whitefish hybrids and provides evidence for an additional postzygotic isolation mechanism involved in the incipient speciation of sympatric dwarf and normal white- fish. Resume´ : Des travaux anterieurs ont demontreque les incompatibilitesg enetiques agissent de concert avec la selection di- vergente en fonction de l'ecologie pour favoriser et maintenir l'isolement genetique entre les especes en emergence (naines et normales) chez les grands coregones (Coregonus clupeaformis (Mitchill, 1818)). Les coregones fraient en groupes et ont une fecondation externe, ce qui cree des conditions de forte competition spermatique. Dans notre etude, nous cherchons a savoir si la performance reduite des spermatozoo¨des des hybrides provenant de l'accouplement de paires d'especes de core ´- gones peut contribuer aux mecanismes d'isolement post-zygotique entre ces taxons. Nous examinons deux caracteristiques des spermatozoo¨des, la vitesse de nage et la longueur du flagelle des spermatozoo¨des, chez des coregones nains et normaux purs et leurs hybrides de F1 et de retrocroisement. Il y a une reduction significative de la vitesse de nage des spermato- zoo¨des chez les hybrides de retrocroisement, mais non ceux de F1. Il n'existe pas de correlation significative entre la lon- gueur du flagelle et la vitesse de nage des spermatozoo¨des. Ces resultats demontrent que les hybrides de F1 formese n nature devraient pouvoir obtenir le meme succesd e fecondation que les especes parentales durant la competition sperma- tique, toutes autres choses etant egales. Cependant, la performance reduite des spermatozoo¨des de la generation de retro- croisement est compatible avec d'autres indications qui laissent croire que les incompatibilitesg enetiques creent une gamme d'effets negatifs de fitness chez les hybrides post F1 de coregones; elle fournit aussi des preuves de l'implication d'un mecanisme additionnel d'isolement post-zygotique dans la speciation en emergence des coregones sympatriques nains et normaux. (Traduit par la Redaction)

Charles Darwin was not much of an ornithologist. Although in boyhood he spent much of his spare time hunting birds and collecting eggs, by the time he returned to England on the Beagle, at the age of 27, he was finished with studying birds in the wild. After writing up his work on the voyage of the Beagle (Darwin 1839, 1838– 1843), Darwin devoted his in-depth studies of organisms first to the barnacles (Darwin 1851), then to plants (Darwin 1862, 1875, 1876, 1880) and earthworms (Darwin 1881). Of more than 150 letters and short papers that he published, only six were about birds and none was in an ornithological journal (The Ibis began publishing, coincidentally, in 1859, and Journal fur Ornithologie in 1853). Nor was he elected to any ornithological society of the day, and his passing was not marked with an obituary in any of the ornithological journals. The names of his contemporaries John Gould and Alfred Russel Wallace figure in the presentday common names of six and nine bird species, respectively (Gill et al. 2009), whereas Darwin’s name is in only two: Darwin’s Nothura (Nothura darwinii) and Darwin’s Rhea (Rhea pennata). Ornithologists can be a cliquish lot, sometimes treating with disdain those who pursue other kinds of natural history— and, thus, are not completely devoted to the study of birds—even

We describe a unique, hand-coloured copy of Ray’s (1678) The Ornithology of Francis Willughby that was apparently presented to Samuel Pepys between 1684 and 1686 during his presidency of the Royal Society. Somehow, this volume was not catalogued as part of Pepys’s famous library, and fell into private hands until, in 1924, it was purchased for the McGill University Library in Montreal. More than 90% of the original engravings of birds in this volume are hand-coloured, making this a unique attempt to depict a large proportion of the known birds of the world in colour, and providing interesting insights into knowledge of bird colouration in the seventeenth century. The colouring of the 332 bird species on 76 hand-coloured plates is generally quite accurate—in the instances where the colouring is incorrect, it usually matches the description in Ray’s text almost exactly.

We studied two courtship displays of male peafowl (Pavo cristatus), focusing particularly on male orientation relative to the position of the sun. During the “wing-shaking” display, females were generally behind the displaying male, and male orientation with respect to the position of the sun was not significantly different from random. However, during the pre-copulatory “train-rattling” display, males were on average directed at about 45° to the right of the sun azimuth with the female positioned directly in front, suggesting that this behaviour is involved in the communication of a visual signal. A model presentation experiment confirmed that courting peacocks were more likely to perform the train-rattling display when the female was on the sunny side of their erect train, but more likely to perform wing-shaking behaviour when the female was on the shaded side of the male. This study underscores the importance of visual signalling in peafowl courtship, and we suggest that an angle of about 45° relative to the sun may allow males to enhance the appearance of their iridescent eyespot feathers.

Interest in female ornamentation has burgeoned recently, and evidence suggests that carotenoid-based female coloration may function as a mate-choice signal. However, the possibility that females may signal status with coloration has been all but ignored. Bill coloration of female American goldfinches (Spinus tristis) changes seasonally, from dull gray in winter to bright orange in the breeding season. We conducted a series of aviary experiments in the breeding season to examine the signaling role of female bill color during both intra- and intersexual contests as well as during male mate choice. We tested for status signaling by examining whether caged females and males avoided feeding adjacent to female taxidermic models as a function of the model’s bill color, which was experimentally augmented or dulled. We tested for a mate signaling function by giving captive males a choice between 2 live females with experimentally altered bill colors. Females avoided feeding near model females with colorful bills, but males showed neither avoidance of nor preference for females with more colorful bills. These results indicate that the female’s carotenoid-based bill coloration signals status during competitive interactions and suggest that female bill color does not function as a mate-choice signal. This represents the first experimental evidence that a carotenoid-based coloration of females functions to mediate contest competition over food. Key words: American goldfinch, bill color, carotenoid signal, intrasexual selection, ornamental female, social selection, Spinus (Carduelis) tristis, status signaling. [Behav Ecol]

The blood-feeding juvenile stages of gnathiid isopods are important ectoparasites of marine fishes on the Great Barrier Reef (GBR), and are a major component of the diet of cleaner fishes. We report here that these gnathiids have undergone evolutionary diversification, both geographically and temporally (into diurnally and nocturnally active taxa), which has been accompanied by changes in their morphology and behaviour. To perform this analysis, we sequenced a portion of the nuclear ribosomal ITS2 for 47 gnathiids collected from 29 host fishes of 11 species at three locales spanning 2000 km on the GBR. Maximum parsimony and Bayesian phylogenetic analyses both revealed four major clades. There was some degree of geographical structuring in these clades, but there was no evidence supporting host fish specialization, as gnathiids collected from the skin of different teleost taxa did not resolve into distinct clades. The topology of the phylogeny also implied some structuring that was dependent upon collection time (day or night), so we investigated whether there were also behavioural and morphological differences between taxa active at these different times. Nocturnal gnathiids had significantly longer antennules and larger eyes than diurnal gnathiids ‐ two traits presumably adaptive for nocturnal activity. Behavioural tests showed that both nocturnal and diurnal gnathiids use olfaction and vision while foraging, but that nocturnal gnathiids used olfaction more often in dark conditions, and that they were able to perceive movement under extremely low levels of light. Diurnal gnathiids used vision more effectively when there was some ambient light. Our results thus suggest that both phenotypic and genotypic divergence in gnathiids may be influenced by natural selection acting on ecological traits, such as predator avoidance and host detection. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 569‐587. ADDITIONAL KEYWORDS: ‐ gnathiids ‐ host specialization ‐ isopods ‐ ITS2 ‐ olfaction ‐ phylogeny ‐ vision.

Theoretical models predict that individual males will increase their investment in ejaculates when there is a risk of sperm competition. Because the production of ejaculates is assumed to be energetically costly, only those males in good physical condition should be capable of producing ejaculates of high quality. We studied ejaculate investment (relative testis size, controlling for body size) as well as the size, behaviour, and energetics of spermatozoa in lake whitefish (Coregonus clupeaformis), a species in which males provide nothing but sperm to females during reproduction. Ejaculate investment was condition dependent, with males in better body condition having relatively larger testes. Sperm adenosine triphosphate (ATP) levels were unaffected by male condition alone, but increased with testis size when controlling statistically for both male size or body condition. Thus, males investing in relatively larger testes produced spermatozoa with higher energetic capacity. We also discovered testis asymmetry in this species, a phenomenon not previously reported in fishes, though widespread in other taxa. The mass of the (larger) left testis was a better predictor of sperm ATP stores than the mass of the (smaller) right testis (controlling for body size), suggesting that testis size asymmetry might be related to the production of high-quality sperm.

Theory predicts that males experiencing elevated levels of sperm competition will invest more in gonads and produce fasterswimming sperm. Although there is ample evidence in support of the first prediction, few studies have examined sperm swimming speed in relation to sperm competition. In this study, we tested these predictions from sperm competition theory by examining sperm characteristics in Telmatochromis vittatus, a small shellbrooding cichlid fish endemic to Lake Tanganyika. Males exhibit four different reproductive tactics: pirate, territorial, satellite, and sneaker. Pirate males temporarily displace all other competing males from a shell nest, whereas sneaker males always release sperm in the presence of territorial and satellite males. Due to the fact that sneakers spawn in the presence of another male, sneakers face the highest levels of sperm competition and pirates the lowest, whereas satellites and territorials experience intermediate levels. In accordance with predictions, sperm from sneakers swam faster than sperm from males adopting the other reproductive tactics, whereas sperm from pirates was slowest. Interestingly, we were unable to detect any variation in sperm tail length among these reproductive tactics. Thus, sperm competition appears to have influenced sperm energetics in this species without having any influence on sperm size.