Infraspecific categories in birds

The systematics of birds has probably received more attention than that of any other animal group. However, a reassessment of many species, from the point of view of their evolution, would prove valuable both from the point of view of their systematics, and the part played by various populations in speciation.
The development of evolutionary biology has resulted in a better understanding of such concepts as geographical isolation and clinal variation, a different interpretation of such terms as 'deme' and 'race', and the rejection of such all-embracing terms as 'variety'. The concept of the 'ecotype' plays little part in the systematics of birds, since they are warm-blooded, and independent of direct environmental effects.     

TRENDS IN AVIAN SYSTEMATICS

The classical "new systematics" with its replacement of the monotypic by the polytypic species, and of the morphological by the biological species concept, is now so universally accepted in ornithology that it can hardly be considered any longer as "new". Present trends indicate two areas of avian systematics favourable for active expansion, population systematics and phylogenetic systematics. Instead of describing the population structure of species in terms of subspecies, the trend will be to describe it in terms of "geographical isolates", "population continuats", and "zones of secondary intergradation" of former geographic isolates. Such an analysis can shed much light on the ecological requirements of species and on their former history. The other area of new avian systematics is a re-activated study of the higher categories of birds, with new methods and interpreted by a re-evaluated set of phylogenetic and evolutionary concepts.     

Avian Jaw Function: Adaptation of the Seven–Muscle System and a Review

Avian jaw function is the most interesting part of the feeding apparatus, and essential in the life of birds. The usual seven jaw muscles in birds are highly adapted for diverse food-getting devices through muscular modifications as well as changes in kinesis of the skeletal components of the skull. In the first part I have described from an introspection of my earlier works, the functional morphology of the seven jaw muscles in different birds in four functional groups such as, adductors of the lower jaw, depressor of the lower jaw, protractors of the upper jaw and retractors-cum-adductors of the upper and lower jaws. Emphasis has been laid on the differential force production by these muscles, depending on the nature of their connective tissue attachments on the skeletal parts and changes in the kinesis of the skeletal parts. The contraction of the muscles and movements of the skeletal parts are rhythmically synchronized in such a way that their concerted action performs adaptively in different feeding adaptations. The differential force production by the one-joint and two-joint muscles in terms of ‘torque’ analysis is important in jaw kinesis. The second part of the text is a historical review of some notable works centred around the avian jaw muscles, jaw kinesis, tongue muscles, synchronization with the movements of the tongue apparatus and adaptational as well as evolutionary significance of the feeding apparatus in different feeding strategies.     

Sexual selection and tail streamers in the barn swallow

The functional significance of elongated, narrow tips of the tail feathers of certain birds, so-called tail streamers, has recently been discussed from an aerodynamic point of view, and the effects of sexual selection on such traits have been questioned. We review our long-term field studies using observational and experimental approaches to investigate natural and sexual selection in the barn swallow, Hirundo rustica, which has sexually size-dimorphic outermost tail feathers. Experimental manipulation of the length of the outermost tail feathers has demonstrated sexual selection advantages of tail elongation and disadvantages of tail shortening, with opposite effects for natural selection in terms of foraging efficiency, haematocrit and survival. These findings are contrary to the prediction of a general deterioration from both shortening and elongation, if the tail trait was determined solely by its effects on aerodynamic efficiency and flight manoeuvrability. Patterns of sexual selection in manipulated birds conform with patterns in unmanipulated birds, and selection differentials for different components of sexual selection in manipulated birds are strongly positively correlated with differentials in unmanipulated birds. Age and sex differences in tail length, and geographical patterns of sexual size dimorphism, are also consistent with sexual selection theory, but inconsistent with a purely natural selection advantage of long outermost tail feathers in male barn swallows.     

Characteristics of the distribution of birds infected with hemosporidians (Sporozoa, Haemosporidia) during the fall migration in flight waves

Chaffinches, infected with hemoproteids (Haemoproteidae) and leucocytozoids (Leucocytozoidae), are uniformly distributed in the ranges of each nonequivalent from the point of view of bioenergetics migratory wave. Extensiveness of infection of birds with leucocytozoids in autumn increases reliably at the time of late migratory waves as compared to early ones. The last flight wave, which is observed in the Kurskaya Kosa in the second half of October, consists, in general, of chaffinches which have already gone through the leucocytozoonosis. Concentration of infected birds at the end of the species migration flow can be regarded as a peculiar parasitic filter delaying the birds, which have been seriously ill, from flying away to wintering places at the most favourable periods. The thesis on different influence of hemosporidians on energetic balance of birds during spring and autumn migrations is substantiated. Hypothesis has been advanced on the causal relationship between high bird mortality during spring migration and the most high extensiveness and intensity of their infection with hemosporidians.     

Biogeography and ecology: towards the integration of two disciplines

Although ecology and biogeography had common origins in the natural history of the nineteenth century, they diverged substantially during the early twentieth century as ecology became increasingly hypothesis-driven and experimental. This mechanistic focus narrowed ecology''s purview to local scales of time and space, and mostly excluded large-scale phenomena and historical explanations. In parallel, biogeography became more analytical with the acceptance of plate tectonics and the development of phylogenetic systematics, and began to pay more attention to ecological factors that influence large-scale distributions. This trend towards unification exposed problems with terms such as ‘community’ and ‘niche,’ in part because ecologists began to view ecological communities as open systems within the contexts of history and geography. The papers in this issue represent biogeographic and ecological perspectives and address the general themes of (i) the niche, (ii) comparative ecology and macroecology, (iii) community assembly, and (iv) diversity. The integration of ecology and biogeography clearly is a natural undertaking that is based on evolutionary biology, has developed its own momentum, and which promises novel, synthetic approaches to investigating ecological systems and their variation over the surface of the Earth. We offer suggestions on future research directions at the intersection of biogeography and ecology.     

NOTES ON THE BIOLOGY AND ETHOLOGY OF THE NATAL ROBIN COSSYPHA NATALENSIS

A preference for bushy evergreen undergrowth determines both the local and the general distribution of Cossypha natalensis. The lack of such undergrowth makes equatorial rain-forests unsuitable. Tropical and subtropical evergreen forests provide excellent conditions from this point of view, and they are thus the main habitat type from which C. natalensis has secondarily extended into tropical and subtropical deciduous forests with evergreen undergrowth.
Adult birds remain in or close to their territories throughout the year. First-year birds undertake longer movements during the winter. Breeding territories are relatively small, from 2,500 up to (exceptionally) 10,000 square yards (2,100-8,400 sq. m).
Breeding begins in October. Both sexes build the nest, but only the female incubates. In southern Africa there is one brood a year, and the care of the offspring is protracted. The juvenile moult begins in the third and ends in the sixth month; adults have only one (post-breeding) moult a year.
The begging behaviour of the young is somewhat different from that of most other turdine birds, and is considered to be more primitive. The ontogeny of the adult displays is described as observed in young birds kept in captivity.
The development of vocal behaviour is described. Special attention is given to the different functional forms of the song, and to two of its special features, imitation and a tonal quality termed vox humana.     

STRUCTURE, COMPOSITION AND BIOGENESIS OF PRASINOPHYTE SCALES

The species composition of phytoflagellates in the Salton Sea has recently been the subject of intense investigation as part of an analysis of the Salton Sea ecosystem. The Salton Sea, an inland sea occupying 980 km² in southern California, has become a major stopping point for migratory birds along the Pacific Flyway. The increasing salinity of the sea, currently at 44 gm L⁻¹, and its eutrophic condition (average depth is nine meters, with a high nutrient load contributed by agricultural drainage from the surrounding farmlands) have contributed to a stressed ecosystem. Massive fish kills and bird kills, including such endangered birds as the brown pelican, have become a recurring problem. Although previous investigations have noted the presence of at least two phytoflagellates implicated in fish mortality, little attention has been paid the to the identities of the smaller flagellates observed growing in the sea and their possible contribution to the fish and bird population mortality. Using freshly collected field samples as well as enrichment culture techniques, we report the occurrence of several genera of cryptomonads in the Salton Sea, including representatives from the genera Chroomonas , Hemiselmis , Leucocryptos , Plagioselmis , Storeatula and Teleaulax.     

Evolution and systematic relationships in theTriticeae (Poaceae)

The evolution and taxonomic relationships in theTriticeae are discussed with the view to highlight aspects of this agronomically important group of plants, which may be of interest to molecular biology. Some of these aspects are addressed in more detail in adjoining papers in which specific genomic loci have been examined at the DNA sequence or isozyme level. Aspects discussed include the systematics and geographic distribution of theTriticeae species, isozyme and chromosome pairing studies on some of the species as well as more recent developments in DNA analyses. A survey of the systematics of theTriticeae indicated that the genomic system ofLöve is probably the most useful starting point for interpreting molecular data even though the system has many problems from a taxonomic point of view. The geographical distribution ofTriticeae species, using both published and unpublished data, suggested that information of this type taken together with the theory of continental drift provides a broad time-span for considering data from DNA sequence studies. The significance, and modes of analyses, of isozyme studies were assessed because they often provide valuable characters in determining relationships between species. The main character underlyingLöve's andDewey's analyses of theTriticeae, namely chromosome pairing, is discussed with particular reference to isozyme studies to show that in some cases, such as species ofHordeum sensu lato, consistent relationships are obtained. Finally, new developments in understanding chromosome structure are considered in relation to the above variables in the taxonomy and evolution of theTriticeae.     

Spina cortica and Tapetum spinosus, two new microstructures of flight feathers: description, function and distribution in modern birds

The importance of feathers for the avian group has made them one of the most studied epidermal structures both from the morphological and evolutionary point of view. Surprisingly, our observations by Scanning Electron Microscopy detected the presence of two structures widely distributed within different avian groups and not yet described. In this paper we describe these two new structures (Spina cortica and Tapetum spinosus) and map their distribution within modern birds. The S. cortica is a thorn-like microstructure that grows on the barb cortex and the T. spinosus is the assemblage of these thorns. The distribution of these new structures among birds and their morphological diversity could be of great interest to taxonomists and evolutionary biologists interested in the origin of bird flight.     

Modelling Disease Introduction as Biological Control of Invasive Predators to Preserve Endangered Prey

Invasive species are a significant cause of bio-diversity loss particularly in island ecosystems. It has been suggested to release pathogenic parasites as an efficient control measure of these mostly immune-naïve populations. In order to explore the potential impacts of such bio-control approach, we construct and investigate mathematical models describing disease dynamics in a host population that acts as a predator embedded in a simple food chain. The consequences of Feline Immunodeficiency Virus (FIV) introduction into a closed ecosystem are addressed using a bi-trophic system, comprising an indigenous prey (birds) and an introduced predator (cats). Our results show that FIV is unlikely to fully eradicate cats on sub-Antarctic islands, but it can be efficient in depressing their population size, allowing for the recovery of the endangered prey. Depending on the ecological setting and disease transmission mode (we consider proportionate mixing as well as mass action), successful pathogen invasion can induce population oscillations that are not possible in the disease-free predator–prey system. These fluctuations can be seen as a mixed blessing from a management point of view. On the one hand, they may increase the extinction risk of the birds. On the other hand, they provide an opportunity to eradicate cats more easily in combination with other methods such as trapping or culling.     

From types to individuals: Hennig’s ontology and the development of phylogenetic systematics

Contemporary phylogenetic systematics was framed, in part, as a response to a resurgent idealistic morphology in the German‐speaking world in the first half of the 20th century. There were also conceptual and methodological challenges from Anglo‐American researchers who were sceptical about whether a phylogenetic approach to systematics could be made to work. This paper describes these challenges as a way of providing context for some ontological innovations made first by Walter Zimmermann and then by Willi Hennig. The principal argument of this paper is that what has become known as the individuality thesis played a much more important role in the conceptual foundations of Hennig’s version of phylogenetic systematics than has been widely appreciated. Understanding Hennig’s ontology illuminates his responses to objections to phylogenetic systematics from both sides of the Atlantic and sheds substantial light on the extinction part of the dichotomy rule. Although many have taken Hennig’s claim that parent species go extinct at speciation to be an arbitrary and biologically unrealistic rule, extinction of the parent follows directly from the way Hennig understands species and how they are individuated. © The Willi Hennig Society 2011.     

SHORT NOTES

Bock, W. 2000. Heuristics in systematics. Ostrich 71 (1 &; 2): 41–44.

Avian systematics is not only part of the science of ornithology, but serves heuristically as a foundation for many other analyses in ornithology. Systematics can be divided roughly into two major areas, namely species-level analyses and supraspecific classification. Of greatest significance is the distinction between provisional classifications and standard sequences, the latter are based on widely accepted classifications and have major useful functions such as the arrangement of taxa in handbooks, check-lists, and museum collections. The species concept is part of evolutionary theory, not systematics, and applies to contemporaneous groups of individual organisms. Clear distinctions separate the species concept, the species category, the species taxon, and the phyletic lineage—all usually designated as the “species”. The frequent practice of recognising all distinctive allopatric forms as separate species taxa results in two discrete classes of species taxa which largely destroys their usefulness for other biological analyses, including conservation efforts.     

Aphyly: identifying the flotsam and jetsam of systematics

Many taxon names in any classification will be composed of taxa that have yet to be demonstrated as monophyletic, that is, characterized by synapomorphies. Such taxa might be called aphyletic, the flotsam and jetsam in systematics, simply meaning they require taxonomic revision. The term aphyly is, however, the same as, if not identical to, Hennig's “Restkörper” and Bernardi's merophyly. None of these terms gained common usage. We outline Hennig's use of “Restkörper” and Bernardi's use of merophyly and compare it to aphyly. In our view, application of aphyly would avoid the oft made assumption that when a monophyletic group is discovered from within an already known and named taxon, then the species left behind are rendered paraphyletic. By identifying the flotsam and jetsam in systematics, we can focus on taxa in need of attention and avoid making phylogenetic faux pas with respect to their phylogenetic status.     

Evolutionary trends in wading birds

For the most part populations ot wading birds have expanded and contracted with the variations in the extent of their habitats during the Pleistocene. It is suggested that as a result of geographical isolation, populations of the same species have evolved to a level at which secondary hybridization has resulted on their again coming together. 'Southern' forms of some wading birds have resulted from this secondary hybridization and in some cases the increased heterogeneity has given rise to new evolutionary potential. It is suggested that this may have occurred many times during the Pleistocene and that microevolution has played a significant part in the evolution of wading birds.     

A genomic schism in birds revealed by phylogenetic analysis of DNA strings

The molecular systematics of vertebrates has been based entirely on alignments of primary structures of macromolecules; however, higher order features of DNA sequences not used in traditional studies also contain valuable phylogenetic information. Recent molecular data sets conflict over the phylogenetic placement of flightless birds (ratites - paleognaths), but placement of this clade critically influences interpretation of character change in birds. To help resolve this issue, we applied a new bioinformatics approach to the largest molecular data set currently available. We distilled nearly one megabase (1 million base pairs) of heterogeneous avian genomic DNA from 20 birds and an alligator into genomic signatures, defined as the complete set of frequencies of short sequence motifs (strings), thereby providing a way to directly compare higher order features of nonhomologous DNA sequences. Phylogenetic analysis and principal component analysis of the signatures strongly support the traditional hypothesis of basal ratites and monophyly of the nonratite birds (neognaths) and imply that ratite genomes are linguistically primitive within birds, despite their base compositional similarity to neognath genomes. Our analyses show further that the phylogenetic signal of genomic signatures are strongest among deep splits within vertebrates. Despite clear problems with phylogenetic analysis of genomic signatures, our study raises intriguing issues about the biological and genomic differences that fundamentally differentiate paleognaths and neognaths.     

Prolactin and helping in birds: has natural selection strengthened helping behavior?

The evolution of helping behavior in birds has been hotly debated.Hamilton's inclusive fitness theory has received much supportfrom ecological cost-benefit studies; however, the hypothesisthat helping has not been selected per se but is simply a phenotypicallyplastic response to altered social conditions has been proposed.In this view helping by nonbreeding birds occurs when at independencethey fail to leave their parents and are exposed to the criticalstimulus, the begging of young birds to be fed. We report thatlevels of prolactin, a hormone associated with parental behavior,are conspicuously higher in an avian species with helpers, theMexican jay (Aphelocoma ultramarina), than in a congeneric andsympatric species without helpers, the western scrub jay (A.californica). Specifically, prolactin in the nonbreeding membersof the helping species is higher than the level found in thebreeders of the congeneric nonhelping species. In addition,prolactin levels in nonbreeders rise well before the appearanceof begging young. These findings reject the phenotypic plasticityhypothesis based purely on a response to begging young and suggestthat prolactin is involved in the physiology of helping behaviorin birds as part of a complex adaptation.     

Functional linkages for the pace of life, life-history, and environment in birds

For vertebrates, body mass underlies much of the variation in metabolism, but among animals of the same body mass, metabolism varies six-fold. Understanding how natural selection can influence variation in metabolism remains a central focus of Physiological Ecologists. Life-history theory postulates that many physiological traits, such as metabolism, may be understood in terms of key maturational and reproductive characteristics over an organism's life-span. Although it is widely acknowledged that physiological processes serve as a foundation for life-history trade-offs, the physiological mechanisms that underlie the diversification of life-histories remain elusive. Data show that tropical birds have a reduced basal metabolism (BMR), field metabolic rate, and peak metabolic rate compared with temperate counterparts, results consistent with the idea that a low mortality, and therefore increased longevity, and low productivity is associated with low mass-specific metabolic rate. Mass-adjusted BMR of tropical and temperate birds was associated with survival rate, in accordance with the view that animals with a slow pace of life tend to have increased life spans. To understand the mechanisms responsible for a reduced rate of metabolism in tropical birds compared with temperate species, we summarized an unpublished study, based on data from the literature, on organ masses for both groups. Tropical birds had smaller hearts, kidneys, livers, and pectoral muscles than did temperate species of the same body size, but they had a relatively larger skeletal mass. Direct measurements of organ masses for tropical and temperate birds showed that the heart, kidneys, and lungs were significantly smaller in tropical birds, although sample sizes were small. Also from an ongoing study, we summarized results to date on connections between whole-organism metabolism in tropical and temperate birds and attributes of their dermal fibroblasts grown in cell culture. Cells derived from tropical birds had a slower rate of growth, consistent with the hypothesis that these cells have a slower metabolism. We found that dermal fibroblasts from tropical birds resisted chemical agents that induce oxidative and non-oxidative stress better than do cells from temperate species, consistent with the hypothesis that birds that live longer invest more in self-maintenance such as antioxidant properties of cells.     

Movements of radio-tagged Grey Herons Ardea cinerea during the breeding season in a large pond area

This paper describes the strategies of resource utilization in the course of the breeding season by five radio-tagged Grey Herons Ardea cinerea. The seasonal changes in exploitation of the environment by two breeding adults, one non-breeding adult and two non-breeding first-year birds were studied from March to August 1982, near Zonhoven in Belgium. Two adult breeding birds could be followed continuously from the end of March until the middle of June. During the first month they explored an extended area all around the colony, but each concentrated its search in a specific direction. From the end of April until the beginning of June, most probably from egg-hatching until the end of breeding activities, each bird spent a very large proportion of its time at a particular feeding site, from which other herons were actively excluded. In the first part of June they again visited different sites, each maintaining its preferred direction. From the middle of June onwards they seemed to have left the fish-pond area. The pattern of movements of the first-year birds differed markedly from that of the breeding adults. In April, although both non-breeding and breeding birds explored large areas, only the areas used by non-breeders were centred on the colony. From the end of April onwards, probably after general egg-hatching in the colony, the non-breeders very rarely revisited the colony, and from May till August their ranges became more and more restricted to very small areas at an increasing distance from the colony. They were never observed defending particular sites. The results are discussed with regard to recent speculations about the evolution of colonies as an adaptation for the exploitation of food resources. Breeding herons seem to explore a large part of the environment during incubation and defend a particular site while feeding their young. Choice of feeding site by non-breeding birds may be influenced by the site defence of the breeding birds. Non-breeding birds exploit a large area when breeding birds occupy feeding territories. Perhaps they are forced to forage in less suitable places at this time. Colonies might have evolved as a strategy to minimize effort in resource esploitation as, especially at the beginning of the breeding season, the colony could act as an assembly point in the exploration of the environment. However, its importance as an assembly point diminishes in the course of the season, as non-breeding birds no longer visit the colony and adults defend territories.