Phylogenetic affinities and taxonomy of the Oligocene Diomedeoididae,and the basal divergences amongst extant procellariiform birds

The Palaeogene Diomedeoididae are amongst the earliest representatives of procellariiform birds (albatrosses, tubenoses, and allies). Although several fossils of these birds have been reported in the past, many details of their osteology remained unknown. Here we describe a comprehensive collection of diomedeoidid fossils from the Rupelian stratotype in Belgium, which was found more than 100 years ago. The material includes all major limb elements as well as other cranial and postcranial bones, and allows the recognition of previously unknown features of phylogenetic significance. Based on these new osteological data, diomedeoidids were for the first time subjected to a phylogenetic analysis, which resulted in a position outside a clade including Hydrobatidae (northern storm‐petrels), Pelecanoididae (diving‐petrels), and Procellariidae (fulmars, petrels, shearwaters, and allies), either as the sister taxon of Diomedeidae (albatrosses) or as that of all crown group Procellariiformes. The latter placement is better supported by the osteological evidence, and diomedeoidids lack several apomorphies of crown group Procellariiformes. Previously unrecognized derived features are reported that support a monophyletic Hydrobatidae, thus contradicting recent proposals that Oceanitinae (southern storm‐petrels) are the earliest diverging crown group Procellariiformes. The new fossils also have a bearing on the convoluted taxonomy of diomedeoidids, and Diomedeoides Fischer, 1985 is synonymized with Rupelornis van Beneden, 1871. Diomedeoides lipsiensis (Fischer, 1983) is synonymous with Rupelornis definitus (van Beneden, 1871), a species that exhibits a large size range. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 854–875.     

Dispersal and the interspecific abundance-occupancy relationship in British birds

Aim To test the prediction that deviations of species from the positive interspecific relationship between abundance and occupancy (a measure of geographical range size) are related to differences in dispersal. Location Great Britain. Methods Quantitative data on the abundances, occupancy and dispersal distances of British birds are compared using phylogenetic comparative methods. Results Measures of natal and adult dispersal distance, and the intraspecific variance in these parameters, explain little variation in occupancy in addition to that accounted for by population size. Individual dispersal variables failed to explain significant variance when added individually to a model with population size as a predictor. Migrants and species using wet habitats tend to disperse further than residents and dry habitat species. Analysing these four groups separately revealed effects of dispersal only on the occupancy attained by dry habitat species. Conclusions The only consistent predictor of occupancy in these analyses was population size.     

Area-relationships in the Neotropical lowlands: an hypothesis based on raw distributions of Passerine birds

Abstract. Using raw geographic distributions for Neotropical species and subspecies of the perching birds (Order Passeriformes), we present an hypothesis of area-relationships for twelve avian areas of endemism in the lowland Neotropics. With 1717 characters (distributions of species and subspecies) we find a single most parsimonious tree of area-relationships. This topology does not match area-relationships determined from phylogenetic studies of morphologic characters in some Neotropical birds. Analyses of data partitions representing major taxonomic subdivisions within Passerine birds provide many different hypotheses of area-relationships. These results suggest that a single set of Neotropical area-relationships is not likely. In the future, we suggest greater emphasis be placed on research to document patterns in the Neotropics, particularly phylogenetic patterns, than on speculation about what processes have been important for diversification.     

Potential decoupling of trends in distribution area and population size of species with climate change

Global climates are changing rapidly and biological responses are becoming increasingly apparent. Here, we use empirical abundance patterns across an altitudinal gradient and predicted altitudinal range shifts to estimate change in total population size relative to distribution area in response to climate warming. Adopting this approach we predict that, for nine out of 12 species of regionally endemic birds, total population size will decline more rapidly than distribution area with increasing temperature. Two species showed comparable loss and one species exhibited a slower decline in population size with change in distribution area. Population size change relative to distribution area was greatest for those species that occurred at highest density in the middle of the gradient. The disproportional loss in population size reported here suggests that extinction risk associated with climate change can be more severe than that expected from decline in distribution area alone. Therefore, if we are to make accurate predictions of the impacts of climate change on the conservation status of individual species, it is crucial that we consider the spatial patterns of abundance within the distribution and not just the overall range of the species.     

Extrinsic factors and the population sizes of threatened birds

Attempts to explain the orders-of-magnitude variation observed in animal population sizes have principally focused on intrinsic differences between the taxa compared, but with limited success: most variation remains unexplained by such studies. However, animal population sizes may also vary in response to extrinsic factors, such as the environment occupied or the influence of human activities. Here, we use new estimates of the global population sizes of threatened bird species to examine extrinsic correlates of variation in their numbers, using general linear modelling and methods to control for phylogenetic relatedness. Threatened bird population sizes varied significantly with several extrinsic factors, including altitude, biogeographical region inhabited, type of extinction threat faced, and habitat used. They also vary with geographical range size, which was included in the analysis to control for its potentially confounding effects on the results. Details of the observed relationships, which vary with analytical method, are discussed. However, apart from geographical range size, none of the extrinsic variables analysed here explain more than a small percentage of the variation in threatened bird population sizes. Thus, it seems likely that a comprehensive explanation for why some species are common while others are rare will not be dominated by a single factor.     

Interspecific abundance–occupancy relationships of British mammals and birds: is it possible to explain the residual variation?

Aim The majority of studies concerning positive interspecific abundance–occupancy relationships have used broad‐scale and microcosm data to test the occurrence and correlates of the relationship to determine which of the proposed mechanisms give rise to it. It has been argued recently that studying the residual variation about abundance–occupancy relationships is a more logical analysis and may yield faster progress in identifying the relative roles of the mechanisms. However, to date this approach has been largely unsuccessful. Here we test if fundamental species traits such as the status (native and introduced), habitat and trophic group of mammal and bird species may explain any of the residual variation about their respective abundance–occupancy relationships. Location The study used British mammal and bird species. Methods We tested if species traits explained any of the variation about abundance–occupancy relationships using linear regression techniques both treating species as independent data points for analysis and controlling for phylogenetic association. Results None of the species traits could explain any residual variation about the positive interspecific abundance–occupancy relationships of British mammals and birds. This applied both when treating species as independent data points and after controlling for phylogenetic association. Conclusions Given the lack of explanatory power of the species traits here and in other studies using this approach it seems that the variation about positive interspecific abundance–occupancy relationships is not explicable in a simple fashion. Predicting the likely influence of traits that are independent of phylogeny is also problematic. Therefore, the general utility of this approach and its future role in understanding the mechanisms causing positive interspecific abundance–occupancy relationships is doubtful.     

Population and geographic range dynamics: implications for conservation planning

Continuing downward trends in the population sizes of many species, in the conservation status of threatened species, and in the quality, extent and connectedness of habitats are of increasing concern. Identifying the attributes of declining populations will help predict how biodiversity will be impacted and guide conservation actions. However, the drivers of biodiversity declines have changed over time and average trends in abundance or distributional change hide significant variation among species. While some populations are declining rapidly, the majority remain relatively stable and others are increasing. Here we dissect out some of the changing drivers of population and geographic range change, and identify biological and geographical correlates of winners and losers in two large datasets covering local population sizes of vertebrates since 1970 and the distributions of Galliform birds over the last two centuries. We find weak evidence for ecological and biological traits being predictors of local decline in range or abundance, but stronger evidence for the role of local anthropogenic threats and environmental change. An improved understanding of the dynamics of threat processes and how they may affect different species will help to guide better conservation planning in a continuously changing world.     

Abundance,distribution and habitat characteristics of winter skate Leucoraja ocellata in the southern Gulf of St Lawrence: a population on the brink of extirpation?

Abundance indices of southern Gulf Leucoraja ocellata residing in Northumberland Strait, Canada, declined from 2001 to 2005, but increased during 2006 to 2008. Catch rates in 2009 were the lowest in the time series. The size of the area occupied in Northumberland Strait varied with changes in the abundance indices. Leucoraja ocellata were primarily caught in the north‐west half of the strait over sandy to gravelly seabed; a near total absence was documented from the eastern half despite suitable habitat and a previously established presence documented during research surveys conducted before 2000. In Northumberland Strait, L. ocellata occupied shallow (50% cumulative occurrence = 12 m) and warm (50% cumulative occurrence = 16·5° C) coastal waters and were not present in the cold (<1° C, >35 m) intermediate layer. Abundance and distribution data highlight the need for continuing studies to monitor the status of this population, which is classified as endangered by the IUCN and Committee on the Status of Endangered Wildlife in Canada.     

A wide-range survey of cross-species microsatellite amplification in birds

The possibility to perform cross-species microsatellite amplification in birds was surveyed by analysing sets of primers developed from the swallow and the pied flycatcher genomes on a panel of 48 different bird species. In total, 162 cases (species/marker combinations) of heterologous amplification were recorded. Ten amplification products were sequenced and all were found to be true homologues of the original loci. There was a significant and negative relationship between microsatellite performance and evolutionary distance between the original species and the tested species. As a rough indicator of expected cross-species microsatellite performance we estimate that 50% of markers will reveal polymorphism in a species with a DNA-DNA hybridization δT_mH value of 5 separating it from the original species. This corresponds to a divergence time of = 11 million years before present for passerine birds. The established relationship between performance and evolutionary distance agrees very well with data obtained from some mammalian species. The proportion of polymorphic loci among those markers that amplified decreased with increasing genetic distance, suggesting that few long repeats are preserved during evolution. One of the swallow markers, HrU2, amplified a specific product in all species analysed and will thus allow access to nuclear sequence data over a broad range of species. The only predictor of cross-species performance was the amount of non-specific amplification seen in the original species. An analysis of 10 species from within the family Hirundinidae with the swallow primers consistently revealed extensive polymorphism with average probabilities of identical genotypes ranging from 6 times 10^-4 to 6 times 10^-7. There were distinct allele frequency differences between the Hirundinidae species and we envisage that microsatellite cross-species amplification will be a useful tool in phylogeny construction and in species identification.     

The anatomy of the interspecific abundance–range size relationship for the British avifauna: II. Temporal dynamics

In a companion paper, we started an examination of the anatomy of the interspecific relationship between local abundance and geographical range size in the British avifauna by analysing its spatial dynamics. Here, we use the same data to extend this study to a consideration of the temporal dynamics of the relationship. Most species of British breeding bird show a positive intraspecific abundance–range size relationship through time: i.e. in years when a species is locally more abundant it also occupies a higher proportion of census sites. However, the majority of such relationships are not statistically significant, and other relationships that are statistically significant are negative. Therefore, intraspecific abundance–range size relationships do not simply mirror the relationship across species. Where they do arise, positive relationships are more likely to be associated with positive intraspecific relationships between range size and maximum rather than minimum abundance. The interspecific abundance–range size relationship is remarkably consistent across years, and is always significantly positive. The relationships for woodland and farmland census sites show correlated variation, so that in years when the linear regression slope and coefficient of determination are high across species on farmland plots, they also tend to be high across species on woodland plots. Common species tend to be common on both farmland and woodland plots, and tend to be common in all years. Likewise, rare species tend to be rare in all habitats and years. This concordance means that the positive interspecific abundance–range size relationship can be viewed as occurring largely independently of intraspecific relationships. It follows from the above that developing an understanding of intraspecific abundance–range size relationships may be of only limited value in ascertaining the determinants of positive interspecific abundance–range size relationships. We conclude that for interspecific relationships, it will be important to know why some species are consistently common and others rare, whereas for intraspecific relationships it will be important to understand the dynamic links between local abundances across sites.     

The anatomy of the interspecific abundance–range size relationship for the British avifauna: I. Spatial patterns

Data from the British Trust for Ornithology Common Birds Census and two atlases of breeding birds were used to examine the form of the interspecific abundance–range size relationship for the British avifauna. The relationship is positive for both farmland and woodland habitats and over two different periods, with some evidence of curvilinearity, using either proportion of occupied sites or numbers of occupied 10 × 10 km squares as measures of range size, and mean density at occupied sites as a measure of abundance. A log-linear plot gives the highest correlation. The relationship is stronger if based on maximum local densities than if based on average densities, but there is no relationship using minimum local densities. Relationships based on abundances at individual sites are uniformly positive for all sites, although the relationships for many sites also show evidence of curvilinearity, especially when range size is measured as the proportion of occupied sites. Species show significant concordance in their rank abundances across sites. We discuss some implications of these results.     

气候变化对鸟类影响的研究进展

气候变化对生物多样性的影响已成为热点问题.本文以鸟类为研究对象,根据鸟类受气候变化影响的最新研究成果,综述了气候变化对鸟类的分布、物候和种群等方面的影响.结果表明,在气候变化影响下,鸟类分布向高纬度或高海拔区移动,速度比以往加快,繁殖地和非繁殖地的分布移动变化并不相同,并且多数分布范围缩小,物候期发生复杂变化,种群数量下降明显.文章还讨论了该领域主要的预测和评估方法,以及进化适应等生物因素对气候变化预测结果的影响,除了以往单一的相关性模型外,目前应用最多的是集成模型,而未来最具发展潜力的是机理模型.进化适应方面的研究近来取得新进展,证实了生物个体积极应对气候变化影响的事实,从而对人为模型预测的准确性带来挑战.文章最后进行了总结和展望,结合国外研究经验和我国实际情况,提出一些建议:由于气候变化的影响及其研究是长期性的,从而对鸟类的历史监测数据提出很高的要求,当前我国急需建立一套长期、全面和可靠的鸟类数据监测系统;此外,人们需要综合评估现有各种预测模型的可靠性,在此基础上探索新的研究方法.     

Ecological correlates of geographical range occupancy in North American birds

Aim  The degree to which a species is predictably encountered within its range varies tremendously across species. Understanding why some species occur less frequently within their range than others has important consequences for conservation and for analyses of ecological patterns based on range maps. We examined whether patterns in geographical range occupancy can be explained by species-level traits.
Location  North America.
Methods  We used survey data from 1993 to 2002 from the North American Breeding Bird Survey along with digital range maps produced by NatureServe to calculate range occupancy for 298 species of terrestrial birds. We tested whether species traits explained variation in range occupancy values using linear regression techniques.
Results  We found three species traits that together explained more than half of the variation in range occupancy. Population density and niche breadth were positively correlated with occupancy, while niche position was negatively correlated with occupancy.
Main conclusions  Our results suggest that high range occupancy will occur in species that are common at sites on which they occur, that tolerate a relatively wide range of ecological conditions and that tend to have ranges centred on areas with common environmental conditions. Furthermore, it appears that niche-based characteristics may explain patterns of distribution and abundance from local habitats up to the scale of geographical ranges.     

Some new approaches to conservation monitoring of British breeding birds

It is important to monitor bird populations both in their own right and as indicators of the general health of wildlife habitats. The objectives of the British Trust for Ornithology's Integrated Population Monitoring programme relate to breeding bird populations in Britain and Ireland and involve the estimation of demographic parameters as well as assessment of numbers. Current programmes for monitoring bird numbers cover the majority of British species; it would be feasible to monitor most of the rest. A new Breeding Bird Survey has been developed to provide effective coverage of all regions and all major habitats in Britain through random sampling, allowing for the marked geographical variation in volunteer observer density. The final choice of a random sample stratified by observer density (with some professional support in regions with few volunteer observers) was based on comparison with alternative stratifications, using data from a 2-year pilot study to assess the number of species adequately covered under various alternatives. A method of assessing whether or not targets are being achieved at any time has been developed: it involves looking back through the data at intervals of 1-year, 4-year, 16-year and longer spans. It will be possible to refine this by incorporating environmental and density-dependent effects into predictive models. The method is illustrated here using Common Birds Census data. We discuss associated problems of statistical inference and of taking decisions under uncertainty. The data provide evidence for large declines in some species, particularly in farmland; the value of birds as general indicators of habitat health is clear. The results of monitoring can be used to illuminate possible causes of problems and to guide both practical steps to ameliorate the problems and research aimed at better understanding the causes. Examples of such research are discussed.