Anthropogenically-Mediated Density Dependence in a Declining Farmland Bird

Land management intrinsically influences the distribution of animals and can consequently alter the potential for density-dependent processes to act within populations. For declining species, high densities of breeding territories are typically considered to represent productive populations. However, as density-dependent effects of food limitation or predator pressure may occur (especially when species are dependent upon separate nesting and foraging habitats), high territory density may limit per-capita productivity. Here, we use a declining but widespread European farmland bird, the yellowhammer Emberiza citrinella L., as a model system to test whether higher territory densities result in lower fledging success, parental provisioning rates or nestling growth rates compared to lower densities. Organic landscapes held higher territory densities, but nests on organic farms fledged fewer nestlings, translating to a 5 times higher rate of population shrinkage on organic farms compared to conventional. In addition, when parental provisioning behaviour was not restricted by predation risk (i.e., at times of low corvid activity), nestling provisioning rates were higher at lower territory densities, resulting in a much greater increase in nestling mass in low density areas, suggesting that food limitation occurred at high densities. These findings in turn suggest an ecological trap, whereby preferred nesting habitat does not provide sufficient food for rearing nestlings at high population density, creating a population sink. Habitat management for farmland birds should focus not simply on creating a high nesting density, but also on ensuring heterogeneous habitats to provide food resources in close proximity to nesting birds, even if this occurs through potentially restricting overall nest density but increasing population-level breeding success.     

Modelling Annual Numbers of Bird Territories on Farmland Plots

The Common Birds Census of the British Trust for Ornithology provides extensive data from which it is possible to attempt to explain some aspects of the population dynamics of common bird species. Such data are examined here. A consistent, striking feature of the data is noted when a second order model is fitted to estimated numbers of territory-holding birds in successive years. Alternative approaches to explaining the observed nature of the data are presented, including the development of simple birth-death-maturation (-immigration) models.     

Habitat-Specific variation in eyespot size of a benthic cladoceran

Summary Pigmented eyespot size of the benthic cladoceran Simocephalus exspinosus was measured in individuals sampled from four freshwater ponds that differed in the extent of visually-oriented predation. In ponds with such predation (from fish, salamander larvae, and dragonfly nymphs), eyespot size was found to be significantly smaller, relative to body size, than in a pond without visually-oriented predation. Reduction in pigmented eyespot size may represent an adaptation to reduce vulnerability to predation.     

辨析种群增长率与种群增长速率一字之差

种群既是生物繁殖的基本单位,也是生物进化的基本单位.它是生态学中一个核心概念,现已成为每年高考必考内容之一.其中有关种群增长的问题是多年高考命题热点,种群增长率与种群增长速率虽然只有一字之差.     

No Association between Personality and Candidate Gene Polymorphisms in a Wild Bird Population

Consistency of between-individual differences in behaviour or personality is a phenomenon in populations that can have ecological consequences and evolutionary potential. One way that behaviour can evolve is to have a genetic basis. Identifying the molecular genetic basis of personality could therefore provide insight into how and why such variation is maintained, particularly in natural populations. Previously identified candidate genes for personality in birds include the dopamine receptor D4 (DRD4), and serotonin transporter (SERT). Studies of wild bird populations have shown that exploratory and bold behaviours are associated with polymorphisms in both DRD4 and SERT. Here we tested for polymorphisms in DRD4 and SERT in the Seychelles warbler (Acrocephalus sechellensis) population on Cousin Island, Seychelles, and then investigated correlations between personality and polymorphisms in these genes. We found no genetic variation in DRD4, but identified four polymorphisms in SERT that clustered into five haplotypes. There was no correlation between bold or exploratory behaviours and SERT polymorphisms/haplotypes. The null result was not due to lack of power, and indicates that there was no association between these behaviours and variation in the candidate genes tested in this population. These null findings provide important data to facilitate representative future meta-analyses on candidate personality genes.     

Very Low Population Structure in a Highly Mobile and Wide-Ranging Endangered Bird Species

The loss of biodiversity following fragmentation and degradation of habitat is a major issue in conservation biology. As competition for resources increases following habitat loss and fragmentation, severe population declines may occur even in common, highly mobile species; such demographic decline may cause changes within the population structure of the species. The regent honeyeater, Anthochaera phrygia, is a highly nomadic woodland bird once common in its native southeast Australia. It has experienced a sharp decline in abundance since the late 1970s, following clearing of large areas of its preferred habitat, box-ironbark woodland, within the last 200 years. A captive breeding program has been established as part of efforts to restore this species. This study used genetic data to examine the range-wide population structure of regent honeyeaters, including spatial structure, its change through time, sex differences in philopatry and mobility, and genetic differences between the captive and wild populations. There was low genetic differentiation between birds captured in different geographic areas. Despite the recent demographic decline, low spatial structure appears to have some temporal consistency. Both sexes appear to be highly mobile, and there does not seem to be significant genetic differentiation between the captive and wild populations. We conclude that management efforts for survival of this species, including habitat protection, restoration, and release of captive-bred birds into the wild, can treat the species as effectively a single genetic population.     

Structure and Distribution of the Bird Population in Innermountain Dagestan

This paper analyses the results of bird counts carried out over the period of 1996–2017 in the Innermountain Province of Dagestan. The avian species composition, average population abundance, and ecological pattern of avifauna in a difficult-to-reach mountain area of the republic are described for the first time. Cluster analysis showed that population patterns of the considered sampling areas were not only similar, but also unique because of high heterogeneity of habitats and, consequently, faunal differences, which emerge in mountains under a lack of humidification. It is suggested that a specific pattern of the avifauna of Innermountain Dagestan is provided not only by resident communities of typical mountain birds, but also by adapted populations composed of migratory birds of valleys that nest in mountains.     

大理洱海西岸农耕区鸟类多样性

2011年在大理洱海西岸农耕区选择5片调查样区,每个样区布设1条调查样线,采用不定宽样线法对鸟类物种和数量及其栖息生境进行了4个季节的观察记录,共记录鸟类87种,隶属11目25科。研究结果表明秋季鸟类多样性最高;不同生境类型中,防护林内的鸟类多样性最高。以小时为单位统计每小时遇见鸟类个体数,春季为70.71只,夏季为79.36只,秋季为76.65只,冬季为70.37只。     

Population Differentiation in a Complex Bird Sound: A Comparison of Three Bioacoustical Analysis Procedures

We examined three bioacoustical analysis methods for comparing complex sounds among different populations. We chose the D‐syllable of the chick‐a‐dee call of the black‐capped chickadee (Poecile atricapilla) because it is a broadband sound representative of a class of vocalizations, common in many animals, that resists simple subjective classification for comparative studies. We examined the properties of the D‐syllable in field‐recorded samples from three different populations. The first method of data extraction sampled the amplitude values of a spectrum obtained in a single fast Fourier transform (SFFT) taken at the midpoint of each D‐syllable using multi‐speech software. The second method employed spectrogram cross‐correlation (SPCC) to obtain a matrix of similarity values between D‐syllables in the samples using canary software. The third method calculated similarity values obtained from the evaluation of four acoustic features of the D‐syllables derived from multi‐taper spectral analysis (MTSA) using sound analysis software. Following data extraction by these three techniques, we used multivariate statistical procedures to reduce the data for examination of differences among populations and to represent in scatter‐plots the patterns of clustering of the sounds. We found that the SFFT in the middle of the D‐syllable provided the poorest population discrimination following statistical processing, the SPCC method produced the next clearest population separation, and the MTSA method resulted in the most distinct separation of the three populations of D‐syllables. In carrying out these comparisons, we discovered that the characteristic environmental noise of a recording area can influence the signal properties of broadband sounds being compared by automated procedures, and could lead to faulty conclusions unless appropriate care is taken to mitigate the noise in which the signals of interest are embedded. Consequently we re‐analyzed our data following noise reduction and found less discrete population separation overall. However, the methods of SPCC and MTSA retained the ability to separate populations, with MTSA providing the sharpest discrimination among groups.     

Modelling the European Farmland Bird Indicator in response to forecast land-use change in Europe

The European Farmland Bird Indicator (EFBI) has been adopted as a Structural and Sustainable Development Indicator by the European Union. It is an aggregated index integrating the population trends of 33 common bird species associated with farmland habitats across 21 countries. We describe a modelling method for predicting this indicator from land-use characteristics. Using yearly historical land-use data of crop areas derived from the FAO databases (1990–2007) and published population data of farmland birds at the national level for the same period, we developed a series of multiple regression models to predict the trend of the EU state specific indicator, and the EFBI. These models incorporated up to 4 parameters and were selected based upon the significance (p < 0.05) of the model inputs with respect to the predictive variable. 17 separate models were developed in total for each of 14 EU countries plus Norway and Switzerland, and a separate model for the EU level indicator. The selected models were then implemented to predict the EFBI in the year 2025, using scenarios of land-use change generated by the CAPRI agricultural model. The uncertainty of using the regression models is discussed with respect to predicting the likely impacts of land-use change on bird populations. This work lays the framework for future modelling of farmland birds at the international scale.     

Two Models of Population Growth

Two simple models of the ecology of population growth are described: "exponential" growth with "r -selection," and "logistic" growth, with "K- selection." Various methods for estimating the parameters of these models are presented in detail, along with statistical methods of evaluation and comparison. Also briefly discussed are more complex models of population growth sometimes used by demographers and ecologists. The two simpler models of population growth are then applied, by way of illustration, to two episodes of population growth in protohistoric southwest Iran, dating from 4000–2350 B. C. Interpretation of the results and the implications for future research are then discussed . [population growth, statistical models, exponential growth, logistic growth, early Iran]     

一类单种群增长模型正解的振动性

利用一种新的方法研究了一类单种群增长模型—时滞微分方程N(t)=的解关于其正平衡点N=1的振动性,所获结果改进了已有文献中的相关结论。     

Signature of a Pre-Human Population Decline in the Critically Endangered Reunion Island Endemic Forest Bird Coracina newtoni

The exceptional biodiversity of Reunion Island is threatened by anthropogenic landscape changes that took place during the 350 years of human colonization. During this period the human population size increased dramatically from 250 to 800,000. The arrival of humans together with the development of agriculture, invasive species such as rats and cats, and deforestation has lead to the extinction of more than half of the original vertebrate species of the island. For the remaining species, significant work is being carried out to identify threats and conservation status, but little genetic work has been carried on some of the most endangered species. In the last decade theoretical studies have shown the ability of neutral genetic markers to infer the demographic history of endangered species and identify and date past population size changes (expansions or bottlenecks). In this study we provide the first genetic data on the critically endangered species the Reunion cuckoo-shrike Coracina newtoni. The Reunion cuckoo-shrike is a rare endemic forest bird surviving in a restricted 12-km(2) area of forested uplands and mountains. The total known population consists of less than one hundred individuals out of which 45 were genotyped using seventeen polymorphic microsatellite loci. We found a limited level of genetic variability and weak population structure, probably due to the limited geographic distribution. Using Bayesian methods, we identified a strong decline in population size during the Holocene, most likely caused by an ancient climatic or volcanic event around 5000 years ago. This result was surprising as it appeared in apparent contradiction with the accepted theory of recent population collapse due to deforestation and predator introduction. These results suggest that new methods allowing for more complex demographic models are necessary to reconstruct the demographic history of populations.