Patterns of seasonal and yearly mass variation in West African tropical savannah birds

Birds in the northern hemisphere usually increase mass reserves in response to seasonal low temperatures and shorter day length that increase foraging unpredictability and so starvation risk. In the lowland tropics, relatively low temperatures and short day lengths are absent and so the risk of starvation may be reduced, leading to much smaller seasonal effects on mass. Nevertheless, other factors such as high temperatures and water and food availability may vary greatly between tropical wet and dry seasons, leading to variable starvation risk and seasonal mass effects. Using data collected from 47 species of birds caught over a 10‐year period in a tropical savannah region in West Africa we tested for seasonal variation in mass in response to a predictable, strongly seasonal tropical climate. Many species (91%) showed seasonal variation in mass, and this was often in a clear annual pattern that was constant across the years. Many species (89%) varied their mass in response to seasonally predictable rainfall. Annual variation in mass was also important (45% of species). Relatively few species (13%) had a seasonal pattern of mass variation that varied between years. Feeding guild or migratory status was not found to affect seasonal or annual mass variation. Seasonal mass change was on average 8.1% across the 21 species with a very large sample size and was comparable with both northern and southern temperate species. Our study showed that biologically significant consistent seasonal mass variation is common in tropical savannah bird species, and this is most likely in response to changing resource availability brought about by seasonal rainfall and the interrupted foraging response due to the constraints of breeding.     

西双版纳热带季节雨林的研究

本文以多个样方的资料分析,从群落综合特征上研究了西双版纳热带季节雨林的特点和类型、物种组成、生活型谱、叶级谱等。根据上层标志树种、群落生态外貌特征和生境把西双版纳的热带季节雨林区分为低丘雨林和沟谷雨林二个群系组,各包括若干群系。低丘雨林中面积最大和最有代表性的群系是大药树、龙果林,而沟谷雨林中最有代表性的群系是番龙眼、千果榄仁林。二者相比,低丘雨林的物种多样性要小一些,附生植物相对少一些,小、矮高位芽植物和小叶、落叶树种比例稍高,在生态上向季雨林和热带山地的常绿阔叶林过渡,有更强的地方代表性。沟谷雨林则更接近典型的湿热带雨林。     

A longitudinal large-scale objective sleep data analysis revealed a seasonal sleep variation in the Japanese population

In the contemporary era, when life habits are largely determined by social needs and individual preferences, sleep is nevertheless affected by seasonal environmental changes. Japan has large seasonal and geographical alterations of photoperiod and climate. Japan does not adopt the daylight saving time (DST) system, making it a suitable country for the study of seasonal variations in natural human sleep. The aim of this study was to analyze the seasonal changes in the sleep properties (timing and quality) and identify their relationship with environmental changes. Here, we report an analysis of objective sleep data of 691 161 nights collected from 1856 Japanese participants (age 20–79 years, male 91%, female 9%) for 3 years using contactless biomotion sensors. Sleep onset time did not show clear seasonal variation, but sleep offset time showed a seasonal change with a single latest peak in winter. Seasonal variation was larger during weekends than during weekdays. Sleep offset time well correlated with sunrise time but was different in spring and autumn even when the sunrise time was same, suggesting the role of temperature difference. Sleep quality, estimated by wake time after sleep onset and sleep efficiency, showed seasonal changes with the lowest trough around mid-summer. In conclusion, despite profound social influences, the timing and quality of sleep showed seasonal fluctuation indicating that they were influenced by climate factors even in the developed country.     

Breeding birds associated with seasonal pools in the northeastern United States

ABSTRACT Seasonal pools in the northeastern United States provide habitat for amphibians and invertebrates, but little is known about their importance as habitat for birds. We examined avian community composition at seasonal pools in Rhode Island to test the hypothesis that seasonal pools would support a greater abundance and diversity of birds than nearby upland sites. From mid‐May to June 2008, we conducted point counts at 33 paired sets of seasonal pools and upland sites that were 150 m apart. Bird abundance and diversity was significantly higher at seasonal pools than upland sites, whereas community composition as measured by evenness was similar. We also found that the mean abundance of birds was significantly greater at urban pools than rural pools. Our results suggest that birds preferentially use seasonal pools, particularly in more urban settings, adding to the body of evidence that supports the protection and restoration of small isolated wetlands in urban landscapes.     

Limnological observations of an intermittent tropical dry forest stream

This study examines aspects of the seasonal limnology of an intermittent stream in the dry forest region of northwest Costa Rica. It focuses on annual water level fluctuations and both seasonal and among pool variation in dissolved oxygen concentration and water temperature. Dry season pools differed in morphometry and the rate of decline in water levels subsequent to the seasonal floods. Rate of water level decline was related both to pool depth and to the exposure of the pool to the sun. Oxygen concentration was generally low in the dry season, but increased during the rainy season in association with rain events and seasonal flooding. A repeated-measures analysis of variance indicated that seasonal effects accounted for 40% of the variance in oxygen concentration for residual pools. Differences among pools were also significant. However, there was strong evidence for a significant interaction between seasonal and spatial influences on oxygen values in the system. Variation in water temperature was small, but differences among pools, sampling dates, and their interaction were all significant. Periphyton production increased significantly between the late wet season sample in November and the dry season sample in February. Incident light intensity explained 76% of the variation among pools in net periphyton production in the dry season.     

Seasonal cycles in the blood plasma concentration of FSH, inhibin and testosterone, and testicular size in rams of wild, feral and domesticated breeds of sheep

Seasonal cycles in testicular activity in rams were monitored in groups of wild (mouflon), feral (Soay) and domesticated breeds of sheep (Shetland, Blackface, Herdwick, Norfolk, Wiltshire, Portland and Merino) living outdoors near Edinburgh (56 degrees N). The changes in the blood plasma concentrations of FSH, inhibin and testosterone, and the diameter of the testis were measured every half calendar month from 1 to 3 years of age. There were significant differences between breeds in the magnitude and timing of the seasonal reproductive cycle. In the mouflon rams, the seasonal changes were very pronounced with a 6-15-fold increase in the plasma concentrations of FSH, inhibin and testosterone from summer to autumn, and a late peak in testicular diameter in October. In the Soay rams and most of the domesticated breeds, the seasonal increase in the reproductive hormones occurred 1-2 months earlier with the peak in testicular size in September or October. In the two southern breeds (Portland and Merino), the early onset of testicular activity was more extreme with the seasonal maximum in August. In cross-bred rams, produced by mating Soay ewes (highly seasonal breed) with Portland or Merino rams (less seasonal breeds), there was a seasonal reproductive cycle that was intermediate compared to that of the parents. A comparison between all 11 breeds showed a significant correlation between the timing of the seasonal cycle in plasma FSH concentration and testicular diameter (time of peak FSH vs testis, r = 0.95). The overall results in the rams are consistent with a primary role of FSH in dictating the seasonal cycle in testicular size and the secretion of inhibin. The earlier seasonal onset in the testicular cycle in the southern breeds of domesticated sheep, and the differences from the wild type, are taken to represent the effects of genetic selection for a longer mating season.     

Vertical Distribution of Tintinnopsis lacustris (ENTZ) and Tintinnidium fluviatile STEIN (Ciliata) in Lake Kozjak (Plitvice Lakes), Yugoslavia

The seasonal changes in the vertical distribution of Tintinnopsis lacustris and Tintinnidium fluviatile was studied in the Karst Lake Kozjak, one of the group of Plitvice lakes. The question asked was to what extent does the development of these two species-populations follow the seasonal fluctuations and spatial distributions of the planktonic community or the seasonal changes in environmental conditions.     

Songbird frequency selectivity and temporal resolution vary with sex and season

Many species of songbirds exhibit dramatic seasonal variation in song output. Recent evidence suggests that seasonal changes in auditory processing are coincident with seasonal variation in vocal output. Here, we show, for the first time, that frequency selectivity and temporal resolution of the songbird auditory periphery change seasonally and in a sex-specific manner. Male and female house sparrows (Passer domesticus) did not differ in their frequency sensitivity during the non-breeding season, nor did they differ in their temporal resolution. By contrast, female house sparrows showed enhanced frequency selectivity during the breeding season, which was matched by a concomitant reduction of temporal resolution. However, males failed to show seasonal plasticity in either of these auditory properties. We discuss potential mechanisms generating these seasonal patterns and the implications of sex-specific seasonal changes in auditory processing for vocal communication.     

Seasonal variation in Plasmodium prevalence in a population of blue tits Cyanistes caeruleus

1. Seasonal variation in environmental conditions is ubiquitous and can affect the spread of infectious diseases. Understanding seasonal patterns of disease incidence can help to identify mechanisms, such as the demography of hosts and vectors, which influence parasite transmission dynamics. 2. We examined seasonal variation in Plasmodium infection in a blue tit Cyanistes caeruleus population over 3 years using sensitive molecular diagnostic techniques, in light of Beaudoin et al.'s (1971; Journal of Wildlife Diseases, 7, 5-13) model of seasonal variation in avian malaria prevalence in temperate areas. This model predicts a within-year bimodal pattern of spring and autumn peaks with a winter absence of infection. 3. Avian malaria infections were mostly Plasmodium (24.4%) with occasional Haemoproteus infections (0.8%). Statistical nonlinear smoothing techniques applied to longitudinal presence/absence data revealed marked temporal variation in Plasmodium prevalence, which apparently showed a within-year bimodal pattern similar to Beaudoin et al.'s model. However, of the two Plasmodium morphospecies accounting for most infections, only the seasonal pattern of Plasmodium circumflexum supported Beaudoin et al.'s model. On closer examination there was also considerable age structure in infection: Beaudoin et al.'s seasonal pattern was observed only in first year and not older birds. Plasmodium relictum prevalence was less seasonally variable. 4. For these two Plasmodium morphospecies, we reject Beaudoin et al.'s model as it does not survive closer scrutiny of the complexities of seasonal variation among Plasmodium morphospecies and host age classes. Studies of host-parasite interactions should consider seasonal variation whenever possible. We discuss the ecological and evolutionary implications of seasonal variation in disease prevalence.     

Peripheral melatonin modulates seasonal immunity and reproduction of Indian tropical male bird Perdicula asiatica

Seasonal changes in pineal function are well coordinated with seasonal reproductive activity of tropical birds. Further, immunomodulatory property of melatonin is well documented in seasonally breeding animals. Present study elucidates the interaction of peripheral melatonin with seasonal pattern of immunity and reproduction in Indian tropical male bird Perdicula asiatica. Significant seasonal changes were noted in pineal, testicular and immune function(s) of this avian species. Maximum pineal activity along with high immune status was noted during winter month while maximum testicular activity with low immune status was noted in summer. During summer month's long photoperiod suppressed pineal activity and high circulating testosterone suppressed immune parameters, while in winter short photoperiod elevated pineal activity and high circulating melatonin maintained high immune status and suppressed gonadal activity. Therefore, seasonal levels of melatonin act like a major temporal synchronizer to maintain not only the seasonal reproduction but also immune adaptability of this avian species.     

Quantitative analysis of seasonal dynamics of the species structure in a component parasite community of the minnow Phoxinus phoxinus (L.) of the Pechora River

Earlier analysis of a seasonal succession of fish parasites assemblage was, as a rule, performed in May-October. At the same time, winter season can be important in seasonal dynamics of the assemblage. In the present work, quantitative analysis of complete seasonal dynamics of species structure of fish assemblage parasites with an example of the adult minnow of the river Pechora was performed. The new stable state of parasites assemblage of the minnow, corresponding to winter season of its existence, is revealed. Irrespective of population density or a biomass of parasitic assemblages of the minnow, obtained dynamic phase portraits well reflect their seasonal succession.     

SEASONAL MORTALITY PATTERNS IN NON‐HUMAN PRIMATES: IMPLICATIONS FOR VARIATION IN SELECTION PRESSURES ACROSS ENVIRONMENTS

Examining seasonal mortality patterns can yield insights into the drivers of mortality and thus potential selection pressures acting on individuals in different environments. We compiled adult and juvenile mortality data from nine wild non‐human primate taxa to investigate the role of seasonality in patterns of mortality and address the following questions: Is mortality highly seasonal across species? Does greater environmental seasonality lead to more seasonal mortality patterns? If mortality is seasonal, is it higher during wet seasons or during periods of food scarcity? and Do folivores show less seasonal mortality than frugivores? We found seasonal mortality patterns in five of nine taxa, and mortality was more often tied to wet seasons than food‐scarce periods, a relationship that may be driven by disease. Controlling for phylogeny, we found a positive relationship between the degree of environmental seasonality and mortality, with folivores exhibiting more seasonal mortality than frugivores. These results suggest that mortality patterns are influenced both by diet and degree of environmental seasonality. Applied to a wider array of taxa, analyses of seasonal mortality patterns may aid understanding of life‐history evolution and selection pressures acting across a broad spectrum of environments and spatial and temporal scales.     

荒漠草原区柠条固沙人工林地表草本植被季节变化特征

研究荒漠草原人工林固沙区地表草本植被季节变化特征及其和柠条林龄的关系,对于分析柠条人工林地表草本植物的季节适应性和制订合理的人工林管理措施均具有重要的科学意义。选择6、15、24年生和36年生柠条人工林为研究对象,通过调查每个样地5月、8月和10月地表草本植物密度、物种数、盖度和高度,分析了荒漠草原区柠条人工固沙林生长过程中地表草本植被季节变化特征及其影响因素。结果表明,地表草本植物物种数在柠条林龄6和15a时受季节改变的影响较小,在24a之后受到季节变化的显著影响(P0.05)。地表草本植物密度在柠条林龄6a时受季节改变的影响较小,但在15a之后季节变化显著影响地表草本植物个体数分布(P0.05),而且在10月具有最多的地表草本植物个体数。地表草本植被盖度和高度均受到季节变化的显著影响(P0.05),而受林龄的影响较小;不同年龄林地地表草本植被盖度和高度均表现为10月和8月较高,5月较低。研究表明,荒漠草原柠条人工林固沙区,柠条林发育生长和灌木形态的改变不仅影响土壤营养条件,而且还可以调控由于季节改变而引起的土壤温湿度变化,柠条林龄和季节更替二者交互作用,共同影响地表草本植被的季节变化特征。     

Evidence for strong seasonality in the carbon storage and carbon use efficiency of an Amazonian forest

The relative contribution of gross primary production and ecosystem respiration to seasonal changes in the net carbon flux of tropical forests remains poorly quantified by both modelling and field studies. We use data assimilation to combine nine ecological time series from an eastern Amazonian forest, with mass balance constraints from an ecosystem carbon cycle model. The resulting analysis quantifies, with uncertainty estimates, the seasonal changes in the net carbon flux of a tropical rainforest which experiences a pronounced dry season. We show that the carbon accumulation in this forest was four times greater in the dry season than in the wet season and that this was accompanied by a 5% increase in the carbon use efficiency. This seasonal response was caused by a dry season increase in gross primary productivity, in response to radiation and a similar magnitude decrease in heterotrophic respiration, in response to drying soils. The analysis also predicts increased carbon allocation to leaves and wood in the wet season, and greater allocation to fine roots in the dry season. This study demonstrates implementation of seasonal variations in parameters better enables models to simulate observed patterns in data. In particular, we highlight the necessity to simulate the seasonal patterns of heterotrophic respiration to accurately simulate the net carbon flux seasonal tropical forest.     

Seasonal plasticity of duodenal morphology and histology in Passer montanus

When facing seasonal environmental changes, flying birds and small mammals may develop adaptive gastrointestinal changes to optimize their digestive and absorptive strategies to meet the changing of physiologic needs. As a main component of gastrointestinal tract, small intestine is extraordinarily sensitive to food abundance, food quality, and other environmental factors. However, the detailed morphological adaptations of the small intestine during seasonal changes are largely unknown. Here, we studied the morphological and histological dynamics of duodenum from Passer montanus in Zhalong Nature Reserve in China during seasonal changes. The luminal and wall cross-section area were greater in spring and autumn than that in summer. Villus height and width went up to peak values in winter and showed similar seasonal dynamic changes with that of mucosal thickness, while villus atrophy accompanied by the deepest crypt depth was easily detected in summer. Epithelium thickness was coincident with villus atrophy except a sharp increase in summer. Submucosal thickness was negatively correlated with that of mucosa, while the size, but not total number, of duodenal glands was altered to reflect to seasonal changes. Neither the inner circular nor the outer longitudinal muscle showed seasonal morphological changes, indicating the relatively stable plasticity of intestine muscle structures. Taken together, we propose that phenotypic flexibility in digestive morphology and histology enables small birds to cope with remarkable seasonal changes.     

Long-term seasonal variation in the biological traits of benthic-macroinvertebrates in two Mediterranean-climate streams in California, U.S.A.

1. We investigated the seasonal variation of biological traits and the influence of interannual rainfall variability on this pattern. Using long‐term survey data (6–19 years) from an intermittent and a perennial stream in the Mediterranean‐climate region of northern California, we examined 16 fuzzy‐coded biological traits (e.g. maximum size, life cycle duration, and mode of respiration). 2. Seasonal habitat variability is higher in the intermittent stream than in the perennial stream. During the winter and spring wet‐season both streams flood; however, during the summer dry‐season, the intermittent stream forms isolated pools in (occasionally drying completely). 3. Seasonal habitat variability influenced both taxonomic and biological trait composition. Distinct taxonomic communities were present in each season, particularly in the intermittent stream. The intermittent stream also exhibited more seasonal variation in biological traits than the perennial stream. 4. Despite statistically significant seasonal variation, trait composition was relatively stable among seasons in comparison with taxonomic composition and abundance. Taxonomic composition varied considerably between seasons, because of high seasonal and interannual replacement of taxa resulting from seasonal habitat changes. 5. The seasonality of taxonomic composition and abundance was sensitive to interannual rainfall variability. In dry years, the taxonomic composition of communities was more similar between seasons than in wet years, while trait composition was relatively insensitive to rainfall variability. 6. Despite high seasonal variation in abundance and taxonomic composition, biological traits of aquatic macroinvertebrates varied less and exhibited seasonal stability, which may be a result of the unpredictability and harshness of stream environments.     

Seasonal Variation of Newly Notified Pulmonary Tuberculosis Cases from 2004 to 2013 in Wuhan,China

Background

Although there was a report about the seasonal variation in Wuhan city, it only analyzed the prevalence data of pulmonary tuberculosis (TB) cases, and just studied the seasonality by subgroup of smear positive and negative from 2006 to 2010 by spectral analysis. In this study, we investigated the seasonality of the total newly notified pulmonary TB cases by subgroups such as time period, sex, age, occupation, district, and sputum smear result from 2004 to 2013 in Wuhan by a popular seasonal adjustment model (TRAMO-SEATS).

Methods

Monthly pulmonary TB cases from 2004 to 2013 in Wuhan were analyzed by the TRAMO-SEATS seasonal adjustment program. Seasonal amplitude was calculated and compared within the subgroups.

Results

From 2004 to 2013, there were 77.76 thousand newly notified pulmonary TB cases in Wuhan, China. There was a dominant peak spring peak (March) with seasonal amplitude of 56.81% and a second summer peak (September) of 43.40%, compared with the trough month (December). The spring seasonal amplitude in 2004–2008 was higher than that of 2009–2013(P<0.05). There were no statistical differences for spring seasonal amplitude within subgroups of gender, age, district, and sputum smear result (P>0.05). However, there were significant differences in spring seasonal amplitude by occupation, with amplitude ranging from 59.37% to 113.22% (P<0.05). The summer seasonal amplitude in 2004–2008 was higher than that of 2009–2013(P<0.05). There were no statistical differences in summer seasonal amplitude within subgroups of gender, district, sputum smear result(P>0.05). There were significant differences in summer seasonal amplitude by age, with amplitude ranging from 36.05% to 100.09% (P<0.05). Also, there were significant differences in summer seasonal amplitude by occupation, with amplitude ranging from 43.40% to 109.88% (P<0.05).

Conclusions

There was an apparent seasonal variation in pulmonary TB cases in Wuhan. We speculated that spring peak in our study was most likely caused by the increased reactivation of the latent TB due to vitamin D deficiency and high PM2.5 concentration, while the summer peak was mainly resulted from the enhanced winter transmission due to indoor crowding in winter, overcrowding of public transportation over the period of the Spring Festival and health care seeking delay in winter.     

Coexistence of cryptic rotifer species: ecological and genetic characterisation of Brachionus plicatilis

1. The coexistence of five cryptic species of the rotifer species complex Brachionus plicatilis was investigated in four coastal Mediterranean ponds. Monthly sampling was undertaken for 15 months and species were characterised using allozyme electrophoresis. 2. We describe species‐diagnostic allozyme loci that can be used for rapid identification of these species. 3. The five species overlapped to some extent in their temporal use of the ponds, although some seasonal segregation was observed. 4. The match between temporal and spatial distribution and limnological conditions suggested ecological specialisation in some cases, although we found striking examples of extensive seasonal overlap. 5. Our results indicate that sympatry of cryptic rotifer species is largely because of seasonal ecological specialisation, which allows seasonal succession and partitioning of resources. The processes that might be involved in the long periods of overlapping seasonal distributions of species which are potentially competitors are discussed. This example illustrates that the ‘paradox of the plankton’ is more the rule than the exception.     

Correlation with changes in horns and pelage, but not reproduction, of seasonal cycles in the secretion of prolactin in rams of wild, feral and domesticated breeds of sheep

Seasonal cycles were monitored in groups of wild (mouflon), feral (Soay) and domesticated breeds of sheep (Shetland, Blackface, Herdwick, Norfolk, Wiltshire, Portland, Merino, Soay x Portland and Soay x Merino) living outdoors near Edinburgh (56 degrees N). Changes in the blood plasma concentrations of prolactin and FSH, and growth of the horns and pelage were measured every half calendar month from 1 to 3 years of age. In all breeds there was a clearly defined seasonal cycle in the plasma concentration of prolactin with an 18-66-fold increase in mean values from the nadir in November and December to the peak in May and June. The seasonal increase in prolactin was closely correlated with the seasonal increase in the growth of the horns, both within and between breeds (e.g. time of peak prolactin vs horn growth for 11 breeds, R = 0.62, P less than 0.05). In the mouflon, Soay and some of the domesticated breeds of sheep (Wiltshire, Herdwick and Shetland), the seasonal increase in prolactin was also temporally correlated with the resurgence of growth of the pelage in spring and a conspicuous moult. In the other breeds developed to produce fine wool (e.g. Norfolk, Portland and Merino), there was no clear seasonal change in the pelage and growth continued throughout the year. Comparison between breeds indicated that continuous growth of the pelage was associated with higher plasma prolactin concentrations in winter. The times of the seasonal changes in plasma concentrations of prolactin were not significantly correlated with the corresponding changes in the plasma concentrations of FSH. The overall results are consistent with a role for prolactin related to the growth of the horns and pelage rather than the seasonal cycle in reproduction. The differences between the wild-type and the domesticated breeds in the pelage represent the effect of selective breeding to produce a long fine fleece which has involved changes in both the seasonal pattern of prolactin secretion and the growth characteristics of the hair fibres.