Sex- and age-related differences in the timing and body condition of migrating Reed Warblers Acrocephalus scirpaceus and Sedge Warblers Acrocephalus schoenobaenus

The migration strategies of birds may vary strongly between species and also between age and/or sex groups. We studied the autumn migration and body condition of molecularly sexed Reed Warblers Acrocephalus scirpaceus and Sedge Warblers Acrocephalus schoenobaenus (211 and 208 ind., respectively) at a stopover site on Lake Druzno, Northern Poland, in 2008. Immature male Reed Warblers were caught significantly later than females (median dates 9 days later), but in the Sedge Warbler, both sexes of immatures migrated at about the same time. Adult males and females of both species did not differ in their time of migration. Adult and immature males of both species were larger (wing length and body mass) than females. In both species, fat reserves were similar in both sexes of both age classes. Adults of both sexes of Reed and Sedge Warbler were generally caught earlier than immatures. In both species, the body mass and fat reserves of immatures were generally less than in adults. The autumn protogyny of immature Reed Warblers may allow smaller females to limit competition with bigger males during migration and at the wintering grounds. In the Sedge Warbler, which tends to match its migration to peak of occurrence of superabundant food at stopover sites, both sexes gain an advantage from migrating at the same time. Since part of the measured wing length variation in both species was explained by sex differences, temporal trends in wing length recorded at stopover sites should be interpreted with caution.     

Differential timing and latitudinal variation in sex ratio of Aquatic Warblers during the autumn migration

Differential migration has been extensively reported in spring, but less so in autumn, particularly in relation to sex in monomorphic bird species. Here, we analysed the autumn passage of a monomorphic, globally threatened passerine, the Aquatic Warbler Acrocephalus paludicola throughout Western Europe, with regard to age and sex. We showed that, overall, adults migrated earlier than first-year birds, and males migrated earlier than females during the autumn migration. This may be caused by an overall social dominance of adults over immatures, and differentiated migration strategy of males and females. In addition, we found male-skewed sex proportions, with a tendency to an equalised ratio in more southern stopover sites. This may indicate a male bias in the global population or different migration strategies of the sexes. Differential migration may cause the age and sex classes to be exposed differently to various threats affecting demographic structure of the species.     

Differential autumn migration of the aquatic warbler Acrocephalus paludicola

Relatively little attention has been paid to sex differences in the migration of birds in autumn. We studied the autumn migration strategy of molecularly sexed males and females in the globally threatened aquatic warbler Acrocephalus paludicola. We captured 176 birds at a stopover site in the Loire estuary at Donges, France. The median date for the passage of adults was 8 days earlier in males than females, although the timing of migration in first-year males and females was similar. This indicates that males, who are without parental duties, can start their migration earlier than females and first-year birds. Adults were significantly heavier than immature birds but did not have higher fat scores. In both age categories, more males (two to three times more) were captured. However, various factors (including tape-luring) can affect observed sex ratio.     

Light-dependent magnetoreception in birds: the effect of intensity of 565-nm green light

 In a previous study, Australian silvereyes tested in autumn under monochromatic 565-nm green light at intensities of 2.1 and 7.5 mW m^–2 preferred their normal northerly migratory direction, whereas they showed a significantly different tendency towards northwest at 15.0 mW m^–2. Repeating these experiments in spring with silvereyes migrating southward, we again observed well-oriented tendencies in the migratory direction at 2.1 and 7.5 mW m^–2. At 15.0 mW m^–2, however, the birds once more preferred northwesterly directions, i.e. their response under this condition proved to be independent of the migratory direction. This contradicts the interpretation that monochromatic green light of this high intensity leads to a rotation of compass information; instead, it appears to produce sensory input that causes birds to give up their migratory direction in favor of a fixed direction of as yet unknown origin. Received: 3 April 2000 / Accepted in revised form: 19 June 2000     

Emergence of long distance bird migrations: a new model integrating global climate changes

During modern birds history, climatic and environmental conditions have evolved on wide scales. In a continuously changing world, landbirds annual migrations emerged and developed. However, models accounting for the origins of these avian migrations were formulated with static ecogeographic perspectives. Here I reviewed Cenozoic paleoclimatic and paleontological data relative to the palearctic–paleotropical long distance (LD) migration system. This led to propose a new model for the origin of LD migrations, the ‘shifting home’ model (SHM). It is based on a dynamic perspective of climate evolution and may apply to the origins of most modern migrations. Non-migrant tropical African bird taxa were present at European latitudes during most of the Cenozoic. Their distribution limits shifted progressively toward modern tropical latitudes during periods of global cooling and increasing seasonality. In parallel, decreasing winter temperatures in the western Palearctic drove shifts of population winter ranges toward the equator. I propose that this induced the emergence of most short distance migrations, and in turn LD migrations. This model reconciliates ecologically tropical ancestry of most LD migrants with predominant winter range shifts, in accordance with requirements for heritable homing. In addition, it is more parsimonious than other non-exclusive models. Greater intrinsic plasticity of winter ranges implied by the SHM is supported by recently observed impacts of the present global warming on migrating birds. This may induce particular threats to some LD migrants. The ancestral, breeding homes of LD migrants were not ‘northern’ or ‘southern’ but shifted across high and middle latitudes while migrations emerged through winter range shifts themselves. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Reversed sex change by widowed males in polygynous and protogynous fishes: female removal experiments in the field

Sex change, either protogyny (female to male) or protandry (male to female), is well known among fishes, but evidence of bidirectional sex change or reversed sex change in natural populations is still very limited. This is the first report on female removal experiments for polygnous and protogynous fish species to induce reversed sex change in the widowed males in the field. We removed all of the females and juveniles from the territories of dominant males in the cleaner wrasse Labroides dimidiatus (Labridae) and the rusty angelfish Centropyge ferrugata (Pomacanthidae) on the coral reefs of Okinawa. In both species, if new females or juveniles did not immigrate into the territories of the widowed males, some of them emigrated to form male–male pairs. When a male–male pair formed, the smaller, subordinate partner began to perform female sexual behaviours (n = 4 in L. dimidiatus; n = 2 in C. ferrugata) and, finally, released eggs (n = 1, respectively). Thus, the reversed sex change occurred in the widowed males according to the change of their social status. These results suggest that such female removal experiments will contribute to the discovery of reversed sex change in the field also in other polygnous and protogynous species.     

Interannual differences in the relative timing of southward migration of male and female western sandpipers (Calidris mauri)

In the shorebird subfamily Calidridinae, one of the parents shortens parental care and initiates southward migration before the other. We estimated the difference in passage date between male and female western sandpipers (Calidris mauri) at their first major stopover on the southward migration from breeding areas in Alaska, in 18 years between 1978 and 2000. Overall, adult females preceded adult males by 1.22 days. A novel finding was that among juveniles, which migrate approximately a month later than adults, females preceded males by similar magnitude (1.14 days). There was wide variation among years, however, and males actually preceded females in years with late hatch. We relate these findings to hypotheses for female-first southward migration in sandpipers.     

Scale-dependent habitat selection in migratory frugivorous passerines

Frugivorous migrants may select fruit-rich habitats en route to attain high food rewards, yet their stopover behavior may also be shaped by other considerations, such as predation risk. During 1996–2001 we investigated autumn stopover habitat use of three Sylvia warblers (sylviids; S. hortensis, S. atricapilla and S. curruca) and three Turdidae chats (turdids; Cercotrichas galactotes, Oenanthe hispanica and Phoenicurus phoenicurus) in planted groves of the fruiting tree Pistacia atlantica in Lahav Forest, Israel, which is located at the edge of a desert. We used fecal analysis, a constant-effort trapping scheme and field observations to estimate the extent of frugivory, and bird habitat and microhabitat selection with regard to natural fruit and foliage densities. We also measured bird microhabitat selection in a set of fruit-manipulated trees. We trapped a total of 2,357 birds during the course of the study. Although sylviids exhibited higher frugivory level than turdids, both species groups exhibited a similar significantly positive correlation between bird and fruit densities at the habitat scale. However, at the microhabitat scale, sylviids selected densely foliated trees, whilst turdids were randomly distributed among trees. Our findings suggest that both species groups selected fruit-rich stopover habitats to take advantage of the high food availability before the demanding migration journey. No other mechanism except predation avoidance can explain the sylviids microhabitat selection; the migrants used foliage cover to reduce bird detectability by raptors. We conclude that en route passerines may use staging habitats in a sophisticated manner, by adopting scale-related behavior with regard to the availability of food and refuge cover.     

复合改良剂对Cd污染稻田早晚稻产地修复效果

选取湖南省长沙市北山镇某中重度Cd污染稻田,连续种植早晚两季水稻,研究复合改良剂(石灰石+硅藻土+硫酸铁)对稻田土壤重金属Cd的生物有效性和水稻各部位累积Cd的影响.结果表明,施用复合改良剂提高了早、晚稻土壤pH值、CEC值,降低了早稻土壤中有机质含量(OM值).Cd的TCLP提取态与交换态Cd含量分别降低了18.0%~33.0%、5.4%~57.9%,但对晚稻土壤中Cd的2种提取态含量与OM值影响不显著.施用复合改良剂显著降低早稻糙米、谷壳、茎叶、根系中的Cd含量,分别降低了29.6%~56.1%、52.1%~54.0%、18.1%~80.7%、24.4%~41.6%.早稻与晚稻之间对Cd的转运能力呈现明显差异,Cd在晚稻植株体内的转运过程更为通畅.晚稻除谷壳中的Cd含量在2 g·kg~(-1)的添加量下有所上升外,复合改良剂对水稻各部位Cd含量影响不显著(P0.05).糙米中Cd含量与土壤中TCLP可提取态含量和Cd的交换态含量存在显著正相关关系.复合改良剂有效地抑制了早稻植株对土壤中Cd的吸收,糙米中的Cd含量显著降低;晚稻期间复合改良剂随水分流失,不能持续地固化土壤中的Cd,建议在各季稻之间补加一次.     

The larval parasitoid <Emphasis Type="Italic">Microplitis croceipes</Emphasis> oviposits in conspecific adults

Microplitis croceipes (Hymenoptera: Braconidae) is a larval parasitoid of Helicoverpa/Heliothis spp. In the course of mass rearing of M. croceipes, we found that females oviposited in the conspecific adults in rearing cages. When 20 pairs of inexperienced females and males or of experienced females and males were reared in a cage, the males lived for 14–15 days and the females for 18–20 days on average. At their death, 37–42% of the males and 50–57% of the females contained conspecific eggs or first instar larvae in their abdominal cavity. When two of inexperienced females met on a host-infested leaf of soybean, they attempted to sting each other. Of the attacked females, 30% contained a conspecific egg laid in their abdomen. In abdominal cavity of the adults parasitized by a conspecific female, the majority of the parasitoid eggs laid disappeared within 1 day after oviposition. Only 10–30% of the parasitoid eggs laid in conspecific adults hatched 3–4 days after oviposition, but those larvae never molted to second instar. When the adults were stung by one or two conspecific females, their subsequent longevity was significantly shorter than that for the control adults. Oviposition in conspecific adults may be prevalent in other parasitic wasps that quickly oviposit without intensive host examination, and have cuticle and size of abdomen to be stung by conspeicifcs.     

Sex,age, spleen size,and kidney fat of red deer relative to infection intensities of the lungworm <Emphasis Type="Italic">Elaphostrongylus cervi</Emphasis>

We analyzed the relationships among spleen size, body condition (measured as kidney fat), and larval counts of the nematode Elaphostrongylus cervi in red deer (Cervus elaphus). The aim was to investigate the interaction between host body condition and intensity of infection with parasites. As red deer are highly polygynous, we also tested whether these relationships varied with sex and age of the hosts. Kidney fat and spleen size were positively correlated in subadults (2–3 years old) and adults (>3 years old), but not in calves (<1 year old) or yearlings (1–2 years old). Spleen size was negatively associated with nematode load in subadult females and in adult males. These two age classes are potentially the most nutritionally stressed, as subadult hinds are still growing and often engaging in rearing their first calf, and adult stags were sampled just after the rut, which is recognized as a substantial energy drain in this age–sex class, as they compete to hold females during the mating season. Body condition related negatively to parasite count only in adult males. In the context of red deer life history, these findings suggest that spleen size is dependent on body condition and that it could be affected by variation in resource partitioning among immune defense, growth, and reproductive effort in red deer. For the first time in a wild mammal, the spleen mass is shown to be positively related to body condition and negatively related to parasite infection. We conclude that elucidating whether spleen mass reflects immune defense investment or a measure of general body condition should contribute to understanding topical issues in mammal ecology.     

基于后向轨迹对城市大气中二噁英长距离迁移来源的探讨

通过对广州某商住区大气中二噁英的季节性监测,结合后向轨迹的计算,对大气中PCDD/Fs的浓度及其长距离迁移来源进行分析.结果表明:大气中二噁英浓度有季节性变化特点,其趋势为冬季(14.4 pg·m^-3)>秋季(10.0 pg·m^-3)>春季(5.54 pg·m^-3)>夏季(3.88 pg·m^-3).同时,大气中PCDD/Fs单体特征也具有季节性特点,秋冬季节七氯代、八氯代PCDD/Fs百分比高于春秋两季,春夏两季低氯代单体百分比含量高于秋冬两季.追溯采样期间该城市大气的后向轨迹,发现秋冬两季到达广州的气团主要经过湖南、湖北和江西等北方或东北方的内陆省份,而春夏两季到达广州的气团主要经过我国东海和南海海域上空.而这种变化很可能是造成广州大气中二噁英浓度季节性变化的主要原因.     

Magnetic compass orientation of migratory birds in the presence of a 1.315 MHz oscillating field

The radical pair model of magnetoreception predicts that magnetic compass orientation can be disrupted by high frequency magnetic fields in the Megahertz range. European robins, Erithacus rubecula, were tested under monochromatic 565 nm green light in 1.315 MHz fields of 0.48 T during spring and autumn migration, with 1.315 MHz being the frequency that matches the energetic splitting induced by the local geomagnetic field. The birds responses depended on the alignment of the oscillating field with respect to the static geomagnetic field: when the 1.315 MHz field was aligned parallel with the field lines, birds significantly preferred northerly directions in spring and southerly directions in autumn. These preferences reflect normal migratory orientation, with the variance slightly increased compared to control tests in the geomagnetic field alone or to tests in a 7.0 MHz field. However, in the 1.315 MHz field aligned at a 24° angle to the field lines, the birds were disoriented in both seasons, indicating that the high frequency field interfered with magnetoreception. These finding are in agreement with theoretical predictions and support the assumption of a radical-pair mechanism underlying the processes mediating magnetic compass information in birds.     

Frequent summer nuptial flights of ants provide a primary food source for bats

In many ant species, nuptial flight tends to be short in time and assumed to be synchronous across a large area. Here, we report that, in the upper Jordan Valley, northern Israel, massive nuptial flights of Carpenter ants (Camponotus sp.) occur frequently throughout the summer, and their alates form up to 90% of the diet of the greater mouse-tailed bat (Rhinopoma microphyllum) during this period. This fat and protein-rich diet enables female bats to lactate during summer, and the large amount of fat that both sexes accumulate may serve as an energy source for their following winter hibernation and posthibernation mating in early spring (March–April). We suggest that the annual movement of these bats to the Mediterranean region of Israel may have evolved in order to enable them to exploit the extremely nutritious forms of ant alates when the bats’ energetic demands are highest.     

三峡库区水体中可溶性C、N变化及影响因素

为了解三峡库区水体中可溶性C、N的变化,本研究于2011年3月至2012年8月在三峡水库涪陵段进行了每周一次的水样采集,分析其中可溶性C、N成分的变化及其来源特征.结果表明,库区水中DOC浓度范围为0.64~9.07 mg·L~(-1),且有明显的季节变化,表现为:夏季春季、秋季冬季,DOC年入库总量为1.78×109kg,入库量具有与浓度相似的季节变化趋势;DTN的浓度范围为2.59~4.35 mg·L~(-1),春季冬季夏季秋季,年入库总量为1.32×109kg,入库量的季节变化特征:夏季秋季春季冬季,其中DON、NO-3-N分别占DTN的30.35%~63.45%、35.87%~67.72%.DOC受降水和温度的影响明显,水中DOC主要来自外源输入,春季、夏季降雨径流其外源输入量增加,而秋季、冬季则内源贡献有所增加;DTN受人为排放和水体稀释的影响相对较大.相关分析表明,DOC与DON呈显著负相关(P0.05),通常以DOC/DON比值反映水中DOM的来源,库区DOC/DON范围为0.35~7.28,DOM来源具有明显的季节特征.夏季DOC/DON较高,DOM主要来自流域侵蚀;冬季DOC/DON较低,DOM主要来自生活污水排放和内源现场产生;春季、秋季DOC/DON介于两者之间,DOM来源包括流域侵蚀、生活污水排放及现场产生等.     

成都市城区大气VOCs季节污染特征及来源解析

为研究成都市城区大气VOCs季节变化特征,本研究在2018年12月至2019年11月对VOCs组分进行监测,并对VOCs的浓度水平、各化学组成、化学反应活性和来源进行分析.结果表明,成都市城区春、夏、秋和冬季VOCs的平均体积分数分别为32.29×10~(-9)、 36.25×10~(-9)、 40.92×10~(-9)和49.48×10~(-9),冬季的浓度明显高于其他季节,春季和夏季的浓度水平相差不大,各季节VOCs的组分浓度水平有所差异,冬季烷烃占总VOCs的比例最大,可能受机动车排放的影响较明显;夏季和秋季含氧(氮)挥发性有机物占比远高于春、冬季,一次源的挥发排放和二次转化的生成贡献较大;成都市城区不同季节大气中VOCs平均浓度排名靠前的关键组分基本无变化,主要是C_2～C_4的烷烃、乙烯、乙炔及二氯甲烷等,可能受机动车尾气、油气挥发、溶剂使用和LPG燃料等影响明显,夏季丙酮以及乙酸乙酯等含氧有机物浓度贡献突出;根据·OH消耗速率和OFP计算可知关键活性物种主要为间/对-二甲苯、乙烯、丙烯、1-己烯、甲苯、异戊烷和正丁烷等,这些物种应该优先减排和控制;四季VOCs源解析结果显示:春、夏季温度较秋、冬季高,光照更强,PMF明显解析出天然源和二次排放贡献,同时,由于夏季温度较高,解析出油气挥发占9%;秋、冬季占比增加的源主要为机动车尾气和燃烧源,燃烧源的排放占比在25%左右,另餐饮源的排放占比在9%左右.     

Magnetoreception in birds: no intensity window in “fixed direction” responses

Under 502 nm turquoise light combined with 590 nm yellow light and in total darkness, European robins, Erithacus rubecula, no longer prefer their migratory direction, but exhibit so-called fixed direction responses that do not show the seasonal change between spring and autumn. We tested robins under these light conditions in the local geomagnetic field of 46 μT, a field of twice this intensity, 92 μT, and a field of three times this intensity, 138 μT. Under all three magnetic conditions, the birds preferred the same easterly direction under turquoise-and-yellow light and the same northwesterly direction under dark, while they were oriented in their seasonally appropriate direction under control conditions. “Fixed direction” responses are thus not limited to a narrow intensity window as has been found for normal compass orientation. This can be attributed to their origin in the magnetite-based receptor in the upper beak, which operates according to fundamentally different principles than the radical pair mechanism in the retina mediating compass orientation. “Fixed direction” responses are possibly a relict of a receptor mechanism that changed its function, now mainly providing information on magnetic intensity.     

氮沉降对缙云山柑橘林不同季节土壤微生物群落结构的影响

土壤微生物积极参与生态系统的物质循环和转化.人类活动造成全球氮沉降量激增,引起土壤微生物群落结构和功能的改变,进而导致生态系统失衡.2014年6月—2015年5月在缙云山柑橘林建立野外模拟氮沉降试验样地,原位设置4个施肥水平:对照(N0,0 g·m~(-2)·a~(-1))(以N计,下同)、低氮(N20,20 g·m~(-2)·a~(-1)),中氮(N4 0,40 g·m~(-2)·a~(-1))和高氮(N60,60 g·m~(-2)·a~(-1)).施氮处理2 d后,采用磷脂脂肪酸(PLFA)标记法和ACE(Automated Soil CO_2Exchange Station,UK)自动土壤呼吸监测系统对土壤微生物群落结构、土壤温湿度进行测定.研究表明:(1)不同季节土壤微生物对氮沉降的响应各异,春季氮沉降抑制土壤微生物量,夏、秋、冬季N40处理提高了土壤微生物量,N20、N60表现为抑制土壤微生物量;氮沉降对土壤温度有显著影响,但对土壤湿度影响不明显(p0.05).(2)土壤微生物丰富度指数和Shannon-Wiener多样性指数在中氮沉降条件下达最大;Pielou均匀度指数则表现不一致,春季和夏季在中氮浓度下最大,秋季在高氮处理下最大,冬季则在低氮处理下最大.(3)土壤温度与放线菌呈显著负相关(p0.01);土壤湿度与细菌和总PLFA呈显著正相关(p0.01),与放线菌呈显著正相关(p0.05).综合分析表明,土壤微生物受土壤温度和含水量的共同影响,氮沉降降低了土壤微生物含量,此研究结果支持了氮沉降抑制土壤微生物的认识.     

辽宁滨海(环渤海)湿地鸟类多样性调查与研究

本研究于2019－2020年对辽宁滨海（环渤海）湿地开展了春迁徙季、秋迁徙季、繁殖季和越冬季的鸟类多样性调查,共监测到鸟类150种,隶属于16目38科,其中,留鸟25种,夏侯鸟26种,冬侯鸟26种,旅鸟73种;国家一级保护鸟类11种,国家二级保护鸟类20种。调查显示:调查区内鸟类多样性的季节差异明显,春、秋迁徙季,鸟类种类与数量明显高于其他两季,越冬季鸟类的种类数量均最少,丰富度指数、均匀度指数、多样性指数和优势度指数均最低。空间分布显示,盘锦地区鸟类种类和数量均最多,达到78种,473084只;营口地区调查到的鸟类种类最少,为55种;锦州地区鸟类数量最少,只有57723只。从鸟类多样性对比来看,盘锦地区最高,大连地区最低,各地鸟类群落组成的空间差异较为明显,在一定程度上受到该地区鸟类生境种类数量及面积大小的影响。辽宁滨海（环渤海）湿地作为东亚—澳大利西亚候鸟迁徙带上的关键区域,当前正面临气候变化、人类围垦干扰造成的鸟类栖息地减少等不利情况,建议通过扩大保护范围、实施修复和管理对策措施、强化宣传等手段保护鸟类多样性及其栖息生境,巩固渤海综合治理攻坚战的治理成效。     

海州湾海洋牧场浮游植物群落结构特征及其与水质参数的关系

为了解海州湾海洋牧场海域浮游植物群落特征,于2013年进行了春(5月)、夏(8月)、秋(10月)3个航次的调查,共鉴定出浮游植物115种,其中,硅藻门种类最多,共97种,占总种数的84.3%,甲藻门次之,共16种,占总种数的13.9%,蓝藻门1种,绿藻门1种.人工鱼礁区各个季节的浮游植物丰度都显著大于对照区(p0.05),而种类数无显著差异(p0.05).人工鱼礁区和对照区的辛普森多样性指数D和香农-威纳指数均在秋季最大,夏季最小,而均匀度J为春季最大,夏季最小.海州湾海洋牧场浮游植物种类数秋季达到36种,丰度在秋季也达到最高为19.68×104cells·m-3,方差分析和聚类分析结果表明,浮游植物群落组成存在显著季节差异(p0.05).应用Canoco5.0软件对获得的浮游植物数据和环境因子数据进行典范对应分析,结果表明,TN、Si O2-3-Si和TP是影响浮游植物群落分布的重要环境因子,其次BOD5和NH+4-N也对浮游植物分布有较大影响.