麻雀幼鸟和成鸟逃逸距离的比较

逃逸是鸟类常用的反捕食手段。自然选择会优化鸟类的逃逸距离,以便在躲避被捕食风险和保持能量之间做出权衡。理论模型预测动物个体可依据期望寿命来调整自身的行为：期望寿命短的个体倾向于风险偏好,即逃逸距离短;而期望寿命长的个体倾向于风险回避,即逃逸距离长。同时,逃逸距离还受到外部因素（如人为干扰强度、鸟类群体大小）的影响。本研究在北京城区收集了麻雀（Passer montanus）145只成鸟和75只幼鸟的逃逸距离数据,发现麻雀成鸟比幼鸟有着更长的逃逸距离,且成鸟更可能是群体中首先逃逸的个体。此外,研究发现麻雀的逃逸距离随着人为干扰强度的增加而降低,随着群体大小增加而增加。本研究结果符合理论预期：存活率高的类群（成鸟）有着更长的逃逸距离。     

Detecting un-authorized genetically modified organisms (GMOs) and derived materials

Genetically modified plants, in the following referred to as genetically modified organisms or GMOs, have been commercially grown for almost two decades. In 2010 approximately 10% of the total global crop acreage was planted with GMOs (James, 2011). More than 30 countries have been growing commercial GMOs, and many more have performed field trials. Although the majority of commercial GMOs both in terms of acreage and specific events belong to the four species: soybean, maize, cotton and rapeseed, there are another 20 + species where GMOs are commercialized or in the pipeline for commercialization. The number of GMOs cultivated in field trials or for commercial production has constantly increased during this time period. So have the number of species, the number of countries involved, the diversity of novel (added) genetic elements and the global trade. All of these factors contribute to the increasing complexity of detecting and correctly identifying GMO derived material. Many jurisdictions, including the European Union (EU), legally distinguish between authorized (and therefore legal) and un-authorized (and therefore illegal) GMOs. Information about the developments, field trials, authorizations, cultivation, trade and observations made in the official GMO control laboratories in different countries around the world is often limited, despite several attempts such as the OECD BioTrack for voluntary dissemination of data. This lack of information inevitably makes it challenging to detect and identify GMOs, especially the un-authorized GMOs. The present paper reviews the state of the art technologies and approaches in light of coverage, practicability, sensitivity and limitations. Emphasis is put on exemplifying practical detection of un-authorized GMOs. Although this paper has a European (EU) bias when examples are given, the contents have global relevance.     

Changes in vegetation phenology are not reflected in atmospheric CO2 and 13C/12C seasonality

Northern terrestrial ecosystems have shown global warming‐induced advances in start, delays in end, and thus increased lengths of growing season and gross photosynthesis in recent decades. The tradeoffs between seasonal dynamics of two opposing fluxes, CO₂ uptake through photosynthesis and release through respiration, determine the influence of the terrestrial ecosystem on the atmospheric CO₂ and ¹³C/¹²C seasonality. Here, we use four CO₂ observation stations in the Northern Hemisphere, namely Alert, La Jolla, Point Barrow, and Mauna Loa Observatory, to determine how changes in vegetation productivity and phenology, respiration, and air temperature affect both the atmospheric CO₂ and ¹³C/¹²C seasonality. Since the 1960s, the only significant long‐term trend of CO₂ and ¹³C/¹²C seasonality was observed at the northern most station, Alert, where the spring CO₂ drawdown dates advanced by 0.65 ± 0.55 days yr^?1, contributing to a nonsignificant increase in length of the CO₂ uptake period (0.74 ± 0.67 days yr^?1). For Point Barrow station, vegetation phenology changes in well‐watered ecosystems such as the Canadian and western Siberian wetlands contributed the most to ¹³C/¹²C seasonality while the CO₂ seasonality was primarily linked to nontree vegetation. Our results indicate significant increase in the Northern Hemisphere soil respiration. This means, increased respiration of ¹³C depleted plant materials cancels out the ¹²C gain from enhanced vegetation activities during the start and end of growing season. These findings suggest therefore that parallel warming‐induced increases both in photosynthesis and respiration contribute to the long‐term stability of CO₂ and ¹³C/¹²C seasonality under changing climate and vegetation activity. The summer photosynthesis and the soil respiration in the dormant seasons have become more vigorous which lead to increased peak‐to‐through CO₂ amplitude. As the relative magnitude of the increased photosynthesis in summer months is more than the increased respiration in dormant months, we have the increased overall carbon uptake rates in the northern ecosystems.     

羚牛防御行为的观察

1995年8月到1996年8月对陕西佛坪自然保护区境内的72群次羚牛(独牛31只次, 羚牛群41次) 的防御行为进行了观察。羚牛的防御行为包括发现、警觉、示警、御敌4种方式。羚牛通过视觉、嗅觉和听觉发现异常情况, 但其听觉更为敏锐。羚牛十分警觉, 稍有异常就会进入警觉状态, 警觉行为持续的时间为18.26±18.08 s。所有的羚牛个体均能通过声音和动作向同伴进行示警, 但3龄以下的个体发出的示警行为往往不能得到重视。御敌行为包括聚集、威吓、护幼、攻击、逃跑。逃跑是羚牛躲避敌害的主要手段, 在72群次中逃跑的羚牛占95.8%。羚牛逃跑时往往进行长距离的迁移并具有分群的现象, 但仍会返回原地。群体的大小对羚牛的分群行为有影响, 群体越大, 分群逃跑的可能性也越大。羚牛具有明显的护幼行为, 当群体中有幼仔时羚牛的攻击性增大。独牛攻击人的可能性要比群牛大。     

Ventilatory frequency of Nile tilapia subjected to different stressors

Ventilatory frequency (VF) was investigated in the fish Nile tilapia, Oreochromis niloticus, subjected to confinement, electroshock or social stressor. Fish were allowed to acclimatize to tank conditions for 10 days (1 fish/aquarium). VF baseline was determined 5 days after adjustment had been started. At the 10th day of isolation, stressor effects on VF were assessed. The stressors were imposed during 60 min: pairing with a larger resident animal (social stressor), or gentle electroshock (AC, 20 V, 15 mA, 100 Hz for 1 min every 4 min), or space restriction (confinement). VF was quantified immediately after the end of the stressor imposition. Baseline of VF was not statistically different among groups. Social stressor clearly induced VF to increase, while an increased or decreased VF can be observed for both confinement and electroshock. However, fish tend to increase their VF in response to confinement and decrease in the case of electroshock. These results suggest that VF is a sensitive behavioural indicator for distinguishing stress responses in the fish Nile tilapia among different stressors.     

The effectiveness of bird hides in mitigating recreational disturbances of birdwatchers

Bird hides are often built to ameliorate the disturbance of birdwatchers at birdwatching sites. However, the effectiveness of such shelters is rarely evaluated. This study investigated the recreational disturbances induced by birdwatchers at Mai Po Nature Reserve in Hong Kong and examined the effectiveness of bird hides in mitigating birdwatcher impacts. A bird disturbance survey was conducted to record the disturbances caused by birdwatchers and responses shown by birds at three sampling sites in Mai Po Nature Reserve. A total of 469 observations were recorded in 25 field days from Oct 2019 to April 2020. The results indicated that bird hides significantly mitigated the frequency of disturbance and level of response of birds. With a bird hide, the frequency of disturbance was lower than the unsheltered site given that both sites have a similar level of visitation, yet, disturbance frequency was not significantly lower if the bird hide was highly utilized by birdwatchers. Birds had shown less vigorous and slower responses to disturbances at sites with bird hides than that without. On the other hand, at those sites with bird hides, birds responded at a farther distance than birds at the unsheltered site, which a longer distance may represent a greater level of disturbance. Upon disturbances, birds at the unsheltered site tended to stay in the original area, while birds around bird hides tend to settle further from the original habitat. Visual disturbances were well avoided at bird hides when compared to an unsheltered environment, however, disturbance from noise was found to be more prevalent at bird hides. Implications of these findings were discussed, and recommendations regarding the use, setting, and design of bird hides, and visitor management were given.