骨顶鸡日行为活动对游憩干扰的反应

近年来,湿地生态旅游在我国各地逐渐兴起,水鸟作为湿地生态系统的重要成分,其行为是否因游憩活动而改变成为了重要的研究内容。本文以黑龙江省安邦河自然保护区为研究区,调查了骨顶鸡(Fulica atra)对湿地游憩活动的行为反应,用瞬时扫描取样法分别观察了码头区、游船区和对照区骨顶鸡成鸟及幼鸟的日行为活动。结果表明,码头区成鸟比对照区取食时间显著减少,隐藏的时间明显增加,游走和整理活动显著降低;游船区成鸟比对照区出现更多的攻击和隐藏行为。游憩区幼鸟与对照区的取食、隐藏和躲避时间有显著差异。游憩干扰还表现在码头区成鸟的取食节律片段化,成鸟和幼鸟隐藏频率较高的时段与游人的活动高峰相一致。研究认为,游船区干扰对骨顶鸡的影响较码头区小,幼鸟比成鸟对干扰的适应能力更强。由于高强度的游憩干扰对骨顶鸡等水鸟种群秋迁前的能量蓄积不利,因此建议增加码头路边隔离绿化带,在游船与骨顶鸡领域间设置浮标隔离带,加强对游憩活动的管理。     

斑块生境中食果鸟类对南方红豆杉种子的取食和传播

生境斑块化对食果鸟类的移动行为产生影响,进而影响其对植物种子的传播格局和效率。南方红豆杉(Taxus chinensis var.mairei)是我国一级保护植物,在南方山区多因人为干扰而呈斑块状分布。2011年,2012年10月底到12月中,以分布于福建梅花山国家级自然保护区红豆杉生态园中南方红豆杉种群为对象,研究斑块生境中鸟类对南方红豆杉种子的取食和传播行为,并评估专性鸟类和泛性鸟类的传播效率。结果发现:南方红豆杉源斑块共吸引22种食果鸟类取食红豆杉种子,并与13种鸟类形成了种子传播关系。不同年间,黑短脚鹎(Hypsipetes leucocephalus)都是植物的主要传播鸟类,而其他鸟类传播者种类具有一定的年间变化。生境斑块化导致专性鸟类黑短脚鹎和泛性鸟类红嘴蓝鹊(Urocissa erythrorhyncha)种子传播效率差异。与红嘴蓝鹊相比,黑短脚鹎飞行的平均距离较短((16.3±11.0)m,Mean±SD,n=125),传播距离相对较近;且它们取食后偏好在源斑块中活动,喜栖息在同种成树、甜楮(Castanopsis eyrei)及其他阔叶树等栖树上。红嘴蓝鹊取食后常在斑块间移动,常停歇在同种成树和毛竹(Phyllostachys heterocycla)上,传播距离相对较远((24.9±20.0)m,Mean±SD,n=95)。空间一致性结果表明,黑短脚鹎移动距离对幼苗更新距离的空间一致性程度高;而红嘴蓝鹊偏好生境与幼苗更新生境一致性程度高。结果表明,斑块生境中植物能与专性鸟类、泛性鸟类之间形成种子传播互惠关系,且种子传播效率受到专性鸟类和泛性鸟类传播距离和传播生境的影响。     

金秀大瑶山瑶民“鸟盆”狩猎区鸟类食物源植物及生态保育

2003年7月～2008年12月,对金秀大瑶山茶山瑶民"鸟盆"狩猎活动区域的鸟类食物源植物进行了调查,录得"鸟盆"狩猎区秋冬季鸟类取食果实、种子的植物有28科71种,当地称为"鸟果"树。此外,瑶民"鸟盆"狩猎活动所需的"鸟漆"(粘捕鸟类的粘胶)是用9种冬青科植物的树皮制作,其果实、种子亦是"鸟盆"狩猎活动区鸟类的主要食物。     

食果鸟类对红楠种子的传播作用

肉质果植物通常依赖食果鸟类等取食果实后经消化道过程传播种子, 以完成种群的更新。红楠(Machilus thunbergii)是亚热带森林的代表性种类, 其果实具有依赖鸟类等动物取食后传播的特点。2012 年、2013 年在梅花山国家级自然保护区,研究了鸟类对红楠果实的取食及种子的传播作用。结果如下: 取食红楠种实的鸟类共计18 种, 其中整吞果实的鸟类12 种,啄取果肉的鸟类5 种, 啄食种子的鸟类1 种。整吞果实鸟类中4 种鹎科和2 种鸦科鸟类访问频次和取食量较大, 是主要的种子传播者。鸟类主要以呕吐方式传播种子。取食后初停栖点与母树距离及地面种子散布地点的分析结果表明, 鸟类可以远距离扩散种子。地面种实可被啮齿动物或蚁类再次捕食或搬运。研究表明, 红楠可以借助鸟类实现种子传播和种群更新。     

南京中山植物园鸟类对香樟 果实（种子）的取食

香樟(Cinnamomum camphora)是亚热带地区广泛分布的常绿阔叶树种,其果实数量多、果期长,可为鸟类提供大量食物资源。2018年11月至2019年2月,借助Safari 10×26变焦双筒望远镜,采用焦点扫描法对南京中山植物园内访问香樟果实(种子)的鸟类行为进行观察,详细记录鸟类的种类、取食基质、取食次数、取食时间、取食数量和取食方式等信息。研究期间有效记录达48d,累计记录到27种鸟类1021次取食香樟果实(种子)行为,存在2种取食基质(地面和树上)和3种取食方式(整吞果实、啄食果肉和取食种子)。T检验显示,不同鸟类对香樟果实(种子)的取食次数存在显著差异(t=3.096,df=26,P 0.01);不同月份间鸟类对香樟香樟果实(种子)的平均访问只数、平均取食次数、平均取食时间和取食数量均存在极显著差异(P0.001)。白头鹎(Pycnonotussinensis)、乌鸫(Turdusmendarinus)和灰喜鹊(Cyanopicacyanus)是访问次数及取食量最多的3种鸟类。单因素方差分析(One-way ANOVA)表明,上述这3种鸟类的取食数量存在极显著差异(F3, 598=25.219,P 0.001)。按照时间统计,11月份访问的鸟类种类和数量最多,1月份鸟类的取食次数、时间和数量最多。鸟类的形态特征(体重、体长和嘴峰长)与取食数量呈显著正相关,其中,体重和体长对取食数量的影响比嘴峰长的影响更显著,但嘴峰长影响鸟类对果实的取食方式。在鸟类常活动和停歇的树木下方地面往往散落着较多表面洁净、无果肉包裹的香樟种子,且园内人工林和自然更新林地可见许多香樟幼苗,表明鸟类对香樟具有潜在传播作用。     

安邦河自然保护区繁殖期骨顶鸡对游憩干扰的行为反应

随着湿地生态旅游的发展,水禽面临着越来越多的游憩干扰。骨顶鸡在我国北方大部分地区的湖泡沼泽繁殖,可作为湿地质量的指示物种,探讨该物种对游憩干扰的反应很有意义。在黑龙江省安邦河自然保护区的游憩区和对照区进行了繁殖期骨顶鸡日行为观察,比较分析结果显示:繁殖前期游憩区骨顶鸡的躲避行为显著高于对照区(F_(1,18)=62.364,P0.01);孵卵期骨顶鸡对游憩干扰的反应比繁殖前期更强烈,除了躲避行为显著增加(雄性F_(1,8)=40.653,P0.01;雌性F_(1,8)=32.028,P0.01),还主要表现在雌骨顶鸡孵卵时间减少(F_(1,8)=13.521,P0.01),持续孵卵时间缩短;雄骨顶鸡取食时间峰值增加,取食中断不连续;雌雄骨顶鸡繁殖期行为及对游憩干扰反应有所不同。建议通过改善游憩区的隐蔽条件,以提供躲避空间,提高生境质量,减少游憩干扰的影响。     

围垦堤内迁徙(行鸟)鹬群落的生态学特性

以群落生态学的原理为基础,研究景观特征及异质性变化导致鸟类群落的变化,重点探讨了人为干扰导致的景观特征变化对迁徙(行鸟)鹬群落时空结构的影响.景观异质性的改变是引起(行鸟)鹬群落结构变化的主要原因,也是决定(行鸟)鹬群落分布的重要因子.围堤内湿地植被覆盖率大于60%或水面小于总湿地面积20%后,(行鸟)鹬基本不出现,必须含有水域、植被和裸地三种景观要素.植被覆盖率为10%～20%时,(行鸟)鹬数量最多.(行鸟)鹬在围堤内滩涂的分布与底栖生物量无关.水深是影响(行鸟)鹬分布的重要因素,使(行鸟)鹬的空间生态位得到分离.(行鸟)科鸟类主要活动在裸地和浅水区,中小型鹬类主要在中水区,大中型鹬类在深水区.科学管理围堤封堵后滩涂,控制和改造湿地景观,将在一定程度上降低围涂工程对(行鸟)鹬群落的负面效应.     

城市绿地中鸟类对海南蒲桃的取食和传播作用

海南蒲桃(Syzygium cumini)是亚热带地区城市绿地中常见的绿化植物, 其果实数量多、果期长, 可为鸟类提供大量食物资源。2020年6月—8月借助 Safari 10×26 变焦双筒望远镜, 采用焦点扫描法对访问海南蒲桃果实(种子)的鸟类行为进行观察, 详细记录鸟类的种类、取食基质、访问频次、取食时间、取食数量和取食方式等信息, 探讨鸟类在海南蒲桃种子传播及种群更新中的生态作用。结果表明: 成熟的海南蒲桃能吸引7种食果鸟类对其种子进行取食,其中白头鹎(Pycnonotus sinensis)、红耳鹎(Pycnonotus jocosus)、白喉红臀鹎(Pycnonotus aurigaster)和黄臀鹎(Pycnonotus xanthorrhous)4种鸟类以整吞的方式取食海南蒲桃的种子, 属于种子潜在传播者。不同种鸟类对海南蒲桃果实的取食频次间存在显著差异(t=4.310, df=6, P < 0.01), 平均访问只数、平均取食时间和平均取食量间存在极显著差异(P < 0.001)。食果鸟类的形态特征(体长、体重和嘴峰大小)与取食数量间均呈正相关。鸟类主要以呕吐的方式传播海南蒲桃的种子, 观察期间在鸟类取食后停歇的树木下方地面上常散落着较多表面洁净、无果肉包裹的裸露种子, 且有大量的海南蒲桃幼苗成功更新, 说明城市绿地中的植物是可以借助鸟类的取食和传播来实现其种群的更新。     

食果鸟类在红豆杉天然种群形成中的作用

2005年10月初至2006年2月,在南京中山植物园研究了红豆杉(Taxus chinensis)天然更新种群的分布格局,野外定点观察了鸟类对红豆杉种子的取食行为,记录了红豆杉落果的命运,分析了食果鸟类在红豆杉种群形成中的作用。结果表明:红豆杉天然更新种群集中分布于距母树群10m以外面积约0.5hm2的山坡上,全部红豆杉幼苗、幼树共213株,主要分布在中下坡;幼苗和幼树的空间水平格局符合聚集分布特征。"果实"成熟后,一部分被鸟类直接在树上取食,一部分掉落母树下地面。经过对结实母树的定点、连续观察,记录到4种鸟类取食红豆杉"果实",其中红嘴蓝鹊(Urocissa erythrorhyncha)和白头鹎(Pyc-nonotus sinensis)为主要的取食者和传播者。食果鸟类整吞"果实",消化果肉(假种皮)后,种子经消化道随粪便排出,以此过程传播种子。在取食完红豆杉"果实"后,食果鸟类多飞向坡上。坡上排水良好,有适量的荫蔽,生境适宜红豆杉种子萌发和幼苗的成长。因此,食果鸟类将种子传播至适宜萌发和生长的环境中,对该红豆杉种群的天然更新起主要作用。同时,鸟类传播对于红豆杉种群扩散、占据新的生境也有着特殊的意义。     

福建梅花山自然保护区鸟类种子传播网络

鸟类与植物的种子传播网络是影响生物多样性维系和生态系统功能的关键因素,同时也是当代生态学研究的热点。于2021年10—12月采用样线法在福建梅花山国家级自然保护区南部地区调查取食鸟类多样性,并分析其与植物特征之间的关系,收集鸟类对果实(种子)的取食数据并以此构建鸟类种子传播网络,探讨鸟类特征对网络结构的影响。结果表明：取食鸟类多样性与植物特征之间存在一定相关性,取食鸟类种类、数量、均匀度指数与植物高度、结实量和郁闭度呈显著相关(P<0.05);种子传播网络由21种取食鸟类和15种植物构成,具有嵌套性和模块性,但连接度和专业化程度较低;鸟类特征与物种水平网络参数存在一定相关性,取食鸟类数量与取食鸟类物种度、物种强度和连接多样性均呈极显著正相关(P<0.01),取食鸟类体重、体长、嘴峰长与取食鸟类物种度和连接多样性呈显著正相关(P<0.05)。研究显示,鸟类特征对种子传播网络结构的构建和维持具有影响,研究结果为分析森林动植物关系的动态变化和稳定性提供现实参考。     

Seed dispersal of a fleshy-fruited invasive shrub is affected by changes in the frugivorous bird assemblage along an elevational gradient

Seed dispersal by birds constitutes an essential mechanism for ornithochorous exotic plants to successfully invade a new system. New biotic associations with native birds might facilitate the upward spread of exotic plants from the foothills into the high mountains. However, environmental changes associated with elevation are known to drive changes in bird assemblages, and it is not clear how elevation changes impact the seed dispersal service of ornithochorous invaders. We evaluated changes in frugivorous bird assemblages of one of the exotic shrubs (Cotoneaster franchetii, Rosaceae) with the broadest elevation range among woody invaders in the Córdoba Mountains (Argentina). We quantified frugivory interactions (including absolute and proportional fruit consumption by seed dispersers, pulp consumers, and seed predators) using 4-h observations of focal C. franchetii shrubs distributed across low-elevation, mid-elevation, and high-elevation sites (700, 1100, and 1800 m a.s.l., respectively; 15 individuals per elevational band and one site per elevation). Seed disperser richness was highest at the low- and mid-elevation sites (three species vs. one at the high-elevation site), but proportional and absolute fruit consumption of C. franchetii was highest at the high-elevation site (39.1%, 88 seeds at high-elevation and 7.7%, 20 seeds at low-elevation). The Chiguanco Thrush (Turdus chiguanco, Turdidae) was the only seed disperser species found at the highest elevation site. Fruit consumption by seed dispersers was positively related to their abundance and elevation. In a high mountain system, a single abundant generalist seed disperser, rather than a high richness of seed disperser species, can uphold an effective dispersal service for an invasive ornithochorous shrub. This pattern may facilitate the spread of such plants across higher elevational ranges, thereby promoting the invasion of other exotic ornithochorous plants into upper elevations.     

Behavioral Responses of North American Elk to Recreational Activity

ABSTRACT Off-road recreation on public lands in North America has increased dramatically in recent years. Wild ungulates are sensitive to human activities, but the effect of off-road recreation, both motorized and nonmotorized, is poorly understood. We measured responses of elk (Cervus elaphus) to recreational disturbance in northeast Oregon, USA, from April to October, 2003 and 2004. We subjected elk to 4 types of recreational disturbance: all-terrain vehicle (ATV) riding, mountain biking, hiking, and horseback riding. Motion sensors inside radiocollars worn by 13 female elk recorded resting, feeding, and travel activities at 5-minute intervals throughout disturbance and control periods. Elk fed and rested during control periods, with little time spent traveling. Travel time increased in response to all 4 disturbances and was highest in mornings. Elk travel time was highest during ATV exposure, followed by exposure to mountain biking, hiking, and horseback riding. Feeding time decreased during ATV exposure and resting decreased when we subjected elk to mountain biking and hiking disturbance in 2003. Our results demonstrated that activities of elk can be substantially affected by off-road recreation. Mitigating these effects may be appropriate where elk are a management priority. Balancing management of species like elk with off-road recreation will become increasingly important as off-road recreational uses continue to increase on public lands in North America.     

Frugivory,Post‐feeding Flights of Frugivorous Birds and the Movement of Seeds in a Brazilian Fragmented Landscape

Habitat fragmentation can break down the movement processes of frugivorous animals, thus influencing the relationship between plants and their seed dispersers by altering the number and identity of seed dispersers, and their relative contribution to seed dispersal. We studied the assemblages of frugivorous birds, their composition, species richness, and visitation rates to fruiting plants growing in the different landscape elements (forest fragments, live fences, and trees isolated in pastures) embedded in a Brazilian fragmented, agricultural landscape. By following the post‐feeding movements of frugivorous birds, we inferred the direction of seed movement from and to each of these landscape elements. Fruiting trees growing at different landscape elements were visited by frugivorous birds at similar rates. Isolated trees attracted a greater and distinct bird assemblage than trees in forest fragments or live fences. Judging by the post‐feeding flights of birds, the seeds of isolated trees were the most likely to reach all the landscape elements considered, but the contribution of isolated trees to the seeds falling in forested habitats or pastures depended on their degree of isolation. A few bird species were able to move widely, visiting fruiting plants in all landscape elements, and promoting long‐distance dispersal for plants. These few birds are of special interest because they are mobile links that connect habitats in fragmented landscapes with their seed dispersal services. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

Exclusive frugivory and seed dispersal of Rhamnus alaternus in the bird breeding season

We studied avian frugivory and seed dispersal in a dioecious shrub, Rhamnus alaternus, focusing on the quantitative and qualitative components of effectiveness. The study took place at three locations in the northeast of the Iberian Peninsula, and examined bird behaviour, intensity of feeding, and the consequences for seedling emergence. The coincidence between the bird breeding season and fruit ripening of R. alaternus in the absence of other ripe fruit, generates a monospecific interaction. The extant frugivorous species were mainly legitimate seed dispersers and their abundance was low. Sylvia melanocephala and S. undata were the most important at one site whereas S. atricapilla, Erithacus rubecula and Turdus merula predominated at the other two sites. Fruit handling took place directly on the branches. Bird species used microhabitats differently as first post-feeding perch, which usually was a short distance away. The low density of frugivorous birds in all localities, among others factors, resulted in satiation of the disperser community and many mature fruits unconsumed. Both adults and juveniles feed upon the plants and their foraging patterns are similar. Adults of S. melanocephala were observed to feed fruit to nestlings and consequently a second phase of dispersal potentially arises from the transport of fecal sacs. Pulp removal and passage through the digestive tract increased the probability of seedling emergence. This plant-dispersal interaction has important consequences, both positive and negative for the plant. Positively, the fruiting of R. alaternus at a time when other ripe fruits are not available avoids interspecific competition for seed dispersers. In addition, a low density of seed rain may reduce intraspecific competition. Negatively, the low density and small size of the breeding frugivorous bird community limit fruit handling and removal away from the parent plants, while the territorial behaviour of birds at that time of the year reduces the potential distances of seed dispersal.     

Feeding Behavior of Purple‐throated Fruitcrow (Querula purpurata: Cotingidae) in the Colombian Amazon and Its Implications for Seed Dispersal1

We studied some feeding behaviors of the purple‐throated fruitcrow (Querula purpurata) in two Colombian Amazonian forests, which affect the primary seed dispersal of the plants on which it feeds. Visit length, number of fruits removed and dispersed, feeding rates, and fruit‐handling times were compared to those obtained for two other cotingas feeding on the same fruiting trees. Querula purpurata exhibited shorter visits (98 sec) and fruit‐handling times (4 sec), and higher mean feeding rates (1.6 fruits/min) than Phoenicircus nigricollis and Cotinga cayana. In contrast, P. nigricollis dispersed the highest number of seeds of four of the five tree species studied. Although Q. purpurata and P. nigricollis exhibited feeding behaviors that increase seed dispersal, Q. purpurata may be more important in the transport of seeds between habitats, while P. nigricollis may be a major seed disperser within the primary forest.     

Functional variation among frugivorous birds: implications for rainforest seed dispersal in a fragmented subtropical landscape

Seed dispersal plays a critical role in rainforest regeneration patterns, hence loss of avian seed dispersers in fragmented landscapes may disrupt forest regeneration dynamics. To predict whether or not a plant will be dispersed in fragmented forests, it is necessary to have information about frugivorous bird distribution and dietary composition. However, specific dietary information for frugivorous birds is often limited. In such cases, information on the seed-crushing behaviour, gape width and relative dietary dominance by fruit may be used to describe functional groups of bird species with respect to their potential to disperse similar seeds. We used this information to assess differences in the seed dispersal potential of frugivorous bird assemblages in a fragmented rainforest landscape of southeast Queensland, Australia. The relative abundance of frugivorous birds was surveyed in extensive, remnant and regrowth rainforest sites (16 replicates of each). Large-gaped birds with mixed diets and medium-gaped birds with fruit-dominated diets were usually less abundant in remnants and regrowth than in continuous forest. Small-gaped birds with mixed diets and birds with fruit as a minor dietary component were most abundant in regrowth. We recorded a similar number of seed-crushing birds and large-gaped birds with fruit-dominated diets across site types. Bird species that may have the greatest potential to disperse a large volume and wide variety of plants, including large-seeded plants, tended to be less abundant outside of extensive forests, although one species, the figbird Sphecotheres viridis, was much more abundant in these areas. The results suggest that the dispersal of certain plant taxa would be limited in this fragmented landscape, although the potential for the dispersal of large-seeded plants may remain, despite the loss of several large-gaped disperser species.     

干扰对动物传播森林植物种子有效性影响的研究进展

干扰在森林生态系统中普遍存在,并影响森林的更新和演替.动物传播种子是种子更新的必经阶段,其对森林干扰的响应在一定程度上能够预测未来的森林群落组成和结构变化,对于明确森林演替方向具有重要意义.本文论述了森林干扰对动物传播种子有效性(包括动物传播种子的数量和质量)影响研究的生态学意义,全面揭示了自然干扰(火干扰、林窗干扰等)和人为干扰(生境破碎化、狩猎、采伐等)对动物传播种子数量、传播距离以及传播后幼苗更新影响的研究进展,指出干扰通过影响动物种群动态,进而造成动物传播种子数量发生了改变,动物传播种子的距离对干扰的响应基本表现出轻微负相关;干扰对传播后幼苗更新的影响结果因干扰类型的不同而复杂多变,干扰迹地环境因子的变化也影响着传播后的种子萌发和幼苗更新.干扰对动物传播种子有效性影响研究中存在的问题,主要表现为火干扰迹地恢复过程、增益性的干扰(如抚育、间伐、林窗)等对种子传播有效性影响研究的匮乏,以及忽略了温带森林内的干扰对动物传播种子的影响等.今后,应开展干扰对种子传播有效性的长期研究;对于干扰多发地带的森林,应高度重视增益性干扰影响动物传播植物种子的研究.     

Diversity of seeds captured by interception exceeds diversity of seeds deposited in traps

Seed dispersal, a key process in terrestrial landscapes, is increasingly important in the face of habitat fragmentation and global climate change. Seed dispersal is also notoriously difficult to characterize, especially in species rich and spatially complex tropical forests. We contrasted assemblages of biotically dispersed seeds collected from four sites using two methods: deposition into seed traps and interception by the capture of frugivorous birds. We also compared seed deposition and interception with local fruit production. Species accumulation curves for seeds deposited in seed traps began to level off sooner than curves for seeds collected from birds captured in mist nets, and extrapolation showed significantly greater estimated species richness for seeds collected from birds than for those deposited in traps. Assemblages from birds and from traps at each site were quite different, with an abundance‐based similarity index of 0.64; this dissimilarity increases if bat‐dispersed seeds are included in the analysis. Common bird‐dispersed species were retrieved from both mist‐netted birds and from seed traps, but numerous locally fruiting understory species were recovered only from birds. We conclude that the sampling of seeds carried by birds provides a valuable complement to other methods of studying seed dispersal in species‐rich tropical forests by revealing relationships between specific dispersers and their seed plants and by creating a more complete account of species diversity of seeds being transported at a given site.     

An invasive tree alters the structure of seed dispersal networks between birds and plants in French Polynesia

Aim We studied how the abundance of the highly invasive fruit‐bearing tree Miconia calvescens DC. influences seed dispersal networks and the foraging patterns of three avian frugivores. Location Tahiti and Moorea, French Polynesia. Methods Our study was conducted at six sites which vary in the abundance of M. calvescens. We used dietary data from three frugivores (two introduced, one endemic) to determine whether patterns of fruit consumption are related to invasive tree abundance. We constructed seed dispersal networks for each island to evaluate how patterns of interaction between frugivores and plants shift at highly invaded sites. Results Two frugivores increased consumption of M. calvescens fruit at highly invaded sites and decreased consumption of other dietary items. The endemic fruit dove, Ptilinopus purpuratus, consumed more native fruit than either of the two introduced frugivores (the red‐vented bulbul, Pycnonotus cafer, and the silvereye, Zosterops lateralis), and introduced frugivores showed a low potential to act as dispersers of native plants. Network patterns on the highly invaded island of Tahiti were dominated by introduced plants and birds, which were responsible for the majority of plant–frugivore interactions. Main conclusions Shifts in the diet of introduced birds, coupled with reduced populations of endemic frugivores, caused differences in properties of the seed dispersal network on the island of Tahiti compared to the less invaded island of Moorea. These results demonstrate that the presence of invasive fruit‐bearing plants and introduced frugivores can alter seed dispersal networks, and that the patterns of alteration depend both on the frugivore community and on the relative abundance of available fruit.     

Are tortoises important seed dispersers in Amazonian forests?

According to most studies on seed dispersal in tropical forests, mammals and birds are considered the main dispersal agents and the role played by other animal groups remains poorly explored. We investigate qualitative and quantitative components of the role played by the tortoise Chelonoidis denticulata in seed dispersal in southeastern Amazon, and the influence of seasonal variation in tortoise movement patterns on resulting seed shadows. Seed shadows produced by this tortoise were estimated by combining information on seed passage times through their digestive tract, which varied from 3 to 17 days, with a robust dataset on movements obtained from 18 adult C. denticulata monitored with radio transmitters and spoon-and-line tracking devices. A total of 4,206 seeds were found in 94 collected feces, belonging to 50 seed morphotypes of, at least, 25 plant genera. Very low rates of damage to the external structure of the ingested seeds were observed. Additionally, results of germination trials suggested that passage of seeds through C. denticulata’s digestive tract does not seem to negatively affect seed germination. The estimated seed shadows are likely to contribute significantly to the dispersal of seeds away from parent plants. During the dry season seeds were dispersed, on average, 174.1 m away from the location of fruit ingestion; during the rainy season, this mean dispersal distance increased to 276.7 m. Our results suggest that C. denticulata plays an important role in seed dispersal in Amazonian forests and highlight the influence of seasonal changes in movements on the resulting seed shadows.