4. ONE YEAR'S CENSUS AND STUDY OF BIRDS IN 2½ ACRES OF ALEANY BUSHVELD. (Part 2.) April, 1945, to March, 1946

Hooded Vultures Necrosyrtes monachus are critically endangered but little is known of their year-round use of nests or whether other species usurp Hooded Vulture nest sites. We investigated visitation rates by Hooded Vultures and other species (including potential nest predators and usurpers) to examine their effect on Hooded Vulture breeding success. We present observations of 33 species recorded by camera traps at 12 Hooded Vulture nests over a total of 93 nest-months (2 095 nest-days). Several pairs of Hooded Vultures visited their nests regularly during the non-breeding season, some adding nesting material, highlighting that pairs visited their nest(s) year round. Egyptian Geese Alopochen aegyptiaca, potential usurpers of raptor nests, were present at occupied and unoccupied Hooded Vulture nests, but we recorded no usurpation of nests by Egyptian Geese and they had no impact on vulture breeding success. Hooded Vulture breeding failure was linked to two species only: camera-trap imagery recorded one case of predation of a vulture egg by a Chacma Baboon Papio ursinus, and one case of a Martial Eagle Polemaetus bellicosus predating a vulture nestling. We recommend expanding the Hooded Vulture nest monitoring programme to include more pairs.     

秃鹫巢内育雏期亲鸟与幼鸟行为及时间分配

2016和2017年,采用焦点动物取样法及全事件记录法,在新疆和静县巴仑台镇研究了4个繁殖巢的秃鹫(Aegypius monachus)繁殖行为。通过红外相机和人工观察,构建了秃鹫巢内育雏期的行为谱,将秃鹫亲鸟的行为划分为9类33种,将雏鸟行为划分为6类28种。结果表明,亲鸟喂食次数的最高峰出现在12:30～13:30时,随后在15:30～18:30时之间出现一个小高峰。在育雏期,亲鸟行为以护幼、观望和警戒为主,雏鸟则以休息和观望为主。将巢内育雏期分为三个阶段:育雏前期(4～5月)、育雏中期(6月)、育雏后期(7月),运用单因素方差分析(one-way ANOVA)检验不同育雏阶段亲鸟、雏鸟行为时间分配的差异。结果显示,育雏前期与后期之间亲鸟的行为时间分配差异不显著(P>0.05),前期与中期和中期与后期之间,亲鸟的行为时间分配差异均显著(P<0.01);育雏前期、中期与后期的雏鸟行为时间分配差异均显著(P<0.01)。国内秃鹫繁殖主要面临食物短缺、人类活动干扰等威胁。     

Population dynamics of American horseshoe crabs—historic climatic events and recent anthropogenic pressures

Populations of the American horseshoe crab, Limulus polyphemus, have declined, but neither the causes nor the magnitude are fully understood. In order to evaluate historic demography, variation at 12 microsatellite DNA loci surveyed in 1218 L. polyphemus sampled from 28 localities was analysed with Bayesian coalescent‐based methods. The analysis showed strong declines in population sizes throughout the species’ distribution except in the geographically isolated southern‐most population in Mexico, where a strong increase in population size was inferred. Analyses suggested that demographic changes in the core of the distribution occurred in association with the recolonization after the Ice Age and also by anthropogenic effects, such as the past overharvest of the species for fertilizer or the current use of the animals as bait for American eel (Anguilla rostrata) and whelk (Busycon spp.) fisheries. This study highlights the importance of considering both climatic changes and anthropogenic effects in efforts to understand population dynamics—a topic which is highly relevant in the ongoing assessments of the effects of climate change and overharvest.     

Population size and breeding success of the Cinereous Vulture,Aegypius monachus,in a newly found breeding area in western Anatolia (Aves: Falconiformes)

A total of 123 nests of the Cinereous Vulture, Aegypius monachus, was found in three different nesting areas in Middle Sakarya Region, Western Turkey, during three years. The number of breeding pairs was 32 in 2010, 46 in 2011 and 42 in 2012. This is the largest Cinereous Vulture colony in Turkey and the most important breeding area in the western part of its distribution outside Spain. Breeding success was 0.78 fledgling per occupied nest in 2010, 0.73 in 2011 and 0.54 in 2012. The most unsuccessful breeding occurred mostly between May and July, when recreational activities and various economic human activities increased in the area.     

Genetic evidence for high propagule pressure and long‐distance dispersal in monk parakeet (Myiopsitta monachus) invasive populations

The monk parakeet (Myiopsitta monachus) is a successful invasive species that does not exhibit life history traits typically associated with colonizing species (e.g., high reproductive rate or long‐distance dispersal capacity). To investigate this apparent paradox, we examined individual and population genetic patterns of microsatellite loci at one native and two invasive sites. More specifically, we aimed at evaluating the role of propagule pressure, sexual monogamy and long‐distance dispersal in monk parakeet invasion success. Our results indicate little loss of genetic variation at invasive sites relative to the native site. We also found strong evidence for sexual monogamy from patterns of relatedness within sites, and no definite cases of extra‐pair paternity in either the native site sample or the examined invasive site. Taken together, these patterns directly and indirectly suggest that high propagule pressure has contributed to monk parakeet invasion success. In addition, we found evidence for frequent long‐distance dispersal at an invasive site (～100 km) that sharply contrasted with previous estimates of smaller dispersal distance made in the native range (～2 km), suggesting long‐range dispersal also contributes to the species’ spread within the United States. Overall, these results add to a growing body of literature pointing to the important role of propagule pressure in determining, and thus predicting, invasion success, especially for species whose life history traits are not typically associated with invasiveness.     

长江江豚种群衰退机理研究进展

长江江豚（Neophocaena phocaenoides asiaeorientalis）是生活于我国长江中下游的一种独特的淡水小型鲸类,1996年被收录为IUCN濒危物种。在过去的三十年间,其种群数量呈快速下降趋势。数据显示,20世纪90年代以来,其种群下降速率约为每年6.3%。2006年考察发现长江干流中其种群数量少于1 200头,与15年前相比减少了50%以上。为了深入了解造成长江江豚种群快速衰退的机理,课题组从种群生态学、生物声学和种群遗传学三个方面开展研究工作。综述了该项目的研究进展,并对下一步的研究计划进行了展望。相关研究不仅能促进长江江豚保护生物学理论的发展,也有助于深化对白鱀豚衰退和灭绝过程的反思,并为其他长江水生生物资源的保护提供理论借鉴。