骨顶鸡的繁殖行为

2008和2009年4-9月,对黑龙江省安邦河自然保护区以及龙凤湿地骨顶鸡繁殖种群进行了观察.结果表明:骨顶鸡繁殖季节会建造3种巢结构:炫耀台、产卵巢和育雏巢,雌雄共同参与筑巢及领域防卫活动;巢高和巢深随窝卵数增多而呈上升趋势;平均窝卵数为8.77±0.24(n=75)枚,窝卵数随繁殖时间推迟而呈减少趋势;骨顶鸡雌雄共同参与孵化,雌性平均每次孵化时间高于雄性;雌雄共同参与喂雏,雏鸟至亚体阶段才完全独立,之前需亲鸟饲喂;骨顶鸡是杂食性鸟类,食物以植物为主,但也摄取动物性食物.     

若尔盖湿地骨顶鸡的繁殖生态及适应性探讨

本文研究了四川省若尔盖湿地骨顶鸡Fulica atra的繁殖生态,讨论了骨顶鸡繁殖特征对高原的适应性。结果表明:若尔盖骨顶鸡平均筑巢期为6.73 d±0.36 d,平均巢底距水面距离平均为7.83 cm±0.64 cm,未发现对旧巢重复利用的现象;平均窝卵数5.83枚±2.15枚,平均卵质量31.90 g±0.37 g,平均孵卵时间26.64 d±2.83 d。与低海拔平原湿地相比,高寒湿地繁殖的骨顶鸡窝卵数更少、孵化期更长,并偏好在植被盖度适中、紧邻植被且草高较高的生境中营巢。主成分分析结果显示,影响研究区域骨顶鸡巢址选择的主要因子是安全因子,其次是交通因子与种内竞争因子。与平原地区繁殖的骨顶鸡相比,若尔盖地区骨顶鸡在繁殖生态特征上呈现出对安全因子高度偏好的特点,可能是其对高原多变气候环境和较高捕食压力的一种适应和选择策略。     

大杜鹃在荒漠伯劳巢中寄生繁殖

2010年5～7月在安西极旱荒漠国家级自然保护区发现3巢荒漠伯劳被大杜鹃寄生,寄生率10.34%.荒漠伯劳产白色和粉红色两种颜色的卵,大杜鹃产白色寄生卵于卵色为白色的宿主巢中.寄生卵均产于6月,当月寄生率达42.86%.大杜鹃雏鸟19日龄离巢,离巢时体重66.24 g.     

两种潜鸭不完全巢寄生行为

人们在对美洲潜鸭(Aythya americana)的研究中发现:尽管美洲潜鸭自行筑巢产卵繁殖,但也常常将卵产于其它鸭类的巢中,使之代为孵卵育雏,这种现象被称之为不完全的巢寄生行为。红头潜鸭(Aythya ferina),青头潜鸭(Aythya baeri)和美洲潜鸭同属雁形目鸭科潜鸭属,繁殖于我国的红头潜鸭和青头潜鸭是否和美洲潜鸭一样也具有不完全的巢寄生行为,未见报道。作者于1988年全年及1989年上半年在向海国家级自然保护区进行了观察,发现在向海繁殖的红头潜鸭和青头潜鸭均具有不完全的巢寄生行为。巢寄生分为种间巢寄生和种内巢寄生两类。 种间巢寄生共发现16巢,见表1和表2。     

鹰鹃对白腹短翅鸲的巢寄生

2015年4~8月,在贵州宽阔水国家级自然保护区,记录到1巢白腹短翅鸲(Hodgsonius phaenicuroides)被鹰鹃(Cuculus sparverioides)寄生,寄生率为1/16(n=16)。发现时白腹短翅鸲巢内有1枚白色的寄生卵和2枚蓝色的寄主卵,且卵已凉,疑为亲鸟弃巢。鹰鹃卵重6.09 g,卵大小20.20 mm×27.73 mm;两枚白腹短翅鸲的卵重分别为2.34 g和2.40 g,大小分别为20.05 mm×14.94 mm和19.95 mm×15.09 mm。鹰鹃的卵重量(6.09 g)和大小(27.73 mm×20.20 mm)均明显大于白腹短翅鸲的卵。卵色光谱测量结果表明,鹰鹃和白腹短翅鸲卵色的反射光谱图差别明显,鹰鹃卵在色度和色调上明显低于白腹短翅鸲,但卵色亮度却明显比白腹短翅鸲卵高,为典型的非模拟寄生卵。     

大杜鹃在白腹短翅鸲巢中寄生繁殖

2009年至2012年期间,在甘肃莲花山自然保护区共发现91个白腹短翅鸲(Hodgsonius phaenicuroides)巢,其中15巢被大杜鹃(Cuculus canorus)寄生,寄生率为16.48%。根据对13枚寄生的大杜鹃卵的观察,其中12枚卵色为浅蓝色,与白腹短翅鸲的深蓝绿色卵差异明显,仅1枚与白腹短翅鸲卵色一致。大杜鹃与白腹短翅鸲的卵重(t =11.208, df=38, P<0.001)和卵短径(t=0.970,df=38, P<0.001)差异极显著。白腹短翅鸲具有识别大杜鹃卵的能力,15巢中只有4巢接受寄生卵并继续孵化,7巢成功识别,剩余4巢无法确定是否识别。白腹短翅鸲为雌鸟单独孵卵,推测识别大杜鹃卵可能只与雌鸟有关。     

小杜鹃对强脚树莺的巢寄生及其卯色模拟

于1999-2009年的鸟类繁殖季(4-8月)对贵州宽阔水自然保护区内的强脚树莺(Cettia fortipes)的繁殖进行监测,并采用光纤光谱仪,通过_芏成分分析、反射光谱、罗宾逊投射等方法对强脚树莺的卵色与小杜鹃(Cuculuspoliocephalus)对其寄生的卵色模拟程度进行分析.研究结果表明,强脚树莺的繁殖成效在不同年份间均尤显著差异,但其巢被捕食率和巢被寄生率都较高,分别为49.26%和9.18%.通过反射光谱分析,表明小杜鹃卵在色调和色度上高度模拟强脚树莺的卵,但其亮度高于宿主卵,而且在人眼无法探测的紫外光部分存在差异.     

中杜鹃捕食比氏鹟莺的卵

许多杜鹃在产下寄生卵之前通常会先叼走或吃掉宿主的1~2枚卵,这说明杜鹃不仅是寄生性繁殖的鸟类,同时可能也是潜在的捕食者。关于杜鹃对其宿主巢捕食的动机,一般认为一是由于杜鹃发现宿主巢时,已不适合寄生,将其捕食或毁坏可迫使宿主重新筑巢,从而杜鹃会获得寄生机会;二则可能由于宿主识别并拒绝了寄生卵,一些杜鹃会通过捕食或破坏宿主的巢,作为对宿主的一种惩罚性报复。2015年6月,在贵州宽阔水自然保护区,通过录像首次记录到中杜鹃(Cuculus saturatus)捕食整巢比氏鹟莺(Seicercus latouchei)卵的行为,表明中杜鹃不仅是许多宿主鸟类的巢寄生者,同时也可能是其巢捕食者。     

骨顶鸡等游禽对不同人为干扰的行为响应

分别于2008年4月至6月和2009年4月至6月,采用目标动物取样法在黑龙江省安邦河湿地和大庆龙凤湿地研究了骨顶鸡等水鸟对人为干扰的行为响应.结果表明:骨顶鸡对行人和机动车辆两种干扰的反应距离类似,但耐受程度有所不同,骨顶鸡对机动车辆干扰的耐受性要好于行人干扰.在以游客等行人干扰为主的安邦河湿地,骨顶鸡以及其他游禽对干扰产生行为反应的比例要高于以机动车辆干扰为主的龙凤湿地,说明相对于行人干扰骨顶鸡对机动车辆更容易耐受;在安邦河湿地,骨顶鸡对划船的反应距离以及反应程度要大于人行走,说明骨顶鸡对于侵入性的干扰更为敏感.此外,对凤头鹛鹏(Podicepscristatus)、黑颈鹏鹧(Podiceps nigricollis)、小鹏鹏(Tachybaptus ruficoUis)、黑水鸡(Gallinula chloropus)、红头潜鸭(Aythya ferina)、赤膀鸭(Anas strepera)、绿头鸭(Anas platyrhynchos)、斑嘴鸭(Anas poecilorhyneha)、绿翅鸭(Arias crecca)、白眉鸭(Anasquerquedula)、赤颈鸭(Ariaspenelope)、琵嘴鸭(Anas clypeata)等游禽对人为干扰的反应距离、耐受距离以及遭受干扰时的反应比例进行了研究,结果显示3种鹛鹧对干扰的耐受距离差异不显著,12种鸭类中红头潜鸭对人为干扰的敏感性要小于其他鸭类,斑嘴鸭和绿头鸭则相对敏感.     

长白山中华秋沙鸭的种内巢寄生

雁形目鸟类的种内巢寄生现象十分普遍,但有关中华秋沙鸭(Mergussquamatus)的种内巢寄生现象未见报道。2019年4和5月,从长白山1个中华秋沙鸭人工巢的视频监控发现,1只雌鸭在亲鸟孵卵时强行进入巢箱趴卧约29 min。其后根据该巢窝卵数的增加、超常窝卵数和窝卵不同步孵化3个指标,确认该巢存在种内巢寄生现象。宿主对进入巢内寄生的个体表现出强烈的攻击行为,但对寄生卵未表现出明显的拒卵行为。由于区域内仍有较多巢箱未被利用,中华秋沙鸭的种内巢寄生行为是否源于对有限巢址资源的竞争,有待进一步研究。     

Fitness costs and benefits of cowbird egg ejection by gray catbirds

Gray catbirds (Dumetella carolinensis) eject over 95% of brown-headedcowbird (Molothrus ater) eggs placed into their nests. Ejectionbehavior could be maintained by selection from either: (1) cowbird parasitism, if the costs of accepting a cowbird egg outweighthe costs of ejecting it, or (2) conspecific parasitism, ifsuch parasitism occurs naturally and results in ejection. Thisstudy tested the above hypotheses by measuring the cost ofacceptance of cowbird parasitism (n= 38 experimentally introducedcowbird chicks) and of cowbird egg ejection (n = 94 experiments),as well as the frequency of natural conspecific parasitismamong 229 catbird nests observed and the frequency of conspecific egg ejection (n = 27 experiments). The conspecific parasitism hypothesis was not supported because catbirds accepted all foreignconspecific eggs placed into their nests, and no natural conspecificbrood parasitism was detected at any nests. The cowbird parasitismhypothesis was strongly supported because the cost of acceptinga cowbird chick (0.79 catbird fledglings) is much greater thanthe cost of ejecting a cowbird egg (0.0022 catbird fledglingsper ejection).     

BEHAVIORAL DEFENSES AGAINST AVIAN BROOD PARASITISM IN SYMPATRIC AND ALLOPATRIC HOST POPULATIONS

The brown-headed cowbird (Molothrus ater) is a widespread, obligate brood parasite of North American passerine birds. In southern Manitoba, where hosts are sympatric with cowbirds, American robins (Turdus migratorius) ejected parasitic eggs from all experimentally parasitized clutches (N = 25) and no eggs were accepted for more than four days. In contrast, robins in northern Manitoba, an area where cowbirds do not breed, accepted parasitic eggs in 33% of nests (N = 18) for at least five days. Acceptance of experimental cowbird eggs by a second host, the yellow warbler (Dendroica petechia), was similar in allopatric (100% of 20 nests) and sympatric (88.6% of 35 nests) populations, but models of a female cowbird elicited greater nest defense by warblers in the area of sympatry. Neither host rejected eggs of conspecifics, thus, rejection of cowbird eggs was not an epiphenomenon of conspecific brood parasitism. These results support the hypothesis that recognition of cowbirds and their eggs evolved as adaptations to counter cowbird parasitism and not some other selection pressure. The expression of anti-parasite defenses by some individuals within allopatric populations further suggests these traits may be controlled genetically but persist in such areas either through the continued introgression of rejecter genes from sympatric populations or because of the low cost of rejection behavior when parasitism is absent or rare.     

The effects of plant density upon pollination success, reproductive effort and fruit parasitism in Cistus ladanifer L. (Cistaceae)

Human activity often causes a decline in the local density of plant populations. Below some critical lower density, populations may suffer a progressive decline in reproductive success because of the difficulties associated with finding suitable mates. Therefore, to conserve endangered plant species it is necessary to understand in greater detail how changes in population density affect different determinants of plant reproductive success. We simultaneously recorded individual plant pollination success, reproductive effort and fruit parasitism in three populations of Cistus ladanifer L. in eastern Portugal. Pollination success declined significantly as distance to the nearest conspecific increased (p<0.001). However, reproductive effort and fruit parasitism showed the opposite pattern (both p<0.001). On average, plants farther than 1 m from their nearest conspecific suffered from three times more fruit parasitism compared to plants closer to a conspecific. Overall, net female reproductive output decreased as nearest neighbor distance rose (p<0.001). Thus, isolated plants were able to compensate only partially for reduced pollination success through increased reproductive effort. We conclude that management plans for plant populations should recognize that reproductive success is the accumulated result of several different processes, which may each respond to plant density in different ways.     

Effects of nest-site characteristics and parental activity on cowbird parasitism and nest predation in Brown-and-yellow Marshbirds

ABSTRACT Nest‐site selection and nest defense are strategies for reducing the costs of brood parasitism and nest predation, two selective forces that can influence avian nesting success and fitness. During 2001–2002, we analyzed the effect of nest‐site characteristics, nesting pattern, and parental activity on nest predation and brood parasitism by cowbirds (Molothrus spp.) in a population of Brown‐and‐yellow Marshbirds (Pseudoleistes virescens) in the Buenos Aires province, Argentina. We examined the possible effects of nest detectability, nest accessibility, and nest defense on rates of parasitism and nest predation. We also compared rates of parasitism and nest predation and nest survival time of marshbird nests during the egg stage (active nests) with those of the same nests artificially baited with passerine eggs after young fledged or nests failed (experimental nests). Most nests (45 of 48, or 94%) found during the building or laying stages were parasitized, and 79% suffered at least one egg‐predation event. Cowbirds were responsible for most egg predation, with 82 of 107 (77%) egg‐predation events corresponding to eggs punctured by cowbirds. Nests built in thistles had higher rates of parasitism and egg predation than nests in other plant, probably because cowbirds were most active in the area where thistles were almost the only available nesting substrate. Parasitism rates also tended to increase as the distance to conspecific nests increased, possibly due to cooperative mobbing and parental defense by marshbirds. The proportion of nests discovered by cowbirds was higher for active (95%) than for experimental (29%) nests, suggesting that cowbirds used host parental activity to locate nests. Despite active nest defense, parental activity did not affect either predation rates or nest‐survival time. Thus, although nest defense by Brown‐and‐yellow Marshbirds appears to be based on cooperative group defense, such behavior did not reduce the impact of brood parasites and predators.     

Aspects of breeding ecology of the eastern olivaceous warbler (Hippolais pallida)

The breeding ecology of eastern olivaceous warblers Hippolais pallida is poorly known. In this study, we provide data on nest site selection and breeding parameters of the species in a population in northwestern Bulgaria, the only one known to be regularly and heavily parasitized by the common cuckoo Cuculus canorus (hereafter cuckoo). Eastern olivaceous warblers only bred within human settlements of the study area, avoiding seemingly suitable habitat outside them. Nests were built in a wide range of plant taxa but ailanthuses Ailanthus altissima and mulberries Morus spp. were most frequently used (21%). After taking into account the availability of vegetation, there was an apparent preference for several plant taxa but not for mulberries. Mean nest height was 1.65 ± 0.98 (0.53–7.60) m, n = 217, and it varied significantly among different types of nesting substrate. Laying date and clutch size of first breeding attempts averaged 10 June ± 0.98 days, n = 101 and 3.9 ± 0.07 (2–5) eggs, n = 72, respectively. Hatching success, fledging success, and breeding success were 42.5, 86.4, and 36.7%, respectively. The main sources of nest mortality were predation and cuckoo parasitism, with no significant difference in the proportion of nests lost to each. Cuckoo parasitism seemed responsible for the relatively low hatching success in this population.     

Factors affecting the breeding success of the south polar skua Catharacta maccormicki at Edmonson Point, Victoria Land, Antarctica

A south polar skua (Catharacta maccormicki) population was studied at Edmonson Point (74°20'S-165°08'E), Victoria Land, Antarctica, in 1998/1999. The local population consisted of 101 pairs, 89 of which were located within a large, loose colony associated with a rookery of about 2,000 pairs of Adélie penguin (Pygoscelis adeliae). Skua nests were clumped around penguin subcolonies. Mean skua Nearest Neighbour Distance (NND) was 21ᆣ m (n=89). NND was positively correlated with the distance from the nearest penguin subcolony. Mean laying date was 24Lj December (n=89). Mean clutch size was 1.9ǂ.2 eggs (n=89). Hatching success was 77% (n=174 eggs laid), and 20.2% of the breeding pairs successfully raised chicks to fledging. Mean number of fledged young was 0.2ǂ.4 per breeding pair (n=89), and 1 per successful pair (n=18). Main causes of breeding failure were intraspecific predation and sibling aggression. Breeding success was negatively related to distance from the nearest penguin nest and to laying date. Because of the extensive and persistent sea-ice cover, penguins represented an important source of food for the skua population.     

Geographic variation in parasitism rates of two sympatric cuckoo hosts in China

Rates of brood parasitism vary extensively among host species and populations of a single host species. In this study, we documented and compared parasitism rates of two sympatric hosts, the Oriental Reed Warbler (Acrocephalus orientalis) and the Reed Parrotbill (Paradoxornis heudei), in three populations in China. We found that the Common Cuckoo (Cuculus canorus) is the only parasite using both the Oriental Reed Warbler and Reed Parrotbill as hosts, with a parasitism rate of 22.4%-34.3% and 0%-4.6%, respectively. The multiple parasitism rates were positively correlated with local parasitism rates across three geographic populations of Oriental Reed Warbler, which implies that higher pressure of parasitism lead to higher multiple parasitism rate. Furthermore, only one phenotype of cuckoo eggs was found in the nests of these two host species. Our results lead to two conclusions: (1) The Oriental Reed Warbler should be considered the major host of Common Cuckoo in our study sites; and (2) obligate parasitism on Oriental Reed Warbler by Common Cuckoo is specialized but flexible to some extent, i.e., using Reed Parrotbill as a secondary host. Further studies focusing on egg recognition and rejection behaviour of these two host species should be conducted to test our predictions.     

Breeding biology of the Red Kite Milvus milvus in Corsica

The breeding biology of the Red Kite Milvus milvus is still little known in the southern part of its range (Mediterranean), despite recent conservation concerns and major declines in most insular populations (Sicily, Sardinia and Balearics). We report here on the breeding biology of the Red Kite in Corsica in 1996–99 and on recent population trends there. In a 42‐km² study area located in the northwest of the island (Balagne region), breeding density was locally high (1.17–1.78 breeding pairs/km²). Breeding dispersion ranged from loosely colonial to dispersed, with average nearest‐neighbour distance of 444 ± 316 m (range 50–2000) (all data as means ± sd). Kites established breeding territories in January–February, and 92.4% of territorial pairs laid a clutch (n = 238). Laying took place between February and May (mean lay date: 27 March ± 16 days, n = 147). Clutch size averaged 2.44 ± 0.71 (1–5 eggs, n = 96), hatching success 66.9% and fledging success 78.6%. Productivity averaged 1.33 ± 0.88 young per breeding attempt (n = 221) and 1.65 ± 0.65 young per successful breeding attempt (n = 173). Overall breeding success was 51.4 ± 38.0% (n = 88). We describe the growth of young (wing, weight, tarsus and bill) and show a marked seasonal decline in clutch size and breeding performance, with pairs laying earlier producing larger clutches and being more successful than later breeding pairs. Unlike most other insular Mediterranean Red Kite populations that have recently declined, the breeding population in the northwest of Corsica, which accounts for c. 25% of the whole island population, increased from 25 to 35 pairs in 1989 to a maximum of 80–90 pairs in 1997. This increase was probably related to the lack of persecution and a local increase in abundance of Rabbits Oryctolagus cuniculus, following their introduction in the late 1970s, which provided an important feeding resource for Kites. Finally, we compare our results with those from other Red Kite populations studied in Europe. We found that there is a latitudinal gradient in laying date and productivity across Western Europe populations, but no evidence of an insular syndrome in the Corsican population.     

Philornis downsi parasitism is the primary cause of nestling mortality in the critically endangered Darwin’s medium tree finch (Camarhynchus pauper)

Darwin’s medium tree finch (Camarhynchus pauper) meets the 2009 International Union for Conservation of Nature Red List criteria for a critically endangered species because it has “a very small range on a single island” and is “declining rapidly owing to the effects of the parasite Philornis downsi”, habitat degradation, and introduced predators. The medium tree finch is only found in patches of remnant highland forest on Floreana Island, where it co-exists with breeding populations of small and large tree finches (C. parvulus and C. psittacula). Here, we examine the intensity of P. downsi in nests of small, medium, and large tree finches on Floreana. We expected that parasite intensity would increase with finch body size, and with greater rainfall, and would also correlate with increased nestling mortality. We found a trend in the expected direction for parasite intensity and rainfall. Combined meta-analytically with data from a previous study, the overall trend for the two studies was significant. We also found a significant linear trend in parasite intensity with finch body size. In addition, the medium tree finch exhibited a somewhat higher parasite intensity than would be expected based on body mass alone. Of 63 active medium tree finch nests, 17 nests had nestlings: all of which were infested with P. downsi. Only 25% of medium tree finch nestlings fledged, 28% were depredated, 41% died due to P. downsi parasitism, and 6% died for other reasons.