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1.
Effects of begging on growth rates of nestling chicks   总被引:8,自引:3,他引:5  
We investigated whether an increase in begging levels delaysgrowth of chicks. In experiment 1, we hand-reared nine pairsof ring dove squabs, divided into a control and a begging group.All squabs received similar amounts of food, but those in thebegging group had to beg for a prolonged period in order tobe fed, while squabs in the control group received food withoutbegging. Squabs stopped responding to the treatment after 10days and, at that time, there was no effect of induced beggingon their body mass. In experiment 2, we hand-reared 27 pairsof magpie chicks for 3 days. The design of experiment 2 wassimilar to that of experiment 1. Daily food intake and beggingaffected growth rates. On average, chicks in the begging groupgrew 0.8 g/day less than control chicks, which represents adecrease of 8.15% in growth rate. Because growth is usuallypositively associated with expected fitness, this demonstratesthat begging is a costly behavior, an assumption routinelymade in models of begging behavior.  相似文献
2.
Nest size has been suggested to be a sexually selected traitindicating parental ability of both males and females. To testwhether a female's reproductive decisions (e.g., clutch sizeand starting incubation) change in relation to experimentalmanipulation of nest size, as would be predicted if nest sizeis a sexually selected signal reflecting the male's parental quality, we manipulated nest size in a population of monogamousmagpies before laying by adding or removing about 20 cm oflarge sticks in the roof of magpie nests. On the one hand,we found that clutch size of reduced nests was smaller thanthat of control or enlarged nests. Moreover, clutch size was significantly related to nest size after manipulation, whichindicates that females adjust clutch size to the final sizeof the nest, nest size thereby being a good candidate for asexually selected trait. On the other hand, number of eggshatched during the first day is hypothesized to be related to the expected available resources during nestling growth, andsubsequent nestlings hatched are likely to die due to broodreduction if resources are not sufficient to raise well-developednestlings. Nest size is hypothesized to inform females abouta male's willingness to invest in reproduction, and we foundthat in broods of experimentally reduced nests, females startedto incubate earlier in the laying sequence than they did inbroods of control or enlarged nests. Moreover, in experimentallyreduced nests, fewer nestlings hatched during the first day,and the difference in body mass between the first and the fourthnestling hatched increased. This result is in accordance withthe hypothesis that the female's decision of when to start incubationin the laying sequence is mediated by nest size, a sexuallyselected trait signaling parental quality. We discuss alternativeexplanations for the results such as the possibility that nestsof different treatments may differ in their thermoregulationproperties or in their protection against predators.  相似文献
3.
四川省喜鹊地理分布的变迁   总被引:4,自引:2,他引:2  
喜鹊(Pica pica)曾是四川各地最常见的鸟类,但20世纪后期喜鹊却在四川的农耕区和城镇消失了,并持续至今。根据对1995年7月~2002年4月在四川各地搜集的野外数据分析,结合文献资料,说明喜鹊种群数量在四川于20世纪50年代后期已呈下降趋势,70年代开始出现局部消失现象,80年代是其局部灭绝的高峰期,并且消失现象从盆地扩展到周边山地和川西高原山地。进入90年代在四川已形成盆地罕见区,盆周山地、川西南山地局部分布区、川西高原广布区的分布格局。分析讨论了引起其地理分布变迁的原因,认为这是大量砍伐林木、滥用农药、人为毁巢和猎杀所造成的,而滥用剧毒农药、鼠药的影响最大。  相似文献
4.
A long-term study of the interactions between a brood parasite, the great spotted cuckoo Clamator glandarius, and its primary host the magpie Pica pica, demonstrated local changes in the distribution of both magpies and cuckoos and a rapid increase of rejection of both mimetic and non-mimetic model eggs by the host. In rich areas, magpies improved three of their defensive mechanisms: nest density and breeding synchrony increased dramatically and rejection rate of cuckoo eggs increased more slowly. A stepwise multiple regression analysis showed that parasitism rate decreased as host density increased and cuckoo density decreased. A logistic regression analysis indicated that the probability of changes in magpie nest density in the study plots was significantly affected by the density of magpie nests during the previous year (positively) and the rejection rate of mimetic model eggs (negatively). These results are consistent with a hypothesis (the intermittent arms race hypothesis) of spatially structured cyclic changes in parasitism. During periods of parasitism, host defences continuously improve, and as a consequence, the fitness gains for parasites decrease. When host defences against parasites reach a high level, dispersing parasites have a selective advantage if they are able to emigrate to areas of low resistance. Once parasites have left an area hosts will lose their defensive adaptations due to their cost in the absence of parasitism. The scene is then set for re-colonization by great spotted cuckoos. Received: 7 May 1998 / Accepted: 24 August 1998  相似文献
5.
Passerine hosts of parasitic cuckoos usually vary in their abilityto discriminate and reject cuckoo eggs. Costs of discriminationand rejection errors have been invoked to explain the maintenanceof this within-population variability. Recently, enforcementof acceptance by parasites has been identified as a rejectioncost in the magpie (Pica pica) and its brood parasite, the greatspotted cuckoo (Clamator glandarius). Previous experimentalwork has shown that rejecter magpies suffer from increased nestpredation by the great spotted cuckoo. Cuckoo predatory behavioris supposed to confer a selective advantage to the parasitebecause magpies experiencing a reproductive failure may providea second opportunity for the cuckoo to parasitize a replacementclutch. This hypothesis implicitly assumes that magpies modulatetheir propensity to reject parasite eggs as a function of previousexperience. We tested this hypothesis in a magpie populationbreeding in study plots varying in parasitism rate. Magpie pairs thatwere experimentally parasitized and had their nests depredated,after their rejection behavior had been assessed, changed theirbehavior from rejection to acceptance. The change in host behaviorwas prominent in study plots with high levels of parasitism,but not in plots with rare or no cuckoo parasitism. We discussthree possible explanations for these differences, concludingthat in study plots with a high density of cuckoos, the probability fora rejecter magpie nest of being revisited and depredated bya cuckoo is high, particularly for replacement clutches, and,therefore, the cost for magpies of rejecting a cuckoo egg ina replacement clutch is increased. Moreover, in areas with highlevels of host defense (low parasitism rate), the probabilityof parasitism and predation of rejecter-magpie nests by thecuckoo is reduced in both first and replacement clutches. Therefore,rejecter magpies in such areas should not change their rejectionbehavior in replacement clutches.  相似文献
6.
Brood parasites dramatically reduce the reproductive successof their hosts, which therefore have developed defenses againstbrood parasites. The first line of defense is protecting thenest against adult parasites. When the parasite has successfullyparasitized a host nest, some hosts are able to recognize andreject the eggs of the brood parasite, which constitutes the secondline of defense. Both defense tactics are costly and would be counteractedby brood parasites. While a failure in nest defense implies successfulparasitism and therefore great reduction of reproductive successof hosts, a host that recognizes parasitic eggs has the opportunityto reduce the effect of parasitism by removing the parasiticegg. We hypothesized that, when nest defense is counteractedby the brood parasite, hosts that recognize cuckoo eggs shoulddefend their nests at a lower level than nonrecognizers becausethe former also recognize adult cuckoos. Magpie (Pica pica) hoststhat rejected model eggs of the brood parasitic great spottedcuckoo (Clamator glandarius) showed lower levels of nest defensewhen exposed to a great spotted cuckoo than when exposed toa nest predator (a carrion crow Corvus corone). Moreover, magpiesrejecting cuckoo eggs showed lower levels of nest defense againstgreat spotted cuckoos than nonrecognizer magpies, whereas differencesin levels of defense disappeared when exposed to a carrion crow.These results suggest that hosts specialize in antiparasitedefense and that different kinds of defense are antagonistically expressed.We suggest that nest-defense mechanisms are ancestral, whereasegg recognition and rejection is a subsequent stage in the coevolutionaryprocess. However, host recognition ability will not be expressedwhen brood parasites break this second line of defense.  相似文献
7.
北京高校喜鹊巢址选择的主要生态因素   总被引:2,自引:0,他引:2  
陈侠斌  何静  张薇 《四川动物》2006,25(4):855-857,861
根据从2003~2005年每年一次关于北京近20所高校校园喜鹊(Pica pica sericea)巢址的分布情况的调查,对影响高校校园喜鹊巢址选择的因素进行了分析,结果表明营巢树因素(营巢树的高度、胸径、巢位高度、巢上方的植被盖度)和环境因素(嘈杂度和食物的丰富程度)都会影响喜鹊对巢址的选择。研究结果对如何进行校园绿地的规划以及鸟类保护具有一定的指导作用。  相似文献
8.
Adult great spotted cuckoos Clamator glandarius damage the eggsof their magpie Pica pica host without removing them from thenest or eating them but by producing the death of the embryo.Observations as well as experiments were used to test severalpredictions of two different possibilities: great spotted cuckooegg-damaging behavior is a parasitic tactic resulting froma direct selection process (the adaptation hypothesis), oregg damage is caused by thick-shelled cuckoo eggs which evolvedto avoid breakage during rapid laying (the nonadaptation hypothesis).Previously, we provided experimental evidence that egg damageincreased the breeding success of cuckoos when they laid lateduring the laying sequence of the magpie. However, when theylaid early, egg-damaging behavior did not increase cuckoo breedingsuccess, contrary to the adaptation hypothesis. In an experimental study, when we simulated laying behavior by the great spottedcuckoo, we found that (1) the number of damaged magpie eggswas significantly lower than in natural parasitism, and (2)whereas in the experimental manipulations the number of damagedeggs did not depend on the number of magpie eggs, in natural parasitism, the number of damaged eggs increased with clutchsize of the magpie. These results support the predictions ofthe adaptation hypothesis, implying that egg damage is notan incidental consequence of rapid egg laying, but an adaptation.  相似文献
9.
Interactions between parasitic cuckoos and their hosts represent a classic example of coevolution, where adaptations in the parasite to exploit the host select for defences, which in turn select for new parasite adaptations. Current interactions between the two parties may be at an evolutionary equilibrium or, alternatively, a coevolutionary arms race may be taking place. By taking into account the effect of gene flow in 15 European magpie ( Pica pica ) populations, we studied the coevolutionary interactions with its brood parasite, the great spotted cuckoo ( Clamator glandarius ). Our results suggest that, in Europe, magpies and cuckoos are engaged in an ongoing coevolutionary process because, despite controlling for the large amounts of gene flow among different magpie populations, we still found a positive relationship between host defence (i.e. foreign egg recognition and rejection) and parasite selection pressure.  相似文献
10.
Summary In experimental studies of avian hatching paterns offspring sex has been neglected. This may be a problem if nestling growth and mortality is sex biased, and if this bias is influenced by hatching spread. In a field study of two crow species, the magpie Pica pica and the hooded crow Corvus corone cornix, we manipulated hatching spread. Both species have asynchronous hatching, and adult males are larger than females by 12–14%. The sex ratios obtained from the different experimental groups on day 24 post-hatch (total sample n = 403) did not deviate significantly from unity, nor did the sex ratios obtained among young newly hatched in an incubator (total sample n = 305). Male and female offspring were of similar size at hatching but males were larger on day 24 post-hatch. Males seemed to be more costly to rear than females, judging by the 20% difference in the mean amounts of food found in the gizzards of the young on day 24 post-hatch. Dimorphism in body size did not seem to be influenced by degree of hatching spread. Asynchronous hatching did not seem to be needed to produce high quality offspring of the larger sex (i.e. males), nor did asynchronous hatching help to ensure equal parental investment in male and female progeny. One reason for the latter negative results may be that the size dimorphism of the two crow species studied were relatively small.  相似文献
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