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1.
Growth is a fundamental life history trait in all organisms and is closely related to individual fitness. In altricial birds, growth of many traits is restricted to the short period between hatching and fledging and strongly depends on the amount of food that parents deliver and the extent of hatching asynchrony. However, empirical studies of energy allocation to growth of different body size traits as a function of hatching asynchrony are scarce. We studied growth and mortality of Eurasian Hoopoe Upupa epops, a species with a long breeding season and high brood size variance, whose nestlings show pronounced hatching asynchrony, in order to test how hatching asynchrony affects different growth traits in the context of territory quality, season and brood size. The growth of five body traits (body mass, and lengths of tarsus, third primary, bill and longest crest feather) was investigated to understand how it was affected by brood size, hatching date and order, and territory quality. In total, 241 nestlings from 39 nests were measured every 4 days in 2014 in south‐western Switzerland. Brood size, hatching date and hatching order had the strongest influence on growth trajectories, although tarsus growth was only marginally affected by these variables. Nestlings that hatched earlier than their siblings were heavier and had longer third primaries, bills and crest feathers compared with later‐hatched siblings. In territories of high quality, hatching order differences disappeared for body mass growth, but persisted for lengths of third primary, bill and crest feathers. Brood size was inversely associated with third primary, bill and crest feather lengths, but positively associated with body mass. Nestling mortality was higher in later‐hatched nestlings and in broods that were raised in territories of lower quality. Our study shows that in nestlings, energy was allocated differentially between body traits and this allocation interacted with hatching order and territory quality. Rapid mass gain by nestlings was prioritized in order to increase competitive ability. Our results provide support for the brood reduction hypothesis as an explanation of hatching asynchrony in Hoopoes. 相似文献
2.
《Ethology, Ecology and Evolution》2012,24(4):361-374
Intra-brood food distribution in altricial birds can strongly affect nestling competitive hierarchies and subsequent brood reduction. Food allocation patterns result from scramble competitions among the nestlings, various forms of parental favoritism, and/or agonistic interactions among nestlings. Food allocation is related to agonistic interactions among nestlings or to parental favouritism in non-aggressive species. Since white stork chicks are not aggressive and they do not receive direct feeding, parental infanticide has been proposed as an alternative mechanism to control brood reduction. The capacity of white stork parents to control food allocation was examined. We hypothesized that parents favour the senior chick by adjusting prey size to suit its ingestion capacity. We experimentally manipulated (Spain 1996 and Algeria 2004) nestling size by exchanging the senior chick for a larger one. After the exchange parents delivered longer and heavier prey items and they increased the total food amount delivered to the brood, which benefited not only the senior chick but also its smaller nestmate. We also discuss the effect of environmental conditions over brood reduction by comparing chick mortality, intrabrood weight asymmetries and fledging success in years with above (2003 and 2004) and below (2002) average rainfall in the area. We conclude that parents may control intra-brood food distribution which enables them to invest more in larger sibs but not (under favourable conditions) at the expense of junior chicks. 相似文献
3.
4.
We describe the main results of a monitoring study at Lake Myvatn, northern Iceland, begun in 1975. The aims were to find factors that limit production of young and cause changes in density of breeding ducks of several species. We estimated numbers of ducks in spring, before nesting, numbers of ducklings produced, and numbers moulting. Chironomid and simuliid dipterans were monitored with window traps. In all duck species studied, production of young was correlated with food abundance. Reproductive performance determined subsequent changes in spring population density of Eurasian Wigeon, Tufted Duck, Greater Scaup, Common Scoter and Harlequin Duck. The spring population of Barrow's Goldeneye apparently did not respond to variation in reproductive success. Moulting numbers of male Tufted Duck were related to chironomid abundance, but not those of Scaup and Barrow's Goldeneye. Moulting numbers were not associated with previous reproductive output. 相似文献
5.
John L. Wray 《Physiologia plantarum》1993,89(3):607-612
Nitrite reductase (ferredoxin:nitrite oxidoreductase, EC 1.6.6.1) carries out the six-electron reduction of nitrite to ammonium ions in the chloroplasts/plastids of higher plants. The complete or partial nucleotide sequences of a number of nitrite reductase apoprotein genes or cDNAs have been determined. Deduced amino acid sequence comparisons have identified conserved regions, one of which probably is involved in binding the sirohaem/4Fe4S centre and another in binding the electron donor, reduced ferredoxin. The nitrite reductase apoprotein is encoded by the nuclear DNA and is synthesised as a precursor carrying an N-terminal extension, the transit peptide, which acts to target the protein to, and within, the chloroplast/plastid. In those plants examined the number of nitrite reductase apoprotein genes per haploid genome ranges from one (barley, spinach) to four ( Nicotiana tabacum ). Mutants defective in the nitrite reductase apoprotein gene have been isolated in barley. During plastidogenesis in etiolated plants, synthesis of nitrite reductase is regulated by nitrate, light (phytochrome), and an uncharacterised 'plastidic factor' produced by functional chloroplasts. In leaves of green, white-light-grown plants up-regulation of nitrite reductase synthesis is achieved via nitrate and light and down-regulation by a nitrogenous end-product of nitrate assimilation, perhaps glutamine. A role for phytochrome has not been demonstrated in green, light-grown plants. Light regulation of nitrite reductase genes is related more closely to that of photosynthetic genes than to the nitrate reductase gene. In roots of green, white-light-grown plants nitrate alone is able to bring about synthesis of nitrite reductase, suggesting that the root may possess a mechanism that compensates for the light requirement seen in the leaf. 相似文献
6.
DN Reznick RD Bassar J Travis F Helen Rodd 《Evolution; international journal of organic evolution》2012,66(9):2903-2915
In prior research, we found the way guppy life histories evolve in response to living in environments with a high or low risk of predation is consistent with life-history theory that assumes no density dependence. We later found that guppies from high-predation environments experience higher mortality rates than those from low-predation environments, but the increased risk was evenly distributed across all age/size classes. Life-history theory that assumes density-independent population growth predicts that life histories will not evolve under such circumstances, yet we have shown with field introduction experiments that they do evolve. However, theory that incorporates density regulation predicts this pattern of mortality can result in the patterns of life-history evolution we had observed. Here we report on density manipulation experiments performed in populations of guppies from low-predation environments to ask whether natural populations normally experience density regulation and, if so, to characterize the short-term demographic changes that underlie density regulation. Our experiments reveal that these populations are density regulated. Decreased density resulted in higher juvenile growth, decreased juvenile mortality rates, and increased reproductive investment by adult females. Increased density causes reduced offspring size, decreased fat storage by adult females, and increased adult mortality. 相似文献
7.
杂色山雀的繁殖生态 总被引:1,自引:0,他引:1
2004—2006年3—7月在辽宁省白石砬子国家级自然保护区对杂色山雀的繁殖生态进行了观察研究。结果表明:该鸟繁殖期为3—7月,筑巢地除了树洞之外,还见在墙缝、石缝、金腰燕旧巢及电柱孔洞中筑巢,筑巢主要由雌鸟完成,雄鸟从旁协助;产卵期为5~8d,日产1枚,窝卵数为(6.92±0.92)枚(n=13);产满窝卵数后即开始孵化;孵化由雌鸟单独完成,孵化期(14.00±0.00)d(n=10),坐巢时间(570.00±11.02)min.d-1(n=9)(不含夜间),平均坐巢时间(57.00±6.75)min.次-1(n=9),雄鸟担任警卫任务,孵化期较为敏感,受到干扰易弃巢;育雏期(17.50±0.58)d(n=4),由雌雄鸟共同喂雏,雏鸟出飞后先是在亲鸟的带领下在巢周活动,之后活动范围逐渐扩展,2~3d后基本离开巢区。 相似文献
8.
红头长尾山雀繁殖生态的研究 总被引:8,自引:2,他引:8
在安徽合肥紫蓬山区,对红头长尾山雀的繁殖生态进行了系统的观察,并研究了雏鸟的生长特征。研究表明,红头长尾山雀自3月中旬以后开始发情,3月下旬开始营巢,巢位于杉树枝下,球形侧开口或侧顶开口。4月初产卵,每窝平均产6.25枚卵,孵化期为15—16d,孵化率为88%。育维期15—16d,22维全部成活到离巢,雏成活率达100%。体重、翅、嘴峰、跗跖、第5枚初级飞羽和尾羽等形态学参数适合用Logistic曲线方程拟合,拟合参数中,嘴峰的拐点最小,飞羽、翅和尾羽的增长率较高,表明与取食有关的形态优先发育,与飞行有关的形态则在后期发育较快。 相似文献
9.
乌鸫繁殖生态的研究 总被引:9,自引:0,他引:9
乌鸫 (Turdusmerulamandarinus)是紫蓬山区常见的留鸟[1,3 ] 。吴至康等[2 ] 报道其在贵州的繁殖习性。有关巢空间资源利用特点、护雏行为、雏鸟生长模式的研究未见报道。本文是 1996年 3月份在安徽省肥西县的几个居民点对其繁殖初期活动进行了初步观察 ,4~7月又在紫蓬山区国家级森林公园的圆通山林区对其繁殖生态进行了系统研究的结果。现报道如下。1 工作方法根据样地鸟巢统计繁殖鸟类的数量 ,记录巢位特征以及巢和卵的参数 ,观察繁殖行为 ,记录雏鸟的生长情况。拟合雏鸟的生长曲线方程[9] 。2 结 果2 1 繁殖… 相似文献
10.
Kevin B. Potts Colin A. Chapman Jeremiah S. Lwanga 《The Journal of animal ecology》2009,78(6):1269-1277
1. Despite a long history of research on the influence of fruit availability on the population density of large-bodied vertebrate frugivores, operational understanding of the factors regulating density in these taxa remains elusive. We propose that fruit resources can be distinguished from one another on the basis of their functional role for the animals in question, and that such a classification system can aid in identifying the most influential determinants of frugivore density.
2. We compared the availability of several resource classes between two sites in Kibale National Park, Uganda separated by only 12 km yet differing threefold in density of chimpanzees ( Pan troglodytes ).
3. We categorized plant species used for fruit by chimpanzees according to their availability relative to habitat-wide fruit productivity, and by their tendency towards inter-individual fruiting synchrony. We predicted that the site of high chimpanzee density would support a higher density of food plant species tending to produce crops during periods of high habitat-wide productivity [high fruit abundance (HFA foods)] and of those tending to fruit synchronously among individuals during times of low habitat-wide availability (sLFA foods). The first food class should provide chimpanzees with a high nutrient density (and thus promote population growth), whereas the second should provide stable subsistence during lean periods and thus a temporally consistent resource base.
4. Counter to our prediction, only sLFA resources were more abundant at the site of high chimpanzee density than at the site of low density. We suggest that sLFA resources are most important in influencing density of large-bodied frugivores. 相似文献
2. We compared the availability of several resource classes between two sites in Kibale National Park, Uganda separated by only 12 km yet differing threefold in density of chimpanzees ( Pan troglodytes ).
3. We categorized plant species used for fruit by chimpanzees according to their availability relative to habitat-wide fruit productivity, and by their tendency towards inter-individual fruiting synchrony. We predicted that the site of high chimpanzee density would support a higher density of food plant species tending to produce crops during periods of high habitat-wide productivity [high fruit abundance (HFA foods)] and of those tending to fruit synchronously among individuals during times of low habitat-wide availability (sLFA foods). The first food class should provide chimpanzees with a high nutrient density (and thus promote population growth), whereas the second should provide stable subsistence during lean periods and thus a temporally consistent resource base.
4. Counter to our prediction, only sLFA resources were more abundant at the site of high chimpanzee density than at the site of low density. We suggest that sLFA resources are most important in influencing density of large-bodied frugivores. 相似文献
11.
Troy I. Wellicome L. Danielle Todd Ray G. Poulin Geoffrey L. Holroyd Ryan J. Fisher 《Ecology and evolution》2013,3(8):2684-2695
Food availability is an important limiting factor for avian reproduction. In altricial birds, food limitation is assumed to be more severe during the nestling stage than during laying or incubation, but this has yet to be adequately tested. Using food‐supplementation experiments over a 5‐year period, we determined the degree and timing of food limitation for burrowing owls (Athene cunicularia) breeding in Canada. Burrowing owls are an endangered species and food limitation during the nestling stage could influence reproductive performance of this species at the northern extent of their range. Supplemented pairs fledged on average 47% more owlets than unfed pairs, except during a year when natural food was not limiting (i.e., a prey irruption year). The difference in fledgling production resulted from high nestling mortality in unfed broods, with 96% of all nestling deaths being attributed to food shortage. Supplemental feeding during the nestling period also increased fledgling structural size. Pairs fed from the start of laying produced the same number of hatchlings as pairs that received no supplemental food before hatch. Furthermore, pairs supplemented from egg laying to fledging and pairs supplemented during the nestling period alone had the same patterns of nestling survival, equal numbers of fledglings, and similar fledgling mass and structural size. Our results provide empirical support for the hypothesis that the nestling period is the most food‐limited phase of the breeding cycle. The experimental design we introduce here could be used with other altricial species to examine how the timing of food limitation differs among birds with a variety of life‐history strategies. For burrowing owls, and other species with similar life histories, long‐term, large‐scale, and appropriately timed habitat management increasing prey abundance or availability is critical for conservation. 相似文献
12.
Fisher's theory predicts equal sex ratios at the end of parentalcare if the costs and benefits associated with raising eachsex of offspring are equal. In raptors, which display variousdegrees of reversed sexual size dimorphism (RSD; females thelarger sex), sex ratios biased in favor of smaller males areonly infrequently reported. This suggests that offspring ofeach sex may confer different fitness advantages to parents.We examined the relative returns associated with raising eachsex of offspring of the brown falcon Falco berigora, a medium-sizedfalcon exhibiting RSD (males approximately 75% of female bodymass) and subsequent sex ratios. Female nestlings hatched eitherfirst or second did not receive more food nor did they hatchfrom larger eggs or remain dependent on parents for longer periodsthan male offspring from these hatch orders. Together with previousstudies this result indicates that even in markedly dimorphicspecies, the required investment to raise the larger sex islikely to be less than that predicted by body size differencesalone. Moreover, among last-hatched nestlings, both sexes faceda reduced food allocation and suffered a slower growth rateand thus final body size, with a concurrent increased probabilityof mortality. For last-hatched females the reduction in foodallocation was more marked, with complete mortality of all last-hatchedfemale nestlings monitored in this study. Once independent,males of any size but only larger females are likely to be recruitedinto the breeding population. The sex-biased food allocationamong last-hatched offspring favoring males thus reflects therelative returns to parents in raising a small member of eachsex. 相似文献
13.
内蒙古达赉湖国家级自然保护区短趾百灵繁殖生态学初报 总被引:1,自引:0,他引:1
本文对内蒙古达赉湖国家级自然保护区短趾百灵繁殖生态进行了初步研究,共记录到短趾百灵繁殖巢37个.筑巢期7~10 d.巢外径91.95 mm±3.85 mm(n=37),巢内径53.89 mm±3.29 mm(n=37),巢深43.62 mm±5.36 mm(n=37).平均窝卵数3.05枚±0.51枚.孵卵期10~12 d.孵化率、离巢率和繁殖成功率分别为83.3%、94.1%和54.1%.雏鸟食性以直翅目昆虫幼虫为主. 相似文献
14.
Roswitha Junker-Bornholdt Michael Wagner Matthias Zimmermann Stefan Simonis Karl-Heinz Schmidt und Wolfgang Wiltschko 《Journal of Ornithology》1998,139(2):131-139
Zusammenfassung Im Februar 1992 wurde an der in Bau befindlichen Autobahn BAB 66 zwischen Steinau und Schlüchtern (5021'N, 0931'E) ein Nistkastenkontrollgebiet mit 310 Nistkästen eingerichtet, um die Auswirkungen der Autobahn vor und nach Inbetriebnahme auf die Brutbiologie von Meisen zu untersuchen. Als Vergleichsgebiete dienen ein direkt benachbartes sowie ein ca. 5 km entferntes Untersuchungsgebiet. Zum Vergleich der Gewichtsentwicklung der Nestlinge wurde ein drittes autobahnfernes Gebiet herangezogen.In einzelnen Jahren finden sich zwischen den Gebieten Unterschiede in der Zusammensetzung der Brutpopulation, der Besetzungsrate der Nistkästen, dem Legebeginn, der Gelegegröße, der Schlüpfrate oder im Bruterfolg. Diese Unterschiede treten in verschiedenen Jahren und in unterschiedlichen Gebieten auf, so daß sich keine generelle Abweichung des Gebietes an der Autobahn von den straßenfernen Gebieten feststellen läßt. Die Eröffnung der Autobahn hatte keinen Effekt auf die untersuchten Parameter.Die Gewichte der Nestlinge im Gebiet an der Autobahn waren im Jahr 1996 nur am 12. und 13. Nestlingstag signifikant geringer als die Gewichte der Nestlinge in einem autobahnfernen gleichartig strukturierten Biotop. Die Ausflugsgewichte der Jungvögel an der A66 liegen jedoch ca. 2 g höher als in städtischen Biotopen.Störungen durch den Straßenverkehr, wie sie von anderen Autoren berichtet werden, ließen sich in unserem Untersuchungsgebiet nicht feststellen. In diesem Zusammenhang werden die geringe Störungsempfindlichkeit der Kohl- und Blaumeisen sowie der bisher geringe Verkehr auf der Autobahn diskutiert.
The impact of a motorway in construction and after opening to traffic on the breeding biology of Great Tit (Parus major) and Blue Tit (P. caeruleus)
Summary In February 1992, a study area (A 66) with 310 nestboxes was installed along the construction line of a four laned motorway between Steinau and Schlüchtern (5021'N, 0931'E). One area in the immediate neighbourhood (VG1) and one 5 km distant (VG2) from the study area at the motorway (see Fig. 1) served as controls for comparison. In all three areas, the nestboxes were checked weekly during the breeding season from the beginning of May until July. Species composition of the birds using nestboxes, rate of occupation of nestboxes, and, for Great Tits (Parus major) and Blue Tits (P. caeruleus), date of the first egg, clutch size, hatching rate and number of birds fledged were recorded. The study included 5 breeding seasons from 1992 to 1996, 3 years during the period of construction and 2 years after the opening of the motorway to traffic in December 1994. In 1996, the nestling weight of 20 broods of Great Tits at the A66 was recorded daily and compared with that of all nestlings in another study area (VG3, see Fig. 1).The data were analyzed separately for each year. Distributions of frequencies were analyzed with the x2 test, the other data with the Kruskal-Wallis-Test (H-Test). In case of significant differences between the study areas, the Mann Whitney U-test was used to determine which study area differed from the others. Nestlings bodymass was compared using the t-test.The species composition was similar in all three areas (Fig. 2), and it did not change after the opening of the motorway to traffic. The rate of occupation of the nestboxes, dates of laying of the first egg, clutch size, hatching rate and breeding success vary between years and between study areas (Table 1 to 5); data that differ significantly from those of two other areas are indicated by bold print. Such differences were observed in various years and involved all three areas. In study area A66, clutch size of Great Tits was higher in 1993; hatching success of Great Tits was lower in 1994 and that of Blue Tits was lower in 1993. However, there was no general trend that area A66 at the motorway was different from the other areas, either before or after being opened to the traffic. The weight of nestlings in study area A66 at the motorway was similar to that in comparable area nearby; only on day 12 and 13 after hatching was it slightly lower (Tab. 6). The last measurement on day 15 indicates a nestling weight of 16.2 g for the area at the motorway, which is in normal for deciduous forest habitats and approximately 2 g higher than that recorded in urban habitats.In brief, the motorway did not affect the species composition, rate of occupied nestboxes or the various breeding parameters; in particular, the moving traffic after opening did not seem to have any effect. The breeding parameters from the study area at the motorway were typical for the Schlüchtern region. Density reductions in breeding populations, as discussed by several authors, or disturbances caused by moving traffic, as previously reported, were not observed in our study. However, our key species, Great Tits and Blue Tits, are not generally very sensitive to interferences. Also, the level of traffic on the motorway was still rather low. This must be considered when our findings are generalized.相似文献
15.
Takashi Saitoh 《Population Ecology》1991,33(2):367-386
The effects of breeding territoriality on the stability of grey red-backed vole (Clethrionomys rufocanus bedfordiae) populations were investigated on a control grid and a grid on which the voles were fed, in an outdoor enclosure in Hokkaido, Japan. Vole populations were monitored by live trapping from 1984 to 1986: (1) Population density was 2–7 times greater on the experimental grid to which food was added than on the control grid. Reproductive output was more closely associated with the difference in density between grids than survival or dispersal (immigration and emigration) rates. (2) The number of adult females and pregnancy rate of the experimental population were significantly greater than those of the control one. The difference in the number of adult females between the populations was greater than that in pregnancy rate. (3) The proportion of successful litters and the number of weanlings per litter were not significantly different between the control and experimental population. (4) Adult females held territories on both the control and experimental grid; they were spaced out more than would be expected from random occupation. The territories overlapped more on the experimental grid than on the control grid. (5) Mean territory size of adult females on the experimental grid was about half of that on the control grid. The territory size was correlated negatively with population density. (6) The proportion of trap sites that were used by adult females was significantly greater on the experimental grid than on the control grid. This suggests that adult females on the experimental grid used the area more extensively. This factor, in association with territory size and overlapping of territory, was also important in causing the difference in the number of adult females between the grids. (7) These results call into question the hypothesis that territoriality stabilizes the density in populations of Clethrionomys. 相似文献
16.
鹟莺属(Seicercus)鸟类的繁殖资料十分缺乏。2015年4~8月,采用录像全程监控的方法,在贵州宽阔水国家级自然保护区,对4巢栗头鹟莺(S.castaniceps)的繁殖过程进行了完整观察。栗头鹟莺的繁殖期主要集中在5~7月,巢址选择专一性较强,均筑巢于公路边的土坎内壁,距路(1.3±1.2)m,巢为球状侧开口,巢材主要为新鲜苔藓及细草根,巢高(2.2±0.6)m,巢宽(10.9±1.5)cm,杯宽(3.3±0.5)cm,巢深(9.5±1.9)cm,杯深(5.5±1.0)cm。窝卵数(4.5±0.6)枚(4~5枚),卵重(0.92±0.04)g,卵长(14.30±0.30)mm,卵宽(11.22±0.23)mm,卵体积(0.92±0.05)mm3(n=18)。亲鸟在产满窝卵后开始孵卵,孵卵期12~13 d,在孵卵中期(第5~9天)亲鸟的孵卵时间开始增加,翻卵次数增多,在孵卵后期(第10~13天)亲鸟的孵卵时间和翻卵次数基本保持不变。育雏期13~14 d。雌、雄共同育雏,雏鸟在3日龄时,体重和跗跖开始显著增长,在7日龄时,增长速度变缓。孵化率为88.9%(16/18),营巢成效为100%,出飞成效为3.3只/巢。 相似文献
17.
Gregorio Moreno‐Rueda Francisco Campos Francisco Gutiérrez‐Corchero María Ángeles Hernández 《Ibis》2017,159(1):230-234
Despite major advances in sex ratio theory, how offspring sex should vary with hatching order remains unclear. We examine nestling sex ratio in the Southern Grey Shrike Lanius meridionalis according to hatching order and clutch size. Southern Grey Shrike nestlings present a different sex ratio with body‐mass rank order depending on clutch size. When the clutch size was five eggs (with a very low risk of brood reduction; 13%) the less costly sex (male) was found at the end of the body mass hierarchy. However, when clutch size was six eggs (with a high risk of brood reduction; 42%) the larger sex (female) was found at intermediate positions in the hatching order, possibly to decrease competitive asymmetries. 相似文献
18.
The onset of incubation before the end of laying imposes asynchrony at hatching and, therefore, a size hierarchy in the brood. It has been argued that hatching asynchrony might be a strategy to improve reproductive output in terms of quality or quantity of offspring. However, little is known about the mediating effect of hatching asynchrony on offspring quality when brood reduction occurs. Here, we investigate the relationship between phenotypic quality and hatching asynchrony in Common Kestrel Falco tinnunculus nestlings in Spain. Hatching asynchrony did not increase breeding success or nestling quality. Furthermore, hatching asynchrony and brood reduction had different effects on nestlings’ phytohaematogglutinin (PHA)‐mediated immune response and nestling growth. In asynchronous and reduced broods (in which at least one nestling died), nestlings showed a stronger PHA‐mediated immune response and tended to have a smaller body size compared with nestlings raised in synchronous and reduced broods. When brood reduction occurred in broods hatched synchronously, there was no effect on nestling size, but nestlings had a relatively poor PHA‐mediated immune response compared with nestlings raised in asynchronous and reduced broods. We suggest that resources for growth can be directed to immune function only in asynchronously hatched broods, resulting in improved nestling quality, as suggested by their immune response. We also found that males produced a greater PHA‐mediated immune response than females only in brood‐reduced nests without any effect on nestling size or condition, suggesting that females may trade off immune activities and body condition, size or weight. Overall, our results suggest that hatching pattern and brood reduction may mediate resource allocation to different fitness traits. They also highlight that the resolution of immune‐related trade‐offs when brood reduction occurs may differ between male and female nestlings. 相似文献
19.
Arnthor Gardarsson 《Hydrobiologia》2006,567(1):89-100
Studies of temporal processes at Lake Mývatn, Iceland, on three scales, millennial, centennial and decadal, are reviewed and a summary is presented of the main results of waterfowl population monitoring studies conducted during the past three decades. The characteristics of shallow, subarctic Lake Mývatn and its volcanic environment, are outlined, as well as recent conflicts between development and conservation. Mining of the bottom sediment of Lake Mývatn has been a major agent causing habitat destruction and damage to the food web. Population limitation of waterbirds at Mývatn is discussed, as three research questions and emerging answers: (1) How is reproductive output determined? All species studied showed positive correlations of production of young with levels of aquatic insects, catastrophic weather was rarely important; (2) How is the dispersion of breeding ducks determined? Densities of migratory species are determined mainly by resource levels on the breeding ground in the year before they return to the breeding area; a year-round resident species, Bucephala islandica, adjusts its density to the current availability of insect food in each of two main habitats used; (3) How are flyway populations of ducks determined? For most species, there is not enough information on total numbers and the state of the habitat on a flyway scale. In B. islandica, there are indications that the total population is limited by resources in winter. The Mývatn study area is dominated by a single, shallow and eutrophic lake and for many waterbird species the area seems to form a single functional unit. This leads to significant correlations when comparing demography with environmental conditions, such as food resources. 相似文献
20.
C. H. Siven 《International Journal of Anthropology》1991,6(2):97-109
A statistical method (based on the maximum likelihood principle) for estimating mortalities of skeletal populations is presented.
The method can be applied both when osteological age groups are not overlapping as well as when they are. The results are
presented as point estimates and as confidence intervals around these. The method is applied to two series from the Middle
Ages: Westerhus and Helgeandsholmen. 相似文献