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1.
    
An influential period in avian life‐cycles is the annual breeding season, when competition over suitable nesting sites and territories is a key factor that can determine fitness and distribution, especially for species that are highly selective in their nesting habitats. We analysed nest‐site characteristics, breeding success and competitive interactions between two apex predator populations. Whereas the Short‐toed Eagle Circaetus gallicus has nested in the Judean Foothills (Israel) for a long time, the Long‐legged Buzzard Buteo rufinus has only invaded the nesting habitat of the Short‐toed Eagle during their breeding season in the last two decades. These two recently sympatric species have similar nesting ecology and frequently use the same nests. They are therefore expected to compete over nesting sites and territories. We analysed interspecific interactions between these two species by combining information from comprehensive observational, experimental, GIS analysis and remote sensing data, deriving 65 variables to characterize the nest‐sites used and the breeding success in 381 breeding attempts over four consecutive breeding seasons. To assess interspecific and intraspecific territorial behaviour and aggressiveness, stuffed Long‐legged Buzzards and Short‐toed Eagles were presented close to nests. Nest‐site characteristics overlapped substantially between species, and Long‐legged Buzzards occupied 21% of all Short‐toed Eagle nests. Intraspecific aggression rates among Long‐legged Buzzards were higher than their interspecific aggression rates with Short‐toed Eagles and also higher than intraspecific aggression among Short‐toed Eagles. Long‐legged Buzzard and Short‐toed Eagle breeding densities (1.59 ± 0.11 and 2.96 ± 0.11 pairs per 10 km2, respectively) are likely to be the highest across their respective breeding distributions, with a maximum productivity of 0.96 ± 0.01 and 0.56 ± 0.05 (young fledged/breeding pair) for Long‐legged Buzzard and Short‐toed Eagle, respectively. Intraspecific interactions among both species play an important role in determining their breeding success and the spatial distribution of nesting sites. Our results suggest that interspecific competition over nesting sites and territories between both species, and the potential dominance of Long‐legged Buzzard, has both direct and indirect impacts on the spatial and demographic distribution of Short‐toed Eagles due to the recent establishment of Long‐legged Buzzard territories in the Judean breeding area.  相似文献   

2.
    
Janis Raines 《Zoo biology》2005,24(6):557-568
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3.
    
Migration is a significant event in the annual cycle of many avian species. During migration birds face many challenges, including unfamiliar foraging and refuge habitats, resulting in a much higher rate of mortality during migration than during other seasons of the year. Weather may significantly affect a bird's decision to initiate migration, the course and pace of migration, and its survival during migration. Each of these influences may impact the counts of migrating birds at geographical convergence zones or bottlenecks. It is important to quantify the effect of short‐term weather on these counts to appropriately interpret and use such counts in other analyses. To this end, we aim to assess the effects of local and regional weather conditions on the migration counts of soaring birds at the Strait of Gibraltar during post‐breeding migration. We used information‐theoretic approaches to analyse the influence of local weather and weather in northern Spain on the migration counts of five soaring bird species from two count sites near the Strait of Gibraltar. Migration counts were higher on days with local northerly and westerly winds, often following a day of easterly winds, on days with local high pressure systems, and often following a day of lower pressure. Weather conditions in northern Spain influenced migration counts at the Strait of Gibraltar, but the effects were much weaker than local weather conditions. We confirm that short‐term weather conditions, locally and regionally, can influence migration counts and should thus be considered when these counts are used in other analyses.  相似文献   

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Capsule A five-year monitoring study is described of overall population stability and differential reproductive success in relation to habitat heterogeneity.

Aims To assess the effect of the altitude and orientation on laying date and breeding performance, and analyse the effect of territory quality as a likely factor that could be regulating the population.

Methods We monitored a population of 28–33 pairs, from 2002 to 2006, counting a total of 131 breeding attempts.

Results Territories located at lower altitude showed higher mean fecundity than those located at higher altitude. The mean laying date was February 18 ± 16 days. Laying date was positively correlated with nest altitude, the coastal pairs laying earlier than those in mountainous regions. Pairs located at lower altitudes showed higher mean fecundity than those located at higher altitudes. There was no preference in mean orientation either in breeding performance or in relationship to nest altitude. We did not find a difference in breeding performance between territories classed as being at high density and those classed as being at low density.

Conclusion The population has remained stable since the first national census was conducted 17 years ago. Our results could be explained in the light of the Habitat Heterogeneity Hypothesis. We suggest a differential reproductive success in relation to habitat heterogeneity.  相似文献   

6.
    
Gaps in our knowledge of the geographical distribution of species represent a fundamental challenge to biogeographers and conservation biologists alike, and are particularly pervasive in the tropics. Here we highlight the case of the Rufous‐thighed Kite Harpagus diodon, a South American raptor commonly mapped as resident across half the continent. Recent observations at migration watch points have indicated it may be partially migratory in the southernmost parts of its range. To investigate this possibility, we collated contemporary and historical specimen records, published sight records and ‘digital vouchers’ – photographs and sound‐recordings archived online (from citizen science initiatives) – and explored the spatiotemporal distribution of records. We were unable to trace any documented records of this species from Amazonia during the austral summer (October–March), or records from the Atlantic Forest biome during the peak of the Austral winter (June–August), and all proven breeding records stem from the Atlantic Forest region. We compared this pattern with that of a ‘control’ species, the congeneric Double‐toothed Kite H. bidentatus, again using specimens and digital vouchers. For this species we found no evidence of seasonality between biomes and can disregard spatiotemporal variation in observer effort as a cause of seasonal biases. We consider that all populations of Rufous‐thighed Kites are fully migratory, wintering in Equatorial forests in the Amazonian basin. We provide evidence that this pattern was previously obscured by erroneous undocumented records and poor or erroneous specimen metadata, and its discovery was primarily facilitated by digital vouchers. This discovery requires a reassessment of the species’ global conservation status as an Atlantic Forest breeding endemic, threatened by habitat loss and degradation, as it was previously considered to be resident across large swathes of undisturbed Amazonian Forest on the Guiana Shield. The bulk of the digital voucher data used to elucidate this pattern were extracted from a Brazilian citizen science initiative WikiAves, which may serve as a model for collating biodiversity data in megadiverse countries and help catalyse environmental awareness.  相似文献   

7.
基于文献、标本馆数据和野外调查记录, 共收集四川省猛禽分布记录数据2,410条, 依此分析了四川省猛禽的分布与迁徙路线。四川省猛禽记录有56种(76种及亚种), 其中隼形目3科41种, 占全国隼形目鸟类总数的64.06%; 鸮形目2科15种, 占全国鸮形目鸟类总数的48.39%; 国家I级重点保护猛禽5种。四川省猛禽总体呈现西部多东部少的格局, 记录最多的平武县有32种; 在垂直分布上以1,000-3,500 m海拔段物种丰富度最高。在四川省境内具有迁徙习性的猛禽有19种, 其中金堂县迁徙猛禽最多。主要迁移路线有3条: 1条属于中亚-印度迁徙路线, 经过四川省西北角的石渠和德格县; 另外2条属东亚-澳大利亚迁徙路线, 其中1条沿四川省盆地西缘的岷山-邛崃山-凉山一线向南到我国云南、缅甸; 另外1条沿四川北部岷山至金堂和南充一线向东南至重庆、贵州。本研究为保护四川猛禽资源和了解猛禽迁徙路线提供了参考。  相似文献   

8.
For animals that travel in groups, the directional choices of conspecifics are potentially a rich source of information for spatial learning. In this study, we investigate how the opportunity to follow a locally experienced demonstrator affects route learning by pigeons over repeated homing flights. This test of social influences on navigation takes advantage of the individually distinctive routes that pigeons establish when trained alone. We found that pigeons learn routes just as effectively while flying with a partner as control pigeons do while flying alone. However, rather than learning the exact route of the demonstrator, the paired routes shifted over repeated flights, which suggests that the birds with less local experience also took an active role in the navigational task. The efficiency of the original routes was a key factor in how far they shifted, with less efficient routes undergoing the greatest changes. In this context, inefficient routes are unlikely to be maintained through repeated rounds of social transmission, and instead more efficient routes are achieved because of the interaction between social learning and information pooling.  相似文献   

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Migration is costly in terms of time, energy and safety. Optimal migration theory suggests that individual migratory birds will choose between these three costs depending on their motivation and available resources. To test hypotheses about use of migratory strategies by large soaring birds, we used GPS telemetry to track 18 adult, 13 sub‐adult and 15 juvenile Golden Eagles Aquila chrysaetos in eastern North America. Each age‐class had potentially different motivations during migration. During spring, the migratory performance (defined here as the directness of migratory flight) of adults was higher than that of any other age‐classes. Adults also departed earlier and spent less time migrating. Together, these patterns suggest that adults were primarily time‐limited and the other two age‐classes were energy‐limited. However, adults that migrated the longest distances during spring also appeared to take advantage of energy‐conservation strategies such as decreasing their compensation for wind drift. During autumn, birds of all age‐classes were primarily energy‐minimizers; they increased the length of stopovers, flew less direct routes and migrated at a slower pace than during spring. Nonetheless, birds that departed later in autumn flew more directly, indicating that time limitations may have affected their decision‐making. During both seasons, juveniles had the lowest performance, sub‐adults intermediate performance and adults the highest performance. Our results show age‐ and seasonal variation in time and energy‐minimization strategies that are not necessarily exclusive of one another. Beyond time and energy, a complex suite of factors, including weather, experience and navigation ability, influences migratory performance and decision‐making.  相似文献   

10.
    
Site fidelity to breeding and wintering grounds, and even stopover sites, suggests that passerines are capable of accurate navigation during their annual migrations. Geolocator‐based studies are beginning to demonstrate precise population‐specific migratory routes and even some interannual consistency in individual routes. Displacement studies of birds have shown that at least adult birds are capable of goal‐oriented movements, likely involving some type of map or geographic position system. In contrast, juveniles on their first migration use a clock‐and‐compass orientation strategy, with limited knowledge about locations along their migratory routes. Positioning information could come from a variety of cues including visual, olfactory, acoustic, and geomagnetic sources. How information from these systems is integrated and used for avian navigation has yet to be fully articulated. In this review, we (1) define geographic positioning and distinguish the types of navigational strategies that birds could use for orientation, (2) describe sensory cues available to birds for geographic positioning, (3) review the evidence for geographic positioning in birds and methods used to collect that evidence, and (4) discuss ways ornithologists, particularly field ornithologists, can contribute to and advance our knowledge of the navigational abilities of birds. Few studies of avian orientation and navigation mechanisms have been conducted in the Western Hemisphere. To fully understand migratory systems in the Western Hemisphere and develop better conservation policies, information about the orientation and navigation mechanisms used by specific species needs to be integrated with other aspects of their migration ecology and biology.  相似文献   

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Birds that repeatedly visit distinct places along their migratory routes in consecutive years must be able to navigate to these places and respond appropriately to unfavourable wind conditions. This study analysed the migratory routes, repeatedly-visited areas and responses to sidewinds of 15 GPS-tracked adult ospreys Pandion haliaetus from northeast Germany migrating to their wintering sites in Africa and back. We determined stopovers and intermediate goal areas and performed repeatability estimations on timing and migratory paths in four regions. The orientation behaviour of the ospreys was analysed with regard to perpendicular wind components at each GPS point during autumn and spring migrations. Generalised linear mixed models were used to test the dependence of orientation behaviour on region and the distance to the next goal. The findings showed that ospreys demonstrate high fidelity to migratory paths in autumn and spring, as well as to the timing of migration in autumn; and sidewinds are predominantly compensated, especially when sidewinds are strong. Furthermore, during autumn migration, the proportion of compensation increases in most regions with decreasing distances to the next goal; however, during spring migration, drift behaviour was detected more often at smaller distances to the next goal than at higher distances in the regions Mediterranean and central Europe. In general, ospreys compensate for unfavourable sidewinds and utilise supporting tailwinds on their journeys to the wintering sites in Africa and back to central Europe.  相似文献   

12.
    
1.  In a seasonal environment, subcutaneous energy reserves of resident animals often increase in winter and decline again in summer reflecting gradual seasonal changes in their fattening strategies. We studied changes in body reserves of wintering great tits in relation to their dominance status under two contrasting temperature regimes to see whether individuals are capable of optimizing their body mass even under extreme environmental conditions.
2.  We predicted that dominant individuals will carry a lesser amount of body reserves than subordinate great tits under mild conditions and that the body reserves of the same dominant individuals will increase and exceed the amount of reserves of subordinates under conditions of extremely low ambient temperatures, when ambient temperature dropped down to −37 °C.
3.  The results confirmed the predictions showing that dominant great tits responded to the rising risk of starvation under low temperatures by increasing their body reserves and this was done at the expense of their safety.
4.  Removal experiments revealed that lower body reserves of subordinate flock members are due to the increased intraspecific competition for food under low ambient temperatures.
5.  Our results also showed that fattening strategies of great tits may change much quicker than previously considered, reflecting an adaptive role of winter fattening which is sensitive to changes in ambient temperatures.  相似文献   

13.
We describe primers and polymerase chain reaction conditions to amplify 17 di‐, tri‐ and tetranucleotide microsatellite loci from the three‐toed woodpecker (Picoides tridactylus). The primers were tested on 26 to 30 individuals from a single population breeding in southern Finland. The developed primer pairs yielded an average of 7.6 alleles per locus (range two to 15), an average observed heterozygosity of 0.69 (range 0.07 to 0.97), and an average polymorphic information content of 0.68 (range 0.06 to 0.90).  相似文献   

14.
    
While the impact of introduced predators is a widely acknowledged issue and key component of conservation considerations for endemic waterbird populations in the Hawaiian Islands, the impact of native predators on endemic, endangered waterbirds is not as frequently discussed or factored into recovery models. The Pueo (Hawaiian Short-eared Owl; Asio flammeus sandwichensis) is a subspecies of Short-eared Owl endemic to the Hawaiian Islands and is State-listed as Endangered on the island of O'ahu. The Ae'o (Hawaiian Stilt; Himantopus mexicanus knudensi) is a subspecies of the Black-necked Stilt endemic to Hawai'i and is federally listed as Endangered throughout its range. A variety of non-native predators are confirmed to consume Ae'o eggs, chicks, and adults, including invasive mammals (e.g., feral cats), birds (e.g., Barn Owls), and amphibians (e.g., bullfrogs). While predation by native predators was suspected, there are no cases documented in the literature to date describing Pueo preying upon Ae'o. Here, we describe four events that provide evidence of Pueo predating Ae'o during the 2019–2021 breeding seasons in a wetland area on the island of O'ahu: (1) confirmed Pueo predating an Ae'o chick, (2) a suspected predation attempt of a Pueo chasing adult Ae'o, and (3) two suspected predation events based on (a) 10 adult-sized Ae'o carcasses and remains found near an active Pueo nest and (b) game camera photos of Pueo visiting two Ae'o nests. To our knowledge, these novel observations are the first published accounts of predator–prey interactions between these two subspecies.  相似文献   

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16.
Understanding the functional links between social structure and population processes is a central aim of evolutionary ecology. Multiple types of interactions can be represented by networks drawn for the same population, such as kinship, dominance or affiliative networks, but the relative importance of alternative networks in modulating population processes may not be clear. We illustrate this problem, and a solution, by developing a framework for testing the importance of different types of association in facilitating the transmission of information. We apply this framework to experimental data from wild songbirds that form mixed-species flocks, recording the arrival (patch discovery) of individuals to novel foraging sites. We tested whether intraspecific and interspecific social networks predicted the spread of information about novel food sites, and found that both contributed to transmission. The likelihood of acquiring information per unit of connection to knowledgeable individuals increased 22-fold for conspecifics, and 12-fold for heterospecifics. We also found that species varied in how much information they produced, suggesting that some species play a keystone role in winter foraging flocks. More generally, these analyses demonstrate that this method provides a powerful approach, using social networks to quantify the relative transmission rates across different social relationships.  相似文献   

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A recently developed radar‐based technique permitted empirical re‐evaluation of the established but poorly supported theory that migrating North American waterfowl (Anatidae) use landscape features such as rivers as leading lines. Ducks departing the Illinois River Valley in the autumn of each of 15 years travelled SSE with a mean track that was 68° different from the 220° course of the Illinois River (P ≤ 0.001). We conclude that leading lines were unimportant navigation aids for ducks leaving this major stopover site in autumn and suggest that rivers have less effect on the spatial course of duck migration than previously thought. Timing of departures was examined in a representative subset of 8 years and found to be consistent, with a mean start time of 44 min after civil sunset.  相似文献   

20.
    
Migrant species are commonly thought to be poor competitors in aggressive interactions with resident species. However, no studies have tested whether this relationship is widespread. Here, we compare the behavioural dominance of closely related species of migratory and nonmigratory birds, testing whether migrants are consistently subordinate to resident species in aggressive contests. We compiled published behavioural dominance data involving migrant and resident congeners, gathering additional data on the body mass and migratory distance of each species. Focal species included a diverse array of birds (28 taxonomic families, 12 orders) from around the world. We found that migrant species are usually subordinate to resident species, but that this relationship disappears at larger body sizes. For smaller birds (<500 g), resident species were behaviourally dominant in 83%–88% of comparisons; for larger birds (>500 g), resident species were dominant in only 25%–30% of comparisons. The relative difference in body mass best predicted dominance relationships among species, with larger species dominant in 80%–84% of comparisons. When migrant and resident masses were equal, however, resident species were still more likely to be dominant in smaller birds, suggesting that other factors may also contribute to the subordinate status of migrants. Overall, our results suggest that in smaller species, the evolution of migration is associated with lighter weights and other traits that compromise the competitive abilities of migrants relative to residents. In contrast, larger species appear able to evolve migration without compromising their size or competitive abilities in aggressive contests, suggesting size‐dependent constraints on the evolution of migration.  相似文献   

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