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1.
Data concerning habitat characteristics and general physiographic characteristics at 29 Short-toed Eagle Circaetus gallicus nest-sites (circular plot of 0.4 ha centred on the nest tree) were collected and compared with the same number of paired randomly selected plots in Dadia-Lefkimi-Soufli forest complex, northeast Greece. Short-toed Eagles used southern slopes for nesting and nest-sites were often located on the upper third of each slope. Nest trees were found significantly closer to rain water gullies, to the boundary of a different habitat type, and to the nearest forest opening greater than 0.5 ha than the randomly selected nest trees. Nest-sites had a significantly lower mean score of human disturbance than random sites and were found in mature pine forest associations, dominated by Calabrian Pine Pinus brutia or Black Pine P. nigra. The total tree density of Short-toed Eagle nest-sites was lower than random sites. Canopy cover in the dominant and intermediate tree layer at nest-sites was lower than at random sites. Short-toed Eagles tended to select sites for nesting that provided a combination of easy access and maximum shelter of the nest content from predators and inclement weather. The preservation of open structure of mature pine stands on south facing slopes near clearings may be critical for the continued conservation of the Short-toed Eagle in actively managed forests, such as the Dadia-Lefkimi-Soufli forest complex.  相似文献   

2.
High concentrations of orangutans remain in the multiple-use forests of the Lower Kinabatangan, Sabah, Malaysia. Compared to primary forest, the habitat is highly fragmented, characterized by a low tree density (332 stems/ha), small tree size (83.6% of trees are <20 m high), low basal area (18 m2/ha), abundance of canopy gaps and high level of soil disturbance. The forest structure and composition influence orangutan nesting patterns, and thus directly influence the results of nest surveys used to determine orangutan population size. In logged forests, tall and large trees are the preferred nesting sites of orangutans. The scarcity of suitable nesting sites in the logged-over forests of Kinabatangan, could partly explain the lower daily rate of nest construction (r = 1.00) versus those of other orangutan populations. The nest decay rate t recorded at the study site (average ± SD = 202 ± 151 days) strongly depends on the species of tree in which a nest is built. Our results illustrate that the nest-related parameters used for orangutan censuses fluctuate among habitat types and emphasize the need to determine specific values of r for specific orangutan populations and of t for different tree species in order to achieve accurate analysis of census data.  相似文献   

3.
This paper reports on the tree structure, tree dimension relationships and woody biomass production and removal of a sub-tropical natural forest in the Mamlay watershed of the Sikkim Himalaya. The forest provides fuel, fodder and timber to four villages. Only 11 tree species were found growing in the tree stratum despite the high diversity in the stand (32 tree species). The forest shows good regeneration potential with 5474 seedlings/ha and 1776 saplings/ha, but the population structure revealed a marked paucity of trees of higher diameter classes due to removal of trees of lower diameters. Standing wood biomass of 362 Mg/ha is mainly shared by 4 dominating species in the stand. The boles are removed mainly for timber and fuel purposes and about 22 Mg/ha wood biomass was removed in between 1987–1991. Net Primary productivity of woody biomass of the forest is recorded to be 18 Mg/ha/year. 3.85 Mg/ha of annual woody biomass production was removed in the form of tree boles apart from lopping of branches.  相似文献   

4.
Success of species conservation depends to a large extent on comprehensive management that considers all critical aspects of a species’ niche. Many studies have examined habitat factors in relation to occurrence, abundance or foraging behaviour of European woodpecker species, while relatively little is known about nest site selection. I compared habitat structures used for nesting by middle and great spotted woodpeckers Dendrocopos medius and D. major with available structures in an oak forest in the Swiss lowlands. I first tested if nest trees were randomly selected among available trees by focusing on species, condition and diameter of nest trees, and on the presence of the fruiting body (hereafter sporophore) of polypores (wood-decomposing fungi). Second, I examined if the nesting niches of the two species were differentiated. Both species showed strong preferences for oaks, large trees, dead trees and for trees with sporophores. Nest sites of the two species differed most strongly with respect to the presence of sporophores, cavity age and tree condition, pointing towards interspecific competition for nest sites. Old living or dead trees with sporophores are central components of the nesting niche of middle and great spotted woodpeckers. Conservation plans for the threatened middle spotted woodpecker have so far mostly focused on the needs in terms of distribution and foraging; future conservation strategies and forest management must take into account the preference for dead and decaying trees with sporophores as another vital resource. This will also provide benefits for other woodpecker species as well as for the community of secondary cavity nesters.  相似文献   

5.
ABSTRACT Within forests susceptible to wildfire and insect infestations, land managers need to balance dead tree removal and habitat requirements for wildlife species associated with snags. We used Mahalanobis distance methods to develop predictive models of white-headed woodpecker (Picoides albolarvatus) nesting habitat in postfire ponderosa pine (Pinus ponderosa)-dominated landscapes on the Fremont-Winema National Forests in south central Oregon, USA. The 1-km radius (314 ha) surrounding 45 nest sites was open-canopied before fire and a mosaic of burn severities after wildfire. The 1-ha surrounding nests of white-headed woodpeckers had fewer live trees per hectare and more decayed and larger diameter snags than at non-nest sites. The leading cause of nest failure seemed to be predation. Habitat and abiotic features were not associated with nest survival. High daily survival rates and little variation within habitat features among nest locations suggest white-headed woodpeckers were consistently selecting high suitability habitats. Management activities that open the forest canopy and create conditions conducive to a mosaic burn pattern will probably provide suitable white-headed woodpecker nesting habitat after wildfire. When making postfire salvage logging decisions, we suggest that retention of larger, more decayed snags will provide nesting habitat in recently burned forests.  相似文献   

6.
NIALL H. K. BURTON 《Ibis》2009,151(2):361-372
Aspects of the reproductive success of Tree Pipits Anthus trivialis were examined in relation to broad‐scale habitat and nest‐site selection in Thetford Forest, a coniferous plantation forest in eastern England. Three habitat classes were defined corresponding to previously reported densities of Tree Pipits: clearfell and recently planted stands (habitat class A: low density), stands 2–5 years old (B: high density) and stands 6 years or older (C: low density). The preference for 2–5‐year‐old stands indicated by higher densities was supported by the timing of territory settlement. Tree Pipits also showed distinct preferences for nest‐site characteristics that were relatively consistent across habitat classes and throughout the breeding season. At the ‘habitat scale’, results were consistent with the predictions of the ideal despotic distribution model. First clutches were laid significantly earlier in the preferred habitat class B. Overall nesting success (i.e. the proportion of nests producing fledglings), but not clutch size, also varied between habitats, being greater in habitat classes B and C than in habitat class A. The variation in overall nesting success between habitats was primarily driven by low nest survival rates during the laying/incubation period in clearfell and recently planted stands. Nest survival rates during the nestling period were lower in the preferred 2–5‐year‐old (and older) stands and declined over the course of the study. Preferences for nest‐site characteristics (at least for those that were measured) provided no apparent benefit to nest survival rates. Overall nesting success thus appeared to be determined at the habitat scale, perhaps because the broad differences in cover between habitats affected the likelihood of nest predation (the main cause of nest failure). It is suggested that the very low nesting success experienced by Tree Pipits in clearfell and new stands may be one factor in the species’ relative avoidance of this habitat and preference for 2–5‐year‐old stands.  相似文献   

7.
Many studies have dealt with the habitat requirements of cavity‐nesting birds, but there is no meta‐analysis on the subject and individual study results remain vague or contradictory. We conducted a meta‐analysis to increase the available evidence for nest‐site selection of cavity‐nesting birds. Literature was searched in Web of Science and Google Scholar and included studies that provide data on the habitat requirements of cavity‐nesting birds in temperate and boreal forests of varying naturalness. To compare nest and non‐nest‐tree characteristics, the following data were collected from the literature: diameter at breast height (DBH) and its standard deviation (SD), sample size of trees with and without active nest, amount of nest and available trees described as dead or with a broken crown, and amount of nest and available trees that were lacking these characteristics. Further collected data included bird species nesting in the cavities and nest‐building type (nonexcavator/excavator), forest type (coniferous/deciduous/mixed), biome (temperate/boreal), and naturalness (managed/natural). From these data, three effect sizes were calculated that describe potential nest trees in terms of DBH, vital status (dead/alive), and crown status (broken/intact). These tree characteristics can be easily recognized by foresters. The results show that on average large‐diameter trees, dead trees, and trees with broken crowns were selected for nesting. The magnitude of this effect varied depending primarily on bird species and the explanatory variables forest type and naturalness. Biome had lowest influence (indicated by ΔAIC). We conclude that diameter at breast height, vitality, and crown status can be used as tree characteristics for the selection of trees that should be retained in selectively harvested forests.  相似文献   

8.
Animals are expected to select a breeding habitat using cues that should reflect, directly or not, the fitness outcome of the different habitat options. However, human‐induced environmental changes can alter the relationships between habitat characteristics and their fitness consequences, leading to maladaptive habitat choices. The most severe case of such nonideal habitat selection is the ecological trap, which occurs when individuals prefer to settle in poor‐quality habitats while better ones are available. Here, we studied the adaptiveness of nest box selection in a tree swallow (Tachycineta bicolor) population breeding over a 10‐year period in a network of 400 nest boxes distributed along a gradient of agricultural intensification in southern Québec, Canada. We first examined the effects of multiple environmental and social habitat characteristics on nest box preference to identify potential settlement cues. We then assessed the links between those cues and habitat quality as defined by the reproductive performance of individuals that settled early or late in nest boxes. We found that tree swallows preferred nesting in open habitats with high cover of perennial forage crops, high spring insect biomass, and high density of house sparrows (Passer domesticus), their main competitors for nest sites. They also preferred nesting where the density of breeders and their mean number of fledglings during the previous year were high. However, we detected mismatches between preference and habitat quality for several environmental variables. The density of competitors and conspecific social information showed severe mismatches, as their relationships to preference and breeding success went in opposite direction under certain circumstances. Spring food availability and agricultural landscape context, while related to preferences, were not related to breeding success. Overall, our study emphasizes the complexity of habitat selection behavior and provides evidence that multiple mechanisms may potentially lead to an ecological trap in farmlands.  相似文献   

9.
Parrot populations are being increasingly pressured to occupy modified or fragmented landscapes, yet little is known of the habitat requirements of most species, particularly with regard to the effects on breeding habitat. We evaluated nesting habitat of the lilac-crowned parrot Amazona finschi in the modified landscape of coastal Michoacan in Mexico. We located 90 parrot nests in 12 tree species in Michoacan, with lilac-crowned parrots presenting a narrow niche-breadth of tree species used for nesting. Considering an additional 82 nest trees recorded for lilac-crowned parrots in Jalisco, we determined a 51 percent similarity in cavity resource use by parrots in the two dry forest regions. Overall, the predominant nest tree species with 76 percent of nests were Astronium graveolens , Piranhea mexicana , Brosimum alicastrum , and Tabebuia spp., all characteristic of semi-deciduous forest. Only 8 percent of nests occurred in trees characteristic of deciduous forest. Parrots utilized large trees with canopy level cavities as nest sites, and preferred conserved semi-deciduous forest for nesting, with fewer nests than expected in deciduous forest and transformed agricultural land. Nest areas in semi-deciduous forest occurred on significantly steeper terrain, as remnant semi-deciduous forest is restricted to steep ridges and canyons. Those parrot nests in modified habitats and forest patches were located near to continuous forest, with nest trees in open agricultural land being significantly closer to continuous forest than nests in disturbed forest patches. These results demonstrate the importance of conserved semi-deciduous forest as breeding habitat for the threatened, endemic lilac-crowned parrot, making wild populations of the species vulnerable to the high rate of transformation and fragmentation of tropical dry forest.  相似文献   

10.
ABSTRACT Species in the family Psittacidae may be particularly vulnerable to anthropogenic habitat transformations that reduce availability of suitable breeding sites at different spatial scales. In southern Chile, loss of native forest cover due to agricultural conversion may impact populations of Slender‐billed Parakeets (Enicognathus leptorhynchus), endemic secondary cavity‐nesting psittacids. Our objective was to assess nest‐site selection by Slender‐billed Parakeets in an agricultural‐forest mosaic of southern Chile at two spatial scales: nest trees and the habitat surrounding those trees. During the 2008–2009 breeding seasons, we identified nest sites (N= 31) by observing parakeet behavior and using information provided by local residents. Most (29/31) nests were in mature Nothofagus obliqua trees. By comparing trees used for nesting with randomly selected, unused trees, we found that the probability of a tree being selected as a nest site was positively related to the number of cavity entrances, less dead crown, and more basal injuries (e.g., fire scars). At the nesting‐habitat scale, nest site selection was positively associated with the extent of basal injuries and number of cavity entrances in trees within 50 m of nest trees. These variables are likely important because they allow nesting parakeets to minimize cavity search times in potential nesting areas, thereby reducing energetic demands and potential exposure to predators. Slender‐billed Parakeets may thus use a hierarchical process to select nest sites; after a habitat patch is chosen, parakeets may then inspect individual trees in search of a suitable nest site. Effective strategies to ensure persistence of Slender‐billed Parakeets in agricultural‐forest mosaics should include preservation of both individual and groups of scattered mature trees.  相似文献   

11.
Capsule: Tawny Owls Strix aluco occupying nest boxes preferred habitats which were positively associated with the probability of nesting success.

Aims: We aimed to determine whether or not: (1) Tawny Owls showed habitat preferences when occupying nest boxes; (2) nesting performance was related to the habitats around occupied nest boxes and (3) habitat availability had changed around available and occupied nest boxes between 1995–2004 and 2005–14.

Methods: Tawny Owls were studied using nest boxes erected in a commercial forest. During nest boxes checks (724 cases), data on occupancy and nesting performance (88 cases) were recorded, and habitat within a 0.4?km radius around nest boxes was analysed.

Results: Tawny Owls had preferences for clearings within forests, mature forests and grasslands but avoided young forests. We found a positive relationship between nesting success and abundance of clearings within the forest, and a negative relationship between nesting success and abundance of young forests. A change in habitat preferences over the two decades was evident, but habitat availabilities remained similar.

Conclusions: Findings indicate adaptive habitat selection in Tawny Owls because preferred habitats were associated with higher fitness and this type of habitat became more frequently selected over time.  相似文献   

12.
We examined the patterns of habitat use of six radio-tagged booted eagles (Hieraaetus pennatus) in a Special Protection Area (SPA) in southeastern Spain. Variable percentages of radio locations (20.8–72.0 %) and home range areas (45.2–81.3 %) lay outside the SPA limits. A model selection procedure showed that habitat use was mainly influenced by habitat type and the distance to the nest. Edges and open lands were the most selected habitat types at long distances, while the probability of forest use strongly decreased with the distance. We conclude that effective conservation strategies for this species should encourage not only the protection of the forest nesting habitats, but also the traditional agricultural practices of the surrounding agroecosystems.  相似文献   

13.
Identifying habitat or nesting microhabitat variables associated with high levels of nest success is important to understand nest site preferences and bird–habitat relationships. Little is known about cavity availability and nest site requirements of cavity nesters in southern hemisphere temperate forests, although nest site limitation is suggested. Here we ask which characteristics are selected by the Austral parakeet (Enicognathus ferrugineus) for nesting in Araucaria araucana–Nothofagus pumilio forest in Argentine Patagonia. We compared nest plot and tree characteristics with unused plots and trees among areas of different A. araucana–N. pumilio density. We also examine whether nest plot and tree use and selection, and the associated consequences for fitness of Austral parakeets are spatially related to forest composition. Austral parakeets showed selectivity for nests at different spatial scales, consistently choosing isolated live and large trees with particular nest features in a non‐random way from available cavities. Mixed A. araucana–N. pumilio forests are ideal habitat for the Austral parakeets of northern Patagonia, offering numerous potential cavities, mainly in N. pumilio. We argue that Austral parakeet reproduction and fitness is currently very unlikely to be limited by cavity availability, although this situation may be rapidly changing. Natural and human disturbances are modifying south temperate forests with even‐aged mid‐successional stands replacing old growth forests. Cavity nesting species use and need old growth forests, due to the abundance of cavities in large trees and the abundance of larvae in old wood. Neither of the latter resources is sufficiently abundant in mid‐successional forests, increasing the vulnerability and threatening the survival of the Austral.  相似文献   

14.
ABSTRACT Northern bobwhite (Colinus virginianus) is a species for which extensive knowledge exists regarding its ecology, life history, and habitat. Although the qualitative aspects of bobwhite habitat have been described and known for many decades, researchers have neglected to characterize bobwhite habitat quantitatively (i.e., habitat selection). Thus, biologists have been capable of identifying components that compose bobwhite habitat but have only been able to speculate on how much of each component was necessary. We documented selection-avoidance behavior of nesting bobwhites in Brooks County, Texas, USA, during May-August, 2004–2005. We measured 5 vegetation features (i.e., nesting-substrate ht and width, suitable nest clump density, herbaceous canopy coverage, and radius of complete visual obstruction) at nest sites (n = 105) and at random points (n = 204). We used continuous selection functions to assess habitat use and identify bounds of suitability. Selection domains for nesting-substrate height and radius of complete visual obstruction were 16.9–31.2 cm and 1.05-4.35 m, respectively. Across all measurements, bobwhites selected for nest sites with a nesting-substrate width ≥22.4 cm, suitable nest-clump density ≥730 nest clumps/ha, and herbaceous canopy coverage ≥36.7%. This knowledge will provide an important foundation for managers to evaluate current nesting conditions on semiarid rangelands and provide a basis for habitat management aimed at creating suitable nesting habitat for bobwhites.  相似文献   

15.
Summary The aerial nests ofVespa affinis on Ishigaki Island, Japan, were found mainly within 1 m of the ground, attached to a twig roughly 4 mm in diameter. These are probably adaptations to survive adverse weather conditions. The favoured nesting habitat was in open farmland areas rather than in the natural forest. The entire envelope and more than half of the comb of the embryo nest is constructed during the first 10–12 days. The first workers emerge around 34 days after nest initiation. The duration of larval development was found to be linked to the number of larvae present in the nest, with the earlier progeny developing faster. The changes in the ovarian index of the mother queen during the early stages of nesting are described.  相似文献   

16.
岷山黑熊生境选择的初步分析   总被引:23,自引:1,他引:22  
鲁庆彬  胡锦矗 《兽类学报》2003,23(2):98-103
1998 年3 月末至9 月, 作者在岷山山系对黑熊的生境选择进行了研究。野外工作中共设置了40 个20 ×20 m2样方和15 个生态因子, 以此为基准进行了定量分析。黑熊生境喜好程度分析表明, 黑熊喜欢选择向阳、坡度较大、避风性适中、郁闭度在30 %~50 %之间的山嵴或山坡面, 选择乔木密度和灌木密度适中、倒木密度和树桩密度较小的生境, 其他如乔木距离、灌木距离、倒木距离和树桩距离以适中为准。主成分分析表明,影响黑熊生境选择的主要因子有5 种, 依次为: 食物丰富度因子(包括乔木密度、灌木密度、乔木距离和灌木距离) 、干扰因子(包括倒木密度、树桩密度、倒木距离和树桩距离) 、地形因子(包括郁闭度、地理性和坡位) 、气候因子(包括避风性和坡向) 和海拔因子。其最适生境状况为: 乔木密度为1 226~1 625根/ hm2, 灌木密度为1 425~1 976 根/ hm2, 倒木密度为120~240 根/ hm2 , 树桩密度为110~230 根/ hm2 , 郁闭度为3519 %~4315 % , 地理性为0.6~0.7 (山坡面) , 坡位为0.5~0.7 (中坡位) , 避风性为0.4~0.7 (适中) , 坡向为49.8°~153°(东坡) , 海拔高度为1 993~2 276 m (阔叶林和针阔混交林带) 。  相似文献   

17.
Wood ants are a dominant and ecologically important component of northern coniferous forests with interactions at many trophic levels. Each species exhibits specific habitat preferences which need to be understood if conservation measures are to be successful. In Britain, the rare narrow-headed ant Formica exsecta has disappeared from much of its former range and is now largely restricted to the highlands of Scotland where it is found in open canopy woodland and along forest edges. Nest locale of one small and vulnerable population at the edge of its current range, were compared with those of random locations within the same habitat and with actual nests within the stronghold of the Abernethy-Glenmore complex in Strathspey. After data exploration with Redundancy Analysis, stepwise multiple regression was used to create a model which best estimated the variance in nest location using a parsimonious selection of vegetation and environmental variables. The input variables included were light, soil moisture, altitude, tree stature and distribution, vegetation structure and composition, and ground characteristics. F. exsecta clearly exhibited preferences for the position of nest mounds in relation to light, vegetation and tree cover. Forest location was also important in determining which variables nests were affected by. This study highlights the importance of maintaining a dynamic mosaic of different-aged woodland enabling early successional species such as F. exsecta, with suitable areas to move to as conditions change and allowing the co-existence of all wood ant species.  相似文献   

18.
This paper reports on the nesting ecology of blue-and-yellow macaws (Ara ararauna) and the structure, conservation, and management of the Mauritia flexuosa palm swamps where they nest: clutch size averaged 2.6 and the number of chicks fledged per nesting attempt was 0.5. Macaws nested in tall dead palms in healthy palm swamps and in palms of all heights in open dieing palm stands. All nesting palms rose well above the surrounding vegetation presumably to discourage terrestrial predators. PVC nest boxes failed to attract nesting blue-and-yellow macaws. A small section of palm swamp was managed to encourage macaw nesting by cutting the tops off of M. flexuosa palms and clearing the understory vegetation. The palms remained standing from 4 to 7 years and were occupied by nesting macaws at a rate of 24%. The data presented here suggest that cutting five palms a year in perpetuity would produce a stand of approximately 20 standing dead palms used by 6 or more pairs of macaws annually. However, macaw occupancy rates would depend on the density of macaws and density of naturally occurring nest sites. This management scheme could be conducted on a 100-year rotation in an area of 1–4 ha or more depending on the palm density. Such a colony could be used to increase reproductive success of blue-and-yellow macaw populations, create a valuable ecotourism resource, and concentrate macaw nesting in protected areas.  相似文献   

19.
Anthropogenic habitat loss and fragmentation affect populations worldwide. For example, many bird populations of boreal forests have declined due to intensive forestry. To target conservation actions for such species, determining the key factors that affect their habitat selection is essential. Remote sensing methods provide highly potential means to measure habitat variables over large areas. We aim at identifying the key‐features of habitats by utilizing remote sensing data. As a case example, we study the nest site selection of a primary hole‐nesting passerine, the willow tit Poecile montanus, in a managed forest landscape. Using presence–absence data, we determine the most important habitat characteristics of the nest sites for three spatial scales by generalized linear mixed effect models. Our results highlight the importance of the availability of nesting sites – standing decaying deciduous trees – in the nest site selection of P. montanus. It seems to prefer moist habitats with high densities of deciduous trees and to avoid open areas, but does not require mature or intact habitats. Most of the nest site selection seems to occur within small scales. In this case, remote sensing data alone was insufficient for producing reliable models, but adding information of an ecologically important feature from direct field surveys greatly improved model performances. For the conservation and maintenance of dead wood dependent species, changes in forestry practices are necessary to keep the key characteristics of the habitat. Most importantly, continuous availability of standing decaying wood should be secured.  相似文献   

20.
The effects of habitat fragmentation as a threat to biodiversity are well known; decreased connectivity can potentially influence population processes and dynamics, resulting in smaller, isolated populations that may not function optimally. However, fragmentation may also increase the amount of edge or ecotone habitat available to open country species, benefiting their populations and enabling them to dominate remnant habitats. Noisy miners (Manorina melanocephala) are one such species, occupying eastern‐Australian eucalypt woodlands. They are considered a ‘despotic’ species, in that their presence negatively impacts woodland avifauna biodiversity due to their aggressive exclusion of other taxa from occupied areas. Despite this well‐known impact, little information exists on the patterns of nest‐tree occupancy by noisy miners within eucalypt woodlands. In the current study, we explored the patterns of nest‐tree occupancy by noisy miners across two successive years, aiming to identify preferences for breeding areas relative to vegetation structure. Our results show that both habitat fragmentation and the characteristics of individual eucalypt trees in an area influenced nest‐tree occupancy. Noisy miners constructed nests in trees near the edge of woodland patches more often than expected. Moreover, the nest tree chosen was a eucalypt that was significantly smaller than randomly selected trees from the surrounding area. The results highlight the importance of habitat management measures that may reduce the suitability of woodland patches as nesting sites for this species, in order to mitigate the severe effects of this despotic edge specialist.  相似文献   

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