Use of landscape metrics to predict avian nest survival in a fragmented midwestern forest landscape

Habitat fragmentation fundamentally affects trophic interactions and ecosystem function. Understanding how the landscape matrix modulates such interactions can improve our understanding of fragmentation ecology. Studies of breeding birds provide clear examples of the consequences of habitat fragmentation, but the landscape context of these effects are unclear. We sampled avian nesting success in 12 moderately-large forest patches (>250 ha) embedded in different types of landscapes in southern Illinois, USA. We then evaluated eight models that predicted the probability of nest success and brood parasitism by Brown-headed Cowbirds. These models incorporated landscape composition (% grassland, % agriculture, fragmentation), year and seasonal effects, conspecific density, predator density, and combinations of these variables. Temporal factors (stage of nesting cycle, seasonal effects, annual variation) had the most effect on nesting success; landscape factors had little influence on nesting success. The rate and intensity of brood parasitism were significantly influenced by the amount of grassland for the Wood Thrush, but not for the Acadian Flycatcher. Fine-scale management of the matrix surrounding the patches may dictate the local abundance and movements of nest predators and parasites. Other major nest predators may prefer the forest interior and at least partially compensate for the lower abundance of nest predators that depend upon the matrix. Overall, landscape metrics were weak predictors of avian nesting success in complex landscapes that have diverse predator communities.     

Scattered trees are keystone structures - Implications for conservation

Scattered trees are prominent features in many landscapes worldwide, including natural landscapes, cultural landscapes, and recently modified landscapes. The ecological importance of scattered trees is widely acknowledged in natural landscapes, but has not been sufficiently appreciated in human-modified landscapes. This paper shows that scattered trees are keystone structures in a wide range of landscapes. At the local scale, ecological functions of scattered trees include: provision of a distinct microclimate; increased soil nutrients; increased plant species richness; increased structural complexity; and habitat for animals. At the landscape scale, ecological roles include: increased landscape-scale tree cover; increased connectivity for animals; increased genetic connectivity for tree populations; and provision of genetic material and focal points for future large-scale ecosystem restoration. Furthermore, in disturbed landscapes, scattered trees often are biological legacies that provide ecological continuity through time. In combination, these ecological functions support the argument that scattered trees are keystone structures. That is, their contribution to ecosystem functioning is disproportionately large given the small area occupied and low biomass of any given tree, and the low density of scattered trees collectively. Because scattered trees fulfill unique functional roles in a wide range of scattered tree ecosystems, their loss may result in undesirable ecological regime shifts. A key management challenge in all landscapes with scattered trees is to maintain a balance between recruitment and mortality of trees in an appropriate spatial pattern. Meeting this challenge may represent an important step towards the genuine integration of conservation and production in human-modified landscapes.     

Multi-scale factors affecting bird use of isolated remnant oak trees in agro-ecosystems

With recent emphasis on sustainable agriculture, conservation of native biota within agricultural systems has become a priority. Remnant trees have been hypothesized to increase biological diversity in agro-ecosystems. We investigated how remnant Oregon white oak (Quercus garryana) trees contribute to conserving bird diversity in the agro-ecosystem of the Willamette Valley, Oregon, USA. We compared bird use of isolated oak trees in three landscape contexts - croplands, pastures, and oak savanna reserves - and ranked the relative importance of four factors thought to influence bird use of individual trees: (i) tree architecture; (ii) tree isolation; (iii) tree cover in the surrounding landscape; and (iv) landscape context, defined as the surrounding land use. We evaluated species-specific responses and four community-level responses: (i) total species richness; (ii) richness of oak savanna-associates; (iii) tree forager richness; and (iv) aerial and ground forager richness. We documented 47 species using remnant oaks, including 16 species typically occurring in oak savanna. Surprisingly, landscape context was unimportant in predicting frequency of use of individual trees. Tree architecture, in particular tree size, and tree cover in the surrounding landscape were the best predictors of bird use of remnant trees. Our findings demonstrate that individual remnant trees contribute to landscape-level conservation of bird diversity, acting as keystone habitat structures by providing critical resources for species that could not persist in otherwise treeless agricultural fields. Because remnant trees are rarely retained in contemporary agricultural landscapes in the United States, retention of existing trees and recruitment of replacement trees will contribute to regional conservation goals.     

Improving the biodiversity benefits of hedgerows: How physical characteristics and the proximity of foraging habitat affect the use of linear features by bats

Within agricultural landscapes, linear features such as hedgerows and tree-lines provide valuable habitat for many species. We use data from 315 transects, completed as part of a national acoustic survey of bat distribution, to examine the incidence of four bat species adjacent to linear features in rural areas. The use of linear features was assessed in relation to hedgerow width, tree density, the presence of water and woodland proximity. To examine the effect of tree density, linear features were classified as either hedgerows without trees, hedgerows with sparse trees (comprising <50% tree canopy) or tree-lines (>50% tree canopy). The use of linear features by Pipistrellus pipstrellus was not affected by tree density; linear features of all types were associated with a similar increase in P. pipistrellus incidence. The use of linear features by Pipistrellus pygmaeus was dependent on both tree density and the proximity of woodland; only linear features containing trees provided an increase in P. pygmaeus incidence regardless of woodland proximity. P. pipistrellus and P. pygmaeus incidence was not affected by hedgerow width or the presence of water. Incidence of Nyctalus noctula and Eptesicus serotinus was unaffected by the density of linear features of any type. Many agri-environment schemes offer financial incentives for the creation and management of hedgerows. Optimising the biodiversity gain provided by linear features will maximise the effectiveness of these schemes. Agri-environment measures that encourage the provision and retention of hedgerow trees will benefit bats in agricultural landscapes.     

The role of nest sites in limiting the numbers of hole-nesting birds: A review

The breeding densities of many bird-species which nest in tree cavities are in some areas limited by shortage of sites. This is evident from circumstantial evidence in which the numbers of breeding pairs in different areas correlate with the numbers of local nest sites, or where changes in the numbers of nest sites resulting from natural processes or human action are followed by changes in the numbers of pairs. It is also shown experimentally, where nest site provision or removal has been followed by a corresponding change in breeding density.

When nest boxes were provided, they were often occupied in the same year, leading to an immediate rise in breeding density. This implied that surplus birds were available in the vicinity and able to take them up. In future years, pair numbers often increased further but eventually they levelled off. This implied that, at this higher level, other limiting factors came into play. Experiments on nest site provision thus provide examples of different factors acting successively to limit breeding density at different levels.

By constraining breeding density, shortage of nest sites not only prevents some birds from breeding, but must also limit the total numbers of breeders and non-breeders, because no population can increase beyond a certain point, when the production of young is limited. Once all available nest sites are occupied, reproduction is inevitably density-dependent with respect to the total population of breeders and non-breeders.

Because several bird species can use the same type of site, competition is frequent, and the numbers of dominant species can affect the numbers and distribution of others. In extreme situations, a species may be totally absent from areas where all suitable nest sites are occupied by dominant competitors. In less extreme situations, the numbers of a subordinate species may vary from year to year or from place to place in inverse relation to the numbers of a dominant species. Both these situations can be changed by the provision of extra sites.

In managed woods and modern tree plantations, most hole-nesting bird species are excluded or kept at extremely low levels by shortage of nest sites. This is a direct result of forestry practice, which usually entails removal of the old and dying trees that normally provide the sites. The problem can be rectified by allowing a number of old and dead trees to remain in managed forests, or (on a more local scale) by the provision of nest boxes. By appropriate design and positioning of the boxes, the most desired species can be favoured.     

Agricultural intensification and loss of matrix habitat over 23 years in the West Wimmera, south-eastern Australia

The global trend toward more intensive forms of agriculture is changing the nature of matrix habitat in agricultural areas. Removal of components of matrix habitat can affect native biota at the paddock and the landscape scale, particularly where intensification occurs over large areas. We identify the loss of paddock trees due to the proliferation of centre pivot irrigation in dryland farming areas as a potentially serious threat to the remnant biota of these areas. We used a region of south-eastern Australia as a case study to quantify land use change from grazing and dryland cropping to centre pivot irrigation over a 23-year period. We also estimated rates of paddock tree loss in 5 representative landscapes within the region over the same period. The total area affected by centre pivots increased from 0 ha in 1980 to nearly 9000 ha by 2005. Pivots were more likely to be established in areas which had originally been plains savannah and woodlands containing buloke (Allocasuarina luehmannii), a food source for an endangered bird. On average, 42% of paddock buloke trees present in 1982 were lost by 2005. In the two landscapes containing several centre pivots, the loss was 54% and 70%. This accelerated loss of important components of matrix habitat is likely to result in species declines and local extinctions. We recommend that measures to alleviate the likely negative impacts of matrix habitat loss on native biota be considered as part of regional planning strategies.     

Predicting reproductive success of insect- versus bird-pollinated scattered trees in agricultural landscapes

Scattered trees are set to be lost from agricultural landscapes within the next century without sustained effort to increase recruitment. Thus, understanding the reproductive dynamics of scattered tree populations will be critical in determining how they can contribute to population restoration. The distance between conspecifics should be a key predictor of reproductive success, as more isolated trees are expected to receive fewer pollinator visits and experience increased transfer of self-pollen during longer pollinator foraging bouts. Further, isolation effects should be greater in species with less mobile pollinators. Here we contrast the effects of plant isolation on reproductive success of two species of eucalypt “paddock trees”, Eucalyptus camaldulensis and Eucalyptus leucoxylon, with insect- and bird-pollination, respectively. Seed production was not affected by tree isolation in either the insect- or bird-pollinated species and once outliers were removed, neither was there an effect on germination rate. As somatic mutations may bias outcrossing rate estimates, we initially screened our microsatellite markers for mutations but found no variation in microsatellite profiles throughout the canopy of trees. Individual outcrossing rates did not decline with increasing tree isolation in either the insect- or bird-pollinated species, though there was considerable variation in these rates at large distances, suggesting that pollination becomes unreliable with increasing tree isolation. We found that pollination distances have likely increased in tree species in agricultural landscapes, and that this may be facilitated by introduced honeybees in the case of E. camaldulensis. We therefore suggest that even isolated trees of these species produce seed of sufficient quantity and quality to contribute to population restoration.     

Tallgrass prairie management and bird nest success along roadsides

The attributes of roadside vegetation, an important bird habitat in grassland ecosystems, have been shown to affect bird abundance, distribution composition, and diversity, yet there are relatively few works on reproductive success of birds nesting along roadsides. Because roadsides are linear habitats, management at the landscape scale can affect nest success in roadsides through bottom-up and top-down effects. In northeastern Oklahoma tallgrass prairie is subjected annually to prescribed spring fires. In the short term fires can alter both arthropod abundance and predator access to nests. We explored effects of burning on bird nest success with a five-year study along roads that traversed tallgrass prairie habitat. Using data from ∼1400 nests of 23 species, we generated nest survival curves for groups of altricial species defined by nest substrate (ground, shrub, tree, or culvert). We then determined if these curves were affected by management practice (spring burning), food abundance (arthropod biomass), and habitat attributes (tree density and height). Nest substrate had a large effect on nest success: despite their shorter nest exposure period, ground nests were least successful and culvert nests were most successful. An increase in arthropod biomass following burning was possibly the cause for the increased nest success in burned plots, regardless of substrate, suggesting bottom-up control. Tree height and nest height were correlated positively with nest success, whereas tree density had no effect. Conversely, nest predation rates were correlated negatively with nest success, with ground nests experiencing the highest predation, culvert nests the lowest. Our results suggest that burning may increase nest success through bottom-up processes, but some species may not benefit from the increase in food abundance as a result of a concomitant increase in predation.     

Health of remnant woodlands in fragments under distinct grazing regimes

Fragmented remnant woodlands in agricultural landscapes are of high conservation value world-wide. Many eucalypts in agricultural landscapes of Australia are in decline. We aimed to investigate nutrient enrichment as a process that may contribute to eucalypt decline. We studied remnant woodlands that had been exposed to distinct recent and current livestock grazing treatments: Currently Intense Grazed; Recently Intense Grazed (until 3 years ago); Recent Intermediate Grazed; and Recent Lightly Grazed by livestock. We assessed soil nutrient status and penetrability, eucalypt foliar nutrition and stable isotope ratios for N and C, attributes of understorey vegetation, and tree health. Soils of the Currently Intense Grazed treatment had high levels of ammonium and Colwell-P. Total N, P, C:N ratio and soil penetrability were generally high in Currently Intense Grazed and Recently Intense Grazed treatments relative to Recent Intermediate Grazed and Recent Lightly Grazed treatments. Foliar N, N stable isotope ratios, P and carbon stable isotope ratios (δ¹³C) were generally higher (less negative δ¹³C) in trees on Currently Intense Grazed and Recently Intense Grazed treatments than in trees on Recent Intermediate Grazed and Recent Lightly Grazed treatments. Soil surface litter, tall and low shrubs and rock were positively correlated with tree health. Grasses and eucalypt foliar N, P and δ¹³C were negatively correlated with tree health. Soil nutrient enrichment increased with increasing grazing intensity and was associated with increased weed invasion and with poor tree health that was in turn correlated to increased foliar N and P and less negative δ¹³C in woodland trees in this study. We argue that minimising soil nutrient enrichment of fragmented remnant woodlands is important, given the association of elevated soil nutrition with poor tree health, to ensure the persistence of eucalypts in agricultural landscapes.     

Water depth influences nest predation for a wetland-dependent bird in fragmented bottomland forests

The alteration and fragmentation of natural habitats has resulted in increased rates of nest predation and poor reproductive success for many bird species. The development of effective conservation strategies to reduce elevated rates of nest predation has been hindered by difficulties in fully understanding mechanisms underlying patterns and rates of nest predation in particular habitats. I recorded the outcome for 2726 nesting attempts of prothonotary warblers (Protonotaria citrea) breeding in fragmented bottomland forests and quantified the effect of nest predation on annual fecundity, determined the influence of different nest predators on rates of nest predation, and identified the factor driving rates of nest predation. There was a highly significant negative correlation between rates of nest predation and the actual annual reproductive output of prothonotary warblers. Of 1156 nest predation events, 73% were attributed to raccoons (Procyon lotor), 15% to snakes and 7% to southern flying squirrels (Glaucomys volans). Rates of nest predation decreased with increasing water depth as a result of nest predation by raccoons. Nests that were over water deeper than 60 cm were particularly successful. Habitat fragmentation, the draining of wetlands, and stream channelization may act synergistically to elevate rates of nest predation for those birds breeding in forested wetlands. Conservation actions designed to stop or reverse these processes will be especially beneficial to birds breeding in bottomland forest ecosystems.     

Resolving the urban nest predator paradox: The role of alternative foods for nest predators

Urbanization is a leading cause of species endangerment in the United States; however, certain species thrive in urban habitats. The loss of key predators or the addition of new predators in urban areas could alter the structure of urban communities. A reduction in nest predation is hypothesized to explain the high density of urban birds, yet urban areas typically have increased populations of avian nest predators. The loss of important nest predators in urban habitats, prey switching of urban predators, or successful nest defense against avian nest predators could explain this urban nest predator paradox. To assess these hypotheses I compared nest predation rates of Northern mockingbirds (Mimus polyglottos) in parking lots and residential neighborhoods to populations in pastures and wildlife preserves during 2007–2009 in Florida, USA and placed video cameras on a subset of nests in 2008–2009. Data do not support the hypothesis that urban nest predation rates are consistently lower than non-urban nest predation rates. Of the 56 nest predation events recorded, cats were the dominant urban predator and Cooper’s hawks (Accipiter cooperii) were the dominant non-urban predator. There was no evidence for a loss of important nest predators in urban habitats; however, prey switching by Cooper’s hawks likely occurred. There was also indirect evidence for the importance of nest defense. Furthermore, some of the cats recorded as nest predators in residential neighborhoods were owned cats and all but one cat predation event occurred at night. To reduce nest predation rates, cat owners should keep their cats indoors at night.     

REDUCING SHALLOW LANDSLIDE OCCURRENCE IN PASTORAL HILL COUNTRY USING WIDE‐SPACED TREES

Shallow landslides occur globally on soil‐mantled hilly and mountainous terrain. In New Zealand, they are a nation‐wide problem, particularly on pastoral hill country grazed by livestock. On these landscapes, trees are planted at low densities, often <70 stems per hectare (sph), to reduce landslide occurrence, but there has been limited quantification of their effectiveness in this role. This study determined the reduction in landslide occurrence at 65 sites planted with spaced trees (53 × Populus, 6 × Salix, 6 × Eucalyptus) following rainstorm events. Sites had a mean slope angle of 27 degrees and soils were predominantly silt or sand‐loams. Tree density across all sites was 32–65 sph, height was 8–43 m, canopy radius was 1–10 m and trunk diameter was 18–99 cm. Trees reduced landslide occurrence by 95 per cent compared to paired pasture control sites (0·4 per cent vs. 7·9 per cent scar area, respectively), and scars occurred on fewer sites with trees than pasture (10 vs. 45). For the 10 tree sites with scars, their area was <3·5 per cent, except at one site where it was 11·3 per cent. There were no significant differences between species in their effectiveness in reducing landslide occurrence. Analyses were partially successful in discriminating between sites with and without shallow landslides and identified some attributes with potentially useful discriminatory power. Aspect, mean slope angle and tree density did not feature significantly in the analyses because they were homogeneous across site groups. The study verified the large benefit from wide‐spaced tree planting on sites susceptible to shallow landslides. Copyright © 2011 John Wiley & Sons, Ltd.     

The disproportionate value of scattered trees

Scattered trees are declining in agricultural landscapes worldwide. They are considered keystone structures because their effect on ecosystem functioning is believed to be disproportionate relative to the small area occupied by any individual tree. We empirically demonstrate the disproportionate value of scattered trees for birds and bats in an Australian livestock grazing landscape. We surveyed birds at 108 sites and bats at 63 sites. Sites spanned the full range of tree densities in the study area, from zero to over 100 trees per hectare. The marginal value of individual trees was highest when trees occurred at low densities. Compared to treeless sites, bird richness doubled with the presence of the first tree; bat richness tripled with the presence of 3-5 trees; and bat activity increased by a factor of 100 with the presence of 3-5 trees. Thereafter, the marginal effect of additional trees on birds and bats diminished rapidly. Although specialist species were restricted to large areas of dense tree cover, scattered trees effectively maintained moderate levels of bird and bat activity throughout largely cleared parts of the landscape. Future management activities should recognize the disproportionate value of scattered trees.     

The role of remnant trees in seed dispersal through the matrix: Being alone is not always so sad

Remnant trees within the non-forest matrix are common structures of forest landscapes which have high conservation value due to their supposed roles as biological legacies and stepping stones in fragmented forest scenarios. Fleshy-fruited remnant trees are dispersal foci for many forest plants, as seeds accumulate under their canopies after visitation by forest frugivores. Despite this recognized effect, little is known about the relative role of remnant trees in maintaining their seed dispersal function after forest fragmentation. In this work, conducted in the Cantabrian Range (Northern Spain), seed deposition by frugivorous birds and post-dispersal seed predation by rodents were compared beneath the canopies of hawthorn (Crataegus monogyna) trees scattered in the non-forested matrix, to those embedded in forest patches. We studied two years which had strong differences in community-wide fruit abundance (high in 2004, and low in 2005). Hawthorn and holly (Ilex aquifolium) seeds dominated the seed rain. The density of dispersed seeds differed between years and tree type, with higher values under patch trees relative to remnant ones. However, the effect of tree type depended on both the year and the seed species, as larger differences were found in the year of high fruit availability, and with holly seeds. Higher levels of post-dispersal seed predation on holly seeds also contributed to offset the differences between tree types. Our results suggest that remnant trees, by functioning as dispersal foci, facilitate the dispersal of the two most abundant plant species for forest succession through the matrix. More importantly, we demonstrated that in years of low fruit availability in which forest frugivores are forced to exploit scattered fruit resources, the role of remnant trees may even be equivalent to that played by forest trees.     

Do Ural owls (Strix uralensis) suffer from the lack of nest sites in managed forests?

Nest site availability, preferences and quality for Ural owls (Strix uralensis) were studied in managed forests and a large nature reserve in Estonia. The owl's density was relatively higher in the reserve. Ural owls bred in tree cavities and stick nests, but preferred the cavities. Suitable cavities were very rare compared to stick nests, and most cavities were found in the reserve. Pairs having no suitable cavities in their territories started to breed less frequently, but no difference was detected in young produced per breeding attempt between cavity nests and stick nests. Used cavities and stick nests as well as unused stick nests were situated in similar stands and landscapes, but nest tree and nest characteristics of cavity nests were distinct. The study shows that in managed forests the lack of large snags and tree cavities may limit the numbers of Ural owls, which accept these structures for breeding more readily than stick nests. Retention of large cavity-forming trees in forestry operations may be an effective conservation strategy for this species.     

Density and success of bird nests relative to grazing on western Montana grasslands

Grassland birds are declining at a faster rate than any other group of North American bird species. Livestock grazing is the primary economic use of grasslands in the western United States, but the effects of this use on distribution and productivity of grassland birds are unclear. We examined nest density and success of ground-nesting birds on grazed and ungrazed grasslands in western Montana. In comparison to grazed plots, ungrazed plots had reduced forb cover, increased litter cover, increased litter depth, and increased visual obstruction readings (VOR) of vegetation. Nest density among 10 of 11 common bird species was most strongly correlated with VOR of plots, and greatest nest density for each species occured where mean VOR of the plot was similar to mean VOR at nests. Additionally, all bird species were relatively consistent in their choice of VOR at nests despite substantial differences in VOR among plots. We suggest that birds selected plots based in part on availability of suitable nest sites and that variation in nest density relative to grazing reflected the effect of grazing on availability of nest sites. Nest success was similar between grazed plots and ungrazed plots for two species but was lower for nests on grazed plots than on ungrazed plots for two other species because of increased rates of predation, trampling, or parasitism by brown-headed cowbirds (Molothrus ater). Other species nested almost exclusively on ungrazed plots (six species) or grazed plots (one species), precluding evaluation of the effects of grazing on nest success. We demonstrate that each species in a diverse suite of ground-nesting birds preferentially used certain habitats for nesting and that grazing altered availability of preferred nesting habitats through changes in vegetation structure and plant species composition. We also show that grazing directly or indirectly predisposed some bird species to increased nesting mortality. Management alternatives that avoid intensive grazing during the breeding season would be expected to benefit many grassland bird species.     

Evidence-based decisions on the use of predator exclosures in shorebird conservation

Conservation practitioners often rely on experience rather than scientific evidence when making management decisions. These experience-based measures can waste limited time and funding if the given conservation practice is ineffective. Unanalyzed conservation strategies may negatively impact the species that is being protected. The use of predator exclosures to increase hatching success in ground-nesting shorebirds has been studied for almost two decades, yet their effectiveness is still debated. In ecosystems where predation pressure is particularly strong, electrified exclosures have been adopted; however, there are no studies on their efficacy or potential negative impacts. We conducted a nest survival analysis for 10 years (1998-2007) of piping plover monitoring data to determine: 1) the effectiveness of predator exclosures and electrified predator exclosures, and 2) conditions associated with nest abandonments at electrified exclosures. We found that predator exclosures significantly increase nest hatching success. Electrified exclosures can also be very effective at increasing hatching success under certain conditions, but at sites with high human disturbance and red fox densities, the proportion of exclosed nests that are abandoned by parental adults becomes sizeable. The direct cause of nest abandonments remains unclear since fox behavior on beaches and the dynamics of foxes and plovers at exclosures have not been studied. Our results suggest that such information is necessary if conservation practitioners can make more informed use of this direct management measure.     

The use of artificial breeding chambers as a conservation measure for cavity-nesting procellariiform seabirds: a case study of the Madeiran storm petrel (Oceanodroma castro)

Procellariiform seabirds are amongst the most severely threatened taxa worldwide. Whilst the specific threats vary among species, problems such as introduced predators, loss of suitable nesting habitat and inter- and intra-specific competition for nest sites are common to many situations. This paper reports on an experiment to increase the availability of secure nest sites at a colony of Madeiran storm petrels breeding on an islet (free from introduced predators) in the Azores islands where there is evidence of inter-specific competition. The provision of nest boxes that were designed to exclude larger species led to around a 12% increase in the size of the breeding population in the first year and a 28% increase over the original colony size in the second year. Over three seasons, the breeding success of storm petrels nesting in boxes averaged 2.9 times greater than that of birds at natural sites, despite their likely reproductive inexperience. The techniques presented here should serve as a model for conservation management of other burrowing procellariiform species in situations where colony size or breeding performance is believed to be constrained by nest site quality.     

Status and conservation of the seychelles black parrot

A study of the Seychelles black parrot Coracopsis nigra barklyi, restricted to Praslin Island in the central Seychelles, was carried out between July and September 1976. A synchronised watch on 23 August provided an estimate for the total population of 90 birds ± 20,65% of which were in the Vallée de Mai region. Regular movements out of the Vallée between 0800 h and 0900 h and returning between 1700 h and 1800 h were noted, and these were associated with foraging. Most important food items during the study were Verschaffeltia splendida, an endemic palm, and the introduced Averrhoabilimbi. Breeding is probably concentrated in the period October to February, and it is thought that the lack of many suitable nest sites (standing rotting trees of Pandanus, Lodoicea, and Albizia) may be the major factor regulating numbers. The provision of suitable nest boxes, a policy of leaving dead Albizia and Acacia trees standing as nest sites, and the planting of fruit trees such as Verschaffeltia, Averrhoa and Ficus are suggested to help the conservation of the species.     

数字果树及其技术体系研究进展

果树是重要的农林植物。在万物智联时代,利用数字化、智能化、网络化技术建立数字果树技术体系,实现对果树生命、生产和生态复杂系统的高效感知、认知和智慧管控,对于果业实现数字化转型具有重要意义。该研究在数字植物技术范畴下,系统论述了数字果树的概念和内涵,提出了数字果树技术体系框架。重点在果树表型信息获取、环境数据获取、三维模型计算、数字育种、果树大数据和虚拟现实技术等方面综述了数字果树研究进展。从产业应用角度,综述了数字果树技术在树形管理、生长监测、种植管理、农技培训、品牌营销等方面应用效果和挑战。最后,展望了数字果树发展趋势、研究热点和技术突破方向,以期为数字果树的进一步发展提供思路与借鉴。