Winter Refuge Research Articles

Movement and Home Range of Nile Crocodiles in Ndumo Game Reserve, South Africa

The study of movement patterns and home range is fundamental in understanding the spatial requirements of animals and is important in generating information for the conservation and management of threatened species. Ndumo Game Reserve, in north-eastern KwaZulu-Natal, bordering Mozambique, has the third largest Nile crocodile (Crocodylus niloticus) population in South Africa. Movement patterns of 50 Nile crocodiles with a total length of between 202 cm and 472 cm were followed over a period of 18 months, using mark-resight, radio and satellite telemetry. The duration of radio transmitter attachment (131 ± 11.4 days) was significantly and negatively related to total length and reproductive status. Satellite transmitters failed after an average of 15 ± 12.5 days. Home range was calculated for individuals with 10 or more radio locations, spanning a period of at least 6 months. There was a significant relationship between home range size and total length, with sub-adults (1.5 m – 2.5 m) occupying smaller, more localised home ranges than adults (> 2.5 m). The largest home ranges were for adults (> 2.5 m). Home ranges overlapped extensively, suggesting that territoriality, if present, does not result in spatially discrete home ranges of Nile crocodiles in Ndumo Game Reserve during the dry season. Larger crocodiles moved farther and more frequently than smaller crocodiles. The reserve acts as a winter refuge and spring breeding site for an estimated 846 crocodiles, which also inhabit the Rio Maputo during the summer months. Nile crocodile movement out of the reserve and into the Rio Maputo starts in November and crocodiles return to the reserve as water levels in the floodplain recede in May.Conservation implications: Movement patterns of Nile crocodiles show the important role the reserve plays in the conservation of Nile crocodile populations within the greater Ndumo Game Reserve–Rio Maputo area.

Spatial segregation, dispersion and migration in early stages of polar cod Boreogadus saida revealed by otolith chemistry

Arctic marine food webs are centered on polar cod (Boreogadus saida), a small, largely pelagic gadid, which movement and migration remain unclear, especially for the early life stages. The present study examined the otolith chemistry of juvenile polar cod from six oceanographic regions of the Arctic Ocean in order to document patterns of spatial segregation, dispersion and migration during the species early life. The freshwater winter refuge hypothesis, suggesting that polar cod larvae start to hatch in winter in freshwater-influenced regions but only later in the season in purely marine regions, was also tested. Five elemental ratios (Li/Ca, Mg/Ca, Mn/Ca, Sr/Ca and Ba/Ca) were analyzed by laser ablation inductively coupled plasma mass spectrometry in three otolith zones representing the egg, larval and juvenile stages. The concentration of each of the five elements at the edge of the otoliths, corresponding to incorporation shortly before capture, was significantly correlated with surface salinity and temperature at capture site and date. Otolith chemistry differed between juveniles from freshwater-influenced regions (Laptev Sea, Hudson Bay Amundsen Gulf) and those from purely marine regions (Lancaster Sound, Baffin Bay, Frobisher Bay), in agreement with dissolved concentrations of at least some of the target elements in the Arctic Ocean. Discriminant function analyses including all five elements provided valuable information on the species population structure and dispersion of early stages. The correspondence between otolith Mn/Ca, Ba/Ca and vertical profiles of dissolved Mn and Ba in the water column may reflect the ontogenetic vertical migration of juvenile polar cod in late-summer and fall.

Periodic Systems of Delay Differential Equations and Avian Influenza Dynamics

Modelling the spread of avian influenza by migratory birds between the winter refuge ground and the summer breeding site gives rise to a periodic system of delay differential equations exhibiting both the cooperative dynamics (transition between patches) and the predator-prey interaction (disease transmission within a patch). Such a system has two important basic reproductive ratios, each of which being the spectral radius of a monodromy operator associated with the linearized subsystem (at a certain trivial equilibrium): the (ecological) reproduction ratio R0c for the birds to survive in the competition between birth and natural death, and the (epidemiological) reproduction ratio R0p for the disease to persist. We calculate these two ratios by our recently developed finite-dimensional reduction and asymptotic techniques, and we show how these two ratios characterize the nonlinear dynamics of the full system.

Winter refuge for Aedes aegypti and Ae. albopictus mosquitoes in Hanoi during Winter.

Dengue occurs throughout the year in Hanoi, Vietnam, despite winter low temperatures <10°C. During July 2010 to March 2012, we surveyed monthly for Aedes larvae and pupae in 120 houses in 8 Hanoi districts. Aedes albopictus preferred discarded containers in summer and pupal density drastically decreased in winter. Aedes aegypti preferred concrete tanks and this preference increased in winter. Even in winter, the lowest water temperature found in concrete tanks was >14°C, exceeding the developmental zero point of Ae. aegypti. Although jars, drums and concrete tanks were the dominant containers previously (1994–97) in Hanoi, currently the percentage of residences with concrete tanks was still high while jars and drums were quite low. Our study showed that concrete tanks with broken lids allowing mosquitoes access were important winter refuge for Ae. aegypti. We also indicate a concern about concrete tanks serving as foci for Ae. aegypti to expand their distribution in cooler regions.

Seasonal migration dynamics: periodicity, transition delay and finite-dimensional reduction

We study a model of bird migration between the summer breeding ground and the winter refuge site. The model involves time lags for the transition time between the patches, and the model parameters are periodic in time as the biological activities related to the migration and reproduction are seasonal. It has been shown in previous studies that the model system exhibits threshold dynamics: either all solutions converge to the trivial solution, or the system has a positive and globally attractive periodic solution. Two issues remain and will be addressed in this paper: how to express the threshold condition in terms of model parameters explicitly (rather than the abstract spectral radius of a certain monodromy operator) and how to describe the temporal pattern of the positive periodic solution. We make an interesting and surprising observation that the delay differential system is completely characterized by a finite-dimensional ordinary differential system and then a finite-dimensional map in the sense that the bird population at the initial time of spring migration determines the future status of the system. As a consequence, we derive the threshold condition, explicitly in terms of the model parameters, for the extinction and persistence of the considered bird species.

Caves as a Winter Refuge by a Neotropical Harvestman (Arachnida, Opiliones)

Caves as a Winter Refuge by a Neotropical Harvestman (Arachnida, Opiliones)

Spatially explicit modeling of conflict zones between wildlife and snow sports: prioritizing areas for winter refuges

Outdoor winter recreation exerts an increasing pressure upon mountain ecosystems, with unpredictable, free-ranging activities (e.g., ski mountaineering, snowboarding, and snowshoeing) representing a major source of stress for wildlife. Mitigating anthropogenic disturbance requires the spatially explicit prediction of the interference between the activities of humans and wildlife. We applied spatial modeling to localize conflict zones between wintering Black Grouse (Tetrao tetrix), a declining species of Alpine timberline ecosystems, and two free-ranging winter sports (off-piste skiing [including snow-boarding] and snowshoeing). Track data (snow-sports and birds' traces) obtained from aerial photographs taken over a 585-km transect running along the timberline, implemented within a maximum entropy model, were used to predict the occurrence of snow sports and Black Grouse as a function of landscape characteristics. By modeling Black Grouse presence in the theoretical absence of free-ranging activities and ski infrastructure, we first estimated the amount of habitat reduction caused by these two factors. The models were then extrapolated to the altitudinal range occupied by Black Grouse, while the spatial extent and intensity of potential conflict were assessed by calculating the probability of human-wildlife co-occurrence. The two snow-sports showed different distribution patterns. Skiers' occurrence was mainly determined by ski-lift presence and a smooth terrain, while snowshoers' occurrence was linked to hiking or skiing routes and moderate slopes. Wintering Black Grouse avoided ski lifts and areas frequented by free-ranging snow sports. According to the models, Black Grouse have faced a substantial reduction of suitable wintering habitat along the timberline transect: 12% due to ski infrastructure and another 16% when adding free-ranging activities. Extrapolating the models over the whole study area results in an overall habitat loss due to ski infrastructure of 10%, while there was a > 10% probability of human-wildlife encounters on 67% of the remaining area of suitable wintering habitat. Only 23% of the wintering habitat was thus free of anthropogenic disturbance. By identifying zones of potential conflict, while rating its relative intensity, our model provides a powerful tool to delineate and prioritize areas where wildlife winter refuges and visitor steering measures should be implemented.

New aerial survey and hierarchical model to estimate manatee abundance

AbstractMonitoring the response of endangered and protected species to hydrological restoration is a major component of the adaptive management framework of the Comprehensive Everglades Restoration Plan. The endangered Florida manatee (Trichechus manatus latirostris) lives at the marine‐freshwater interface in southwest Florida and is likely to be affected by hydrologic restoration. To provide managers with prerestoration information on distribution and abundance for postrestoration comparison, we developed and implemented a new aerial survey design and hierarchical statistical model to estimate and map abundance of manatees as a function of patch‐specific habitat characteristics, indicative of manatee requirements for offshore forage (seagrass), inland fresh drinking water, and warm‐water winter refuge. We estimated the number of groups of manatees from dual‐observer counts and estimated the number of individuals within groups by removal sampling. Our model is unique in that we jointly analyzed group and individual counts using assumptions that allow probabilities of group detection to depend on group size. Ours is the first analysis of manatee aerial surveys to model spatial and temporal abundance of manatees in association with habitat type while accounting for imperfect detection. We conducted the study in the Ten Thousand Islands area of southwestern Florida, USA, which was expected to be affected by the Picayune Strand Restoration Project to restore hydrology altered for a failed real‐estate development. We conducted 11 surveys in 2006, spanning the cold, dry season and warm, wet season. To examine short‐term and seasonal changes in distribution we flew paired surveys 1–2 days apart within a given month during the year. Manatees were sparsely distributed across the landscape in small groups. Probability of detection of a group increased with group size; the magnitude of the relationship between group size and detection probability varied among surveys. Probability of detection of individual manatees within a group also differed among surveys, ranging from a low of 0.27 on 11 January to a high of 0.73 on 8 August. During winter surveys, abundance was always higher inland at Port of the Islands (POI), a manatee warm‐water aggregation site, than in the other habitat types. During warm‐season surveys, highest abundances were estimated in offshore habitat where manatees forage on seagrass. Manatees continued to use POI in summer, but in lower numbers than in winter, possibly to drink freshwater. Abundance in other inland systems and inshore bays was low compared to POI in winter and summer, possibly because of low availability of freshwater. During cold weather, maps of patch abundance of paired surveys showed daily changes in manatee distribution associated with rapid changes in air and water temperature as manatees sought warm water with falling temperatures and seagrass areas with increasing temperatures. Within a habitat type, some patches had higher manatee abundance suggesting differences in quality, possibly due to freshwater flow. If hydrological restoration alters the location of quality habitat, postrestoration comparisons using our methods will document how manatees adjust to new resources, providing managers with information on spatial needs for further monitoring or management. Total abundance for the entire area was similar among survey dates. Credible intervals however were large on a few surveys, and may limit our ability to statistically detect trends in total abundance. Additional modeling of abundance with time‐ and patch‐specific covariates of salinity, water temperature, and seagrass abundance will directly link manatee abundance with physical and biological changes due to restoration and should decrease uncertainty of estimates. © 2011 The Wildlife Society.

Preserving frugivorous birds in agro‐ecosystems: lessons from Spanish olive orchards

Summary1. Frugivorous birds are a priority for conservation. They are experiencing the transformation of natural habitats to agro‐ecosystems worldwide and some are taking advantage of agricultural production of fleshy‐fruited plants. However, the mechanisms through which some birds are able to thrive in agricultural landscapes while others become extinct are poorly known.2. This manuscript provides an overview of avian frugivory in olive orchards, one of the principal agro‐ecosystems in the Mediterranean region and an important winter refuge for birds. The hypothesis that Mediterranean avian frugivores are pre‐adapted to olive orchards is used to consider potential constraints to bird occupation of wider agro‐ecosystems.3. Agricultural practices and artificial selection of fruit cause habitat and landscape simplification and reduction of bird food resources in orchards, with resulting negative effects on bird diet and body condition, as well as on bird abundance and diversity. Some of these constraints can be partially overcome by the presence of small hedgerows and copses in the agricultural landscape.4. Five pre‐adaptive features determine the successful occurrence of a bird species in olive orchards: (1) frugivorism intensity; (2) ability to track variation in fruit availability; (3) diet plasticity to cope with low fruit diversity and unbalanced food; (4) fruit handling plasticity to cope with oversized fruits; and (5) ecomorphology and foraging niche conditions which increase the ability to respond to habitat simplification.5. Synthesis and applications. Management practices have the potential to alleviate the constraints that habitat simplification puts on bird movement and diet. Two inter‐related approaches to management are proposed: increasing landscape and habitat diversity by the occurrence of hedgerows and forest remnants; and increasing food availability through reducing the use of pesticides and promoting fruit diversity in hedges.

A seasonal shift in habitat suitability enhances an annual predator subsidy

1. Entry of substantial numbers of natural enemies from outside a habitat can have profound impacts on food web structure in the recipient habitat, but underlying mechanisms are poorly understood, including the role of relative predator fitness in source and recipient habitats. We studied a naturally occurring annual movement of the salt-marsh spider Pardosa littoralis across habitats in an attempt to clarify factors enhancing and impeding movements of predator populations. 2. Marsh vegetation is dominated by two cordgrass species, Spartina patens, a complex-structured grass with a well-developed litter layer, and Spartina alterniflora, a sparse-structured grass with little thatch accumulation. Pardosa hunts across both habitats and can drastically reduce densities of planthoppers and leafhoppers, the most abundant marsh herbivores. 3. We found an annual subsidy of Pardosa from S. patens, extending hundreds of meters into S. alterniflora made possible by a winter refuge provided by S. patens. As a result, the strength of the subsidy is correlated with the severity of the preceding winter, with the largest subsidies following the coldest winters. 4. Higher Pardosa fitness in the recipient habitat following winter, as indicated by higher growth rates associated with greater prey availability, enhanced the strength of this subsidy. Conversely, lower structural complexity in S. alterniflora, which is associated with higher rates of cannibalism in this spider, may impede the subsidy. 5. The mechanistic underpinnings of the predator subsidy demonstrated here can improve our understanding of subsidies in other contexts, such as conservation biological control. In addition, identifying such subsidies is key to preserving food webs in recipient habitats when source habitats are threatened.

“Sleeping with the enemy”—predator-induced diapause in a mite

Diapause in arthropods is a physiological state of dormancy that is generally thought to promote survival during harsh seasons and dispersal, but it may also serve to avoid predation in space and time. Here, we show that predation-related odours induce diapause in female adult spider mites. We argue that this response allows them to move into an area where they are free of enemies, yet forced to survive without food. Spider mites are specialised leaf feeders, but--in late summer--they experience severe predation on leaves. Hence, they face a dilemma: to stay on the leaf and risk being eaten or to move away from the leaf and risk death from starvation and thirst. Female two-spotted spider mites solve this dilemma by dramatically changing their physiology when exposed to predation-associated cues. This allows them to disperse away from leaves and to survive in winter refuges in the bark of trees or in the soil. We conclude that the mere presence of predation-associated cues causes some herbivorous mites to seek refuge, thereby retarding the growth rate of the population as a whole: a trait-mediated indirect effect that may have consequences for the stability of predator-prey systems and for ecosystem structure.

Olfactory recognition of terrestrial shelters in female Northern Spectacled Salamanders Salamandrina perspicillata (Caudata, Salamandridae)

Olfactory recognition of terrestrial shelters in female Northern Spectacled Salamanders Salamandrina perspicillata (Caudata, Salamandridae). Chemical cues are used as ubiquitous markers of individual, group, kinship, and species identity. Northern Spectacled Salamander (Salamandrina perspicillata) is a semi-terrestrial and elusive species. Females can be found in water bodies just in the spawning season but spend most of their life, as well as males do, in terrestrial shelters such as cracks, crevices and under stones to reduce the risks of dehydration. We have investigated whether, in reproductive females, animal's own and conspecific chemical cues play a role in the shelter choice. We performed unforced two-choice system tests in order to study the behavioural response of salamanders to scent marks. For each test, the choice between two artificial shelters (plastic tubes) was offered to each focal indi- vidual. Data were analyzed using the binomial distribution. Our results show that Salamandrina use the sense of smell in the terrestrial shelter choice as animals (i) were capable to discriminate between a tube previously used by itself and a unused one (P 0.05). We suggest that attraction towards conspecific smells could favour a gregarious behaviour in winter refuges.

Effects of artificial woody structures on Atlantic salmon habitat and populations in a Nova Scotia stream

AbstractA 1‐km reach of Brierly Brook, Nova Scotia, was studied from 1995 to 2004 to determine if the addition of artificial structures mimicking large woody debris could enhance Atlantic salmon populations. In 1995, digger logs (which mimic fallen trees) and deflectors (which narrow the channel) were constructed in a 250‐m section of the brook devoid of woody debris (Old Restored Site). In 2003, 5 more digger logs and defectors were built in a previously unrestored section of the stream (New Restored Site). A third control site was left unchanged. Physical changes caused by the structures were monitored at the New Restored Site. Densities of juvenile and spawning Atlantic salmon were also monitored. At all sites, woody debris structures in the brook were important and effective in creating complex salmonid habitat. The structures narrowed the channel, scoured pools and undercut banks. They created habitat that parr used for summer and winter refuge and adult spawners used for cover and resting during upstream migration and spawning. The structures caused gravels to accumulate that spawning adults used to build redds and fry used for shelter. The reaches with structures had higher spawning densities than reaches without them; spawning increased in the New Restored Site relative to the control site. The absence of woody debris may be a bottleneck for salmonid populations in streams of the Atlantic Northeast. For streams with a small or immature riparian zone and little woody debris in the channel, woody structures may be an effective tool for restoring salmonid populations. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Effect of heterospecifics on foraging of endangered red‐crowned and white‐naped cranes in the Korean Demilitarized Zone

AbstractWe determined how the presence of heterospecific individuals in the vicinity of a focal individual affects the behavior of two critically endangered species of cranes on their wintering grounds at Cheolwon in the Korean Demilitarized Zone. The red‐crowned crane, Grus japonensis, is larger than the white‐naped crane, Grus vipio, and it dominates the white‐naped crane in aggressive interactions. We showed that the dominant species increases foraging activity in the presence of the subordinate species presumably because of scrounging of food from the subordinate. Because interspecific interactions may affect avian endangerments these behavioral findings should be taken into account when managing winter refuges for the two endangered crane species.

IMPACT OF SPECIAL EARLY HARVEST SEASONS ON SUBARCTIC-NESTING AND TEMPERATE-NESTING CANADA GEESE

Dramatic changes in wintering distributions of Canada geese (Branta canadensis) have occurred over the past 50 years in eastern North America. Declines in numbers of subarctic-nesting geese wintering in southern states, and increases in numbers wintering in northern regions, have resulted in a northern shift in winter distributions. In contrast, numbers of temperate-nesting geese have increased throughout eastern North America. Management efforts to control overabundant temperate-nesting flocks have included the establishment of special early harvest seasons in September. However, the effect of early seasons on survival and harvest of subarctic-nesting populations has not been documented. Understanding the timing of migration movements and the fidelity of subarctic-nesting flocks to terminal winter refuges in the Southeast also is necessary to design early harvest seasons that target temperate-nesting flocks and protect subarctic-nesting populations. We used recoveries of marked geese to estimate survival and harvest rates before and after implementation of early harvest seasons within the Mississippi Flyway during 1976–1999. In addition, we used observations of neck-banded geese from the Southern James Bay Population (SJBP) to evaluate the hypothesis that subarctic-nesting geese arriving prior to mid-December on several key terminal winter refuges in the Southeast (early arriving migrants) were more likely to return to those refuges in subsequent years than were migrants arriving after mid-December (late arriving migrants). September seasons during 1987–1994 were a minor source of mortality for subarctic-nesting populations and accounted for <10% of their annual harvest mortality. The effectiveness of early seasons for increasing mortality of temperate-nesting flocks varied among the states we examined and was tempered by concurrent changes in state-specific harvest regulations during the regular harvest season. For SJBP Canada geese, annual fidelity to southeastern refuges was 10% higher for early arrivers than for late arriving geese. However, in any given year only 47–57% of the surviving geese were expected to return to the refuges the following year. Although early arriving migrants had higher survival and higher return probabilities than did late arriving migrants or geese that failed to return, numbers of geese wintering on southeastern refuges likely declined because <60% of the surviving geese affiliated with the refuges would return in a given year and because of lower survival for geese that did not return to the refuges.

Yellowstone to Yukon (Y2Y) – einer der größten internationalen Wildtierkorridore

On the North American continent, many wildlife species have persisted that have disappeared or are highly endangered in Europe. Observations of extensive wolf (Canis lupus) migrations along the Rocky Mountains led to the establishment of the Yellowstone to Yukon (Y2Y) conservation project in 1997. The project is aimed at preserving biodiversity by creating one of the world's largest wildlife corridors ranging from the Yellowstone National Park in the northwestern part of the USA to the Yukon Territory in northern Canada. More than 270 organisations, First Nations, and governmental institutions are involved in the project. Research on urban regeneration shall identify areas for wildlife corridors, winter refuges, or rest areas. Some 200 large areas with high protection status in the Rocky Mountains need to be complemented by additional buffer zones, wildlife areas and national parks in the near future. The Y2Y corridor is intended to be linked to a comprehensive wildlife corridor system connecting the southern USA with Central and South America. On the North American continent, many wildlife species have persisted that have disappeared or are highly endangered in Europe. Observations of extensive wolf (Canis lupus) migrations along the Rocky Mountains led to the establishment of the Yellowstone to Yukon (Y2Y) conservation project in 1997. The project is aimed at preserving biodiversity by creating one of the world's largest wildlife corridors ranging from the Yellowstone National Park in the northwestern part of the USA to the Yukon Territory in northern Canada. More than 270 organisations, First Nations, and governmental institutions are involved in the project. Research on urban regeneration shall identify areas for wildlife corridors, winter refuges, or rest areas. Some 200 large areas with high protection status in the Rocky Mountains need to be complemented by additional buffer zones, wildlife areas and national parks in the near future. The Y2Y corridor is intended to be linked to a comprehensive wildlife corridor system connecting the southern USA with Central and South America.

Will climate change depose monarchs: Model predicts too‐wet winter refuges

Science NewsVolume 164, Issue 20 p. 310-310 This Week Will climate change depose monarchs: Model predicts too-wet winter refuges Susan Milius, Susan MiliusSearch for more papers by this author Susan Milius, Susan MiliusSearch for more papers by this author First published: 02 July 2009 https://doi.org/10.2307/4018901AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume164, Issue2015 November 2003Pages 310-310 RelatedInformation

The cost of aggregation: juvenile salmon avoid sharing winter refuges with siblings

Kin selection advantages are usually accrued by individuals that associate with close relatives. But aggregation may also be costly, by increasing the risk of predation or resource competition, for example. As a result, individuals should increase their inclusive fitness by trading the costs and benefits of kin association and aggregation. Studies of kin selection to date have focused on situations where there is ample opportunity for kin-biased behavior and therefore for the formation of kin groups. Here we used juvenile Atlantic salmon to test an alternative strategy: that under conditions where the potential for kin-biased behavior is negligible, individuals should, when aggregating, avoid rather than associate with kin to avoid imposing the costs of aggregation upon close relatives. By testing salmon during winter, when juveniles shelter inactively in streambed refuges, we tested whether individuals associate with or avoid their siblings at a time when the opportunity for kin-directed behaviors is restricted. Our results provide the first evidence of kin avoidance in nonreproductive animals studied under semi-natural conditions. Copyright 2003.

Towards the on‐farm conservation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) during winter using crop plants as refuges

Abstract Habitat instability associated with seasonal crop succession in broad‐acre farming systems presents a problem for the conservation and utilisation of beneficial insects in annual field crops. The present paper describes two experiments used to measure the potential of seven plant species to be utilised as winter refuges to support and conserve the predatory bug Pristhesancus plagipennis (Walker). In the first experiment, replicated plots of canola (Brassica napus), red salvia (Salvia coccinea), niger (Guizotia abyssinica), linseed (Linum usitatissimum), lupins (Lupinus angustifolius), and lucerne (Medicago falcata) were planted in a randomized experiment during Autumn 1998. Upon crop establishment, adults and nymphs of P. plagipennis were released into treatment plots and their numbers were assessed, along with those of their potential prey, throughout the ensuing winter months. Post‐release sampling suggested that canola and niger retained a proportion of adult P. plagipennis, while niger, lucerne and canola retained some nymphs. The other plant species failed to support P. plagipennis nymphs and adults postrelease. In the second experiment, niger was compared with two lines of sunflower (Helianthus annus). Both sunflower lines harboured significantly higher (P &lt; 0.05) densities of P. plagipennis nymphs than did niger. The more successful refuge treatments (sunflower, niger and canola) had an abundance of yellow flowers that were attractive to pollinating insects, which served as supplementary prey on which P. plagipennis were observed to feed. Sunflower and niger also supported high densities of the prey insect Creontiades dilutus (Stål) and provided protective leafy canopies which supplied shelter during the winter months. The potential and limitations for using each plant species as a winter refuge to retain P. plagipennis during winter are discussed.

1998-1999 Detection Survey Results of Diabrotica virgifera virgifera LeConte in Non-infested European Countries

Thysanoptera species were collected from Stellaria media in autumn, winter and spring in different biotopes, in Hungary. The total number of the sampled specimens was 5121. The most frequent species were (in order of frequency): Thrips tabaci, T. atratus, Frankliniella intonsa, Apti­no­­thrips rufus, T. minutissimus, T. nigropilosus and Anaphothrips ob­scu­rus. The number of species as well as the composition of the species occurr­ing on S. media depends on the characteristics of biotopes. The number of species considerably increased in spring from 15 to 43. Among them seven species occurred from autumn through winter till spring. S. media provides a suitable site for winter refuge, and an alternative food source for a few species, which hibernate under bark, fallen leaves and dry grass as well as in the soil, leaving their winter quarters move and accu­mulate temporarily on this plant. Specimens of T. tabaci capable of harbouring tomato spotted wilt virus occurred in every investigated biotopes.