Managed honey bee colonies face severe winter losses in northern climates. In my studies, interactions between genotypes of bees (genetically selected stock and unselected stock) with different levels of resistance and tolerance to varroa mites were assessed under a variety of treatment combinations to quantify effects of queen pheromone, acaricide treatment, wintering method, ventilation condition and pathogen infection on the costs and benefits associated with mite removal and mite-tolerance behaviors. In most of the experiments, mite-resistance caused greater varroa mite mortality within selected stock relative to unselected stock. Artificial and natural sources of queen pheromone caused greater varroa mite mortality within honey bee colonies relative to queenless colonies. While mite resistance had significant benefits, I showed that when producers selected colonies containing some mite resistance traits, it was traits associated with mite-tolerance and not mite-resistance were maintained and contributed to wintering success. Tolerance was effective at two levels of mites as obtained by late autumn treatment of colonies with oxalic but treatment did not improve wintering performance of either stock. Selected stock showed greater colony size, survival and resulted in more viable colonies in spring in comparison to unselected stock with similar initial mite levels (0.16 mites per bee). Selected stock showed greater relative wintering success than unselected stock when wintered indoors than when wintered outdoors but indoor wintering improved colony survival in both stocks relative to outdoor wintering. Carbon dioxide level increased within the winter bee cluster when colonies were maintained under restricted-ventilation (mean 3.82±0.031%, range 0.43-8.44%) and restricted ventilation increased mite mortality by 138% relative to standard-ventilation (mean 1.29±0.031%, range 0.09-5.26%), but restricted-ventilation did not affect bee mortality in comparison to standard-ventilation. In a laboratory study, I showed that Nosema inoculation (with co-infections of N. ceranae and N. apis) suppressed the effectiveness of mite removal behavior within selected bees relative to unselected bees. N. ceranae was more abundant than N. apis. Bees with greater mite removal capacities had higher costs associated with varroa-resistance as indicated by greater bee mortality rates when inoculated with varroa but bee mortality was not affected in Nosema inoculated bees.

Bactrocera tryoni, the Queensland fruit fly, is established along the entire Australian east coast. It is a major pest of horticulture and arguably the worst horticultural insect pest in Australia. Adult flies lay eggs into fruit and resultant larvae feed on the flesh of the fruit. The population biology of B. tryoni has been well studied in temperate regions, where it has been established that climatic factors, particularly temperature and rainfall, limit population growth. In contrast, in subtropical and tropical regions, the population dynamics of the fly have been little studied. This thesis investigates the fly's phenology and abundance changes across subtropical and tropical Queensland and asks what factors govern the population cycles of B. tryoni in this state. Winter breeding and abundance of the fly, a component of the seasonal cycle which in south-east Queensland is fundamentally different from that observed in temperate Australia, is also investigated. A historical, extensive multi-year and multi-site trapping data set with from across Queensland was analysed to look at the effects of temperature, rainfall and relative humidity on B. tryoni trap catch. Trap data was further compared with the predicted phenology data generated by a DYMEX® based B. tryoni population phenology model. The phenology model used was based on a previously published model, but was also modified to more explicitly look at the effects of host plant availability and the presence or absence of non-reproductive over-wintering flies. Over-wintering field cage studies and a winter-spring field trapping study, both carried out in Brisbane, supplied additional data on B. tryoni's population abundance and capacity to breed during winter in the subtropics. Results show significant variation of monthly fly abundance for nine sites across Queensland. Abundance changed across sites in non-predictable ways. Annual population phenology within a site was, for some sites, highly consistent from year to year, but inconsistent for other sites. All sites in the subtropics showed some form of population depression during the cooler months, but breeding was continuous, albeit reduced at nearly all sites. Some tropical sites, where the climate is regarded as highly favourable for B. tryoni, still showed dramatic peaks and troughs in annual population abundance. There were relatively few significant correlations observed between weather factors and fly populations for any site. Output from the DYMEX population model suggested that fruit availability is a major driver of population dynamics in the tropical north of the state, while weather is more important in the subtropical south. The population dynamics of B. tryoni at sites along the central Queensland coast, where it is assumed that a mix of both weather and host fruit availability drive local populations, were poorly captured by the population model. Field cage results showed that B. tryoni successfully bred during winter in Brisbane, with pupal emergence starting in mid-winter (1st week of August), peaking in early spring (2nd week of September). Trap catch at orchards in Brisbane increased with increasing temperature and fruit availability, but diminished with decreasing temperature and fruit availability. The results suggest that B. tryoni has an optimal climate for population growth in the tropics, but fruit availability for offspring production limits population growth. In the subtropics however, both climate and fruit availability determine the population size. Winter temperatures are marginal for B. tryoni population growth in the subtropics.

No description available.

Wetlands have been considered an important component of wintering moose (Alces alces andersonii) habitat in the West-Chilcotin Region of British Columbia. This study evaluates the importance of wetlands, particularly the ecotone between forests and wetlands and identifies important cover types for wintering moose. Additional baseline data regarding food habits and home range sizes are included. Two hypotheses were tested in this study; that moose habitat use was independent of cover type, and that moose habitat use was random with respect to distance from forest/wetland borders. The data in this study led to rejection of both these hypotheses. Moose used spruce (Picea glauca) wetlands and spruce forests more frequently than expected if use were random. Moose concentrated primarily within 100 m of the forest/wetland edge and virtually did not use areas greater than 200 m from the edge. The combination of food and cover in areas of spruce and edge is likely a major factor determining habitat use of wintering moose. Average home range sizes of radio-collared moose ranged from 20.7 to 45.2 km². Bog birch (Betula qlandulosa) , lodgepole pine (Pinus contorta), and willows (Salix spp.) were the most frequently consumed forages. / Land and Food Systems, Faculty of / Graduate

Segregation, that animals of different sex and/or age do not spend time together all year round, is a common phenomenon. One example is that males and older individuals in migratory birds wintering further north. Migration time also affects the distribution of birds in the wintering area. European Robins that migrate in late autumn tend to winter farther east. Another factor that affects wintering areas is global warming. Today wintering birds do not migrate as far as they used to. The aim was therefore to investigate if Robins segregate during winter and if they segregate by sex, age and/or migration time and to see if the wintering area has changed since 1950. Analysis of Robins ringed at Ottenby Bird Observatory that has been recovered during winter was conducted. To obtain an indication on what influences Robins in their choice of wintering area, an analysis was done with migration year, age, and migration time (sex was excluded in this analysis) to analyse what effects migration distance. The geographical centroid was used for representing the wintering area. The difference between the group’s centroid was tested with a permutation test. The result indicated that migration time best explains the distribution of Robins in the wintering area. Robins that migrate late migrate shorter and winter further northeast, this is probably due to sequential migration of different populations. No effect of age or migration year was observed. The wintering area appears to have moved north, which indicates that Robins are affected by global warming.

Estimates of abundance are critical to manage and conserve waterfowl and their habitats. Most surveys of wintering waterfowl do not use probability sampling; therefore, development of more rigorous methods is needed. In response, I designed and evaluated an aerial transect survey to estimate abundance of wintering ducks in western Mississippi during winters 2002?2004. I designed a probability-based survey using stratified random and unequal probability sampling of fixed-width transects. To correct for visibility bias inherent in aerial surveys, I conducted an experiment to model bias and incorporated correction factors into estimation procedures to produce adjusted estimates. Bias-corrected estimates were most accurate. Precision of abundance estimates of total ducks met a priori goals (CV ≤ 15%) in 10 of 14 surveys. Based on a simulation study, the implemented survey design provided the most precise estimates, yet certain refinements remained possible. I also illustrated potential applications of survey results in the context of conservation and management of wintering waterfowl populations and habitats. I described patterns of abundance within and among winters, including a comparison with surveys conducted during winters 1988?1990 that revealed mallard abundance decreased 65% from the late 1980s. I developed a method to illustrate population abundance spatially for scientific and public education. I attempted to explain temporal variation in abundance estimates relative to variables potentially representing hypotheses explaining regional distributions of ducks. I concluded the data provided stronger support for factors related to energy conservation by ducks than factors related to energy acquisition. Finally, I determined associations between duck distributions and habitat and landscape features in accordance with the habitat-complex conceptual model. Landscapes with greater interspersion and diversity of wetlands attracted increased numbers of ducks, a though other factors such as wetland area also were important. I concluded that this study advanced methodologies to survey wintering waterfowl. Although improvements were warranted, I recommend this survey design for continued monitoring of wintering ducks in western Mississippi. Furthermore, I suggest habitat management on public and private lands should include complexes of seasonally flooded cropland, moist-soil, forested, and permanent wetlands to potentially increase wintering duck numbers in western Mississippi.

Master of Science

Blackburnian Warblers (Dendroica fusca) were observed in their wintering grounds in a High Andean native secondary forest in Colombia between September 1993 and May 1994. The main objective of the study was to determine the relationships between the Blackburnian Warblers and the habitats where they were found. Size and composition of the mixed-species flocks joined by Blackburnian Warblers were also compared to habitat features. Habitat variables were measured in circular plots centered where a Blackburnian Warbler was first seen. The same set of variables was measured in randomly located paired plots to compare the two sets. The results obtained in Colombia (wintering grounds) were compared to similar data available from North America (breeding grounds). Ninety-six mixed-species flocks with Blackburnian Warblers were detected. Some of the habitat variables measured differed between plots used by the birds and the random plots. Density of trees in all dbh (diameter at breast height) categories, density of snags and density of native trees and shrubs were higher at the bird-centered plots. Percentage vegetation density (understory foliage volume) from O-1m, 1-2m and 2-3m were lower at bird-centered plots. There was no significant difference for maximum and mean canopy height between bird-centered and randomly selected paired plots. At Los Amarillos, Blackburnian Warblers avoided Eucalyptus spp. trees. They preferred the higher part of the trees and trees in the middle and high abh classes. They avoided the smallest dbh size class (3-8cm dbh). Comparisons were made between the data from Los Amarillos and data available from northern central Minnesota (Collins et al. 1982). Percent ground cover, densities of trees 15.1-23, 23.1-38 and 38.1-53 cm dbh and total density of trees were significantly higher in Minnesota. Trees 7.5- 15, 53.1-68 and > 68.1 cm dbh were higher in Los Amarillos. Percent canopy cover was not different between the two Sites. Blackburnian Warblers selected for closed canopy cover (about 75%) and large trees in each individual site. They selected larger trees in Minnesota. This selection may be related to nesting requirements of the species. / Master of Science

from the summer dry season to the winter wet season. Such movement that connects summer and winter habitats may be particularly important for coho salmon, O. kisutch, because availability of overwintering habitat can limit freshwater survival for this species. Here, I describe basin-scale variability in the spatial pattern of fall movement for juvenile coho salmon between mainstem and tributary streams during the fall of 2002, 2003, 2004, and 2005. Juvenile coho salmon were tagged with a passive integrated transponder (PIT) and could be detected at five stationary detection sites, two located in perennial tributaries, two in intermittent tributaries, and one in the upper mainstem of the West Fork Smith River, Oregon. For each detection site, I compare the likelihood of detection during the fall by juvenile coho salmon from tagging locations over a multi-kilometer range of distances in each direction away from the tributary confluence. I developed logistic regression models with data from each detection site to estimate: 1) the relative likelihood of immigration into a tributary as compared to emigration out of the tributary, and 2) the relative likelihood of immigration into a tributary from the mainstem downstream of the tributary confluence as compared to immigration from the mainstem upstream of the confluence. For each pair of directions at each detection site, I also compare the change in the likelihood of detection with increasing distance for each direction. Overall, at the two upper-river detection sites, juvenile coho salmon were more likely to emigrate than to immigrate. At the remaining detection sites, juvenile coho salmon were no more likely to emigrate than immigrate. Of these detection sites, fish that immigrated into the mid-river perennial stream were more likely to come from the mainstem downstream of the confluence, whereas fish that immigrated into the two lower-river intermittent tributaries were more likely to come from the mainstem upstream of the confluence. Fall movement of juvenile coho salmon between tributary and mainstem habitat can occur over relatively long distances. This case study demonstrates variation among tributaries in the overall likelihood of emigration and immigration and in the source of immigrants from the mainstem, which may be related to spatial context that combines the physical characteristics and network position of tributary streams. The demonstrated variation in fall movement that connects summer and winter habitat within a stream network is a first step in exploring how complexity in movement interacts with the spatial arrangement and quality of seasonal habitats. More research on the causes of variation in the expression of fall movement will improve our understanding of how the spatial arrangement of habitat within a stream network influences the survival of juvenile coho salmon over the whole freshwater life cycle. / Graduation date: 2013

Lauko eksperimentai atlikti 2009 – 2010 m. Lietuvos žemės ūkio universiteto bandymų stotyje, kur dirvožemis yra karbonatingas sekliai glėjiškas išplautžemis (Calc(ar)i-Epihypogleyic Luvisol). Mūsų tyrimo tikslas buvo nustatyti žieminių rapsų sėjos laiko poveikį rudens skrotelės cheminei sudėčiai ir augalų peržiemojimui. Skirtingu laiku sėtų žieminių rapsų skrotelės cheminė sudėtis turėjo įtakos augalų žiemojimui – tarp šių požymių buvo nustatyti įvairaus stiprumo statistiškai patikimi priklausomumai. Linijinės ‘Sunday‘ veislės rapsų skrotelės cheminė sudėtis stipriau įtakojo peržiemojimo proc., palyginus su hibridine ‘Kronos‘ veisle. Geriau peržiemojo hibridinės veislės rapsai (ypač sėti vėliau) – 39,2–77,0 proc. augalų, negu linijinės veislės – 12,8–54,0 proc. Geriausia žieminiai rapsai peržiemojo sėti rugpjūčio 30 - rugsėjo 5. Jie lapuose sukaupė 15,23-18,14% sausųjų medžiagų, 4,61-5,69% bendrojo cukraus, N ir K santykis lapuose buvo 1,64-1,76. Viršūniniame pumpure – 18,01-19,68% sausųjų medžiagų, 6,00-8,49% bendrojo cukraus, N ir K santykis buvo 1,49-1,69 ir šaknyse – 17,46-18,37% sausųjų medžiagų, 7,71-10,30% bendrojo cukraus, N ir K santykis buvo 1,05-1,56. Hibridinės veislės rapsai, ypač sėjant juos vėliau, intensyviau ruošiasi žiemojimui. Rapsų peržiemojimas priklausė nuo skrotelės cheminės sudėties: sausųjų medžiagų ir bendrojo cukraus kiekio, bei nuo N ir K santykio. / The experiment carried out in the Experimental Station of Lithuanian University of Agriculture in 2009 – 2010. The soil is shallow calcareous Luvisols (Calc(ar)i-Epihypogleyic Luvisol). The aim of our investigation was to determine the effect of sowing time of winter oilseed rape on autumn rosette chemical composition and over-wintering. Chemical composition of rossete of winter rape sown at different time influenced crop over-wintering – significant correlation between this indicators was established. The stronger influence of the winter rape rosette composition on over-wintering was established in rape of linear cultivar ‘Sunday‘ than in rape of hybrid cultivar ‘Kronos‘.Winter rape of hybrid cultivar over-wintered better – 39, 2–77,0%, winter rape of linear cultivar – 12,8–54,0%. Winter rape sown on 30 August – 5 September best over-wintered. They acumulated 15,23–18,14% of dry matter, 4,61–5,69% of total sugar, N and K ratio was 1,64–1,76 in leaves, and in apical bud – 18,01–19,68% of dry matter, 6,00–8,49% of total sugar, N and K ratio was 1,49–1,69 and in roots – 17,46-18,37% of dry matter, 7,71-10,30% of total sugar, N and K ratio was 1,05-1,56. Winter rape of hybrid cultivar sown at later dates prepared for over-wintering more intensively. Winter rape of both cultivars sown at the latest date not over-wintered. Over-wintering depended winter rape rosette on the chemical composition: dry matter and total sugar content, and the N and K ratio.