Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). "November 2008." Includes bibliographical references (p. 167-182). Also available via the World Wide Web.

Many species of farmland birds have shown huge declines in numbers and range since the 1970s due to agricultural intensification, and these declines have been worst amongst granivorous species. Recent studies have suggested that low abundance of invertebrate chick food may have been important in driving the declines of a number of granivorous species, however causation has still only been proved for the Grey Partridge, whose decline has been attributed to low chick survival due to the indirect effects of herbicides reducing invertebrate abundance. We investigated invertebrate declines and how they may have affected farmland bird populations in a number of ways. There is little long-term data on abundance of farmland invertebrates. Thus we first looked at how representative data from a long-running suction trap was of invertebrate abundance on local farmland. Suction trap catches reflected abundance of aerial invertebrates on local farmland, and also to abundance of epigeal invertebrates in many cases, particularly abundances in predominant crop types. Secondly, we looked at spatial and temporal distribution of invertebrates on farmland in order to make recommendations about how to increase invertebrate availability to farmland bird populations. Field margins were by far the most invertebrate rich habitats sampled. Most differences in invertebrate abundance between different crop types were found early in the season, at this time spring barley and spring oilseed rape had very low abundances. Winter wheat had relatively high invertebrate abundance compared to spring barley at this time. Winter oilseed rape and set-aside had relatively high abundances of the crop types sampled. We investigated how low invertebrate abundance may have affected populations of granivorous passerines by looking for evidence of reproductive trade-offs in a population of Tree Sparrows, and by supplementary feeding experiments with Tree Sparrow and Yellowhammer chicks. There was no evidence for reproductive trade-offs within years, conversely an effect of individual quality was found. There was some evidence of reproductive trade-offs between years. Supplementary feeding increased the mass of Tree Sparrow first broods early in May but not later in May, and also of chicks with yearling parents, who had a lower provisioning rate. Chicks fledged early in May had a lower survival rate to the following year than chicks fledged later, supplementary feeding and parental age had no effect on chick survival. Supplementary feeding a parent's first brood had no effect on their later reproductive output that season, or on their survival to the next breeding season. Supplementary feeding Yellowhammer chicks early season increased their mass, but had no effect later in the season. This complies with results from a previous study of Yellowhammers in southern England, which showed that a higher proportion of chicks fledge late in the season. Further analysis of this data showed that this was because chicks were more likely to starve early in the season, and also that chick mass was lower early season, even when just looking at chicks which went on to fledge. Thus, it would appear that low invertebrate abundance was affecting the granivorous passerines looked at most in the early season, and through chick mass and survival. Measures to increase invertebrate abundance at this time would be beneficial to populations of granivorous passerines.

Thesis (Ph.D.)--University of Western Australia, 2007.

Call number: LD2668 .T4 1984 S58 / Master of Science

This study examined modifications made by Pogonomyrmex barbatus, by their processes of granivory and nest construction, to forb and grass dynamics under large-scale disturbances of fire, recent drought and long-term, large-mammalian herbivory using comparative studies, field experimental manipulations, and a simulation model on the Edwards Plateau, Texas. Ant nests are refugia for grass survival during extreme droughts as demonstrated during the drought of 1998 to 2002. Significantly greater cover of grasses and lower abundance and cover of forbs was found beside nests compared with surrounding habitat throughout the drought and recovery. Grasses near nests may be the seed source for surrounding habitats during recovery. Seeds were differentially collected among most forbs and grasses despite seed abundance. Harvest was significantly reduced in the fall relative to spring. During preference experiments, harvest differences were found between grazing treatments for two of four species, but only during the spring. High lipid content seeds were unpreferred in fall compared to high protein and carbohydrate content seeds. Granivory influences on seedling establishment were studied by comparing seedling recruitment among sown and naturally occurring seeds excluded and open to foragers. Exclosures were placed in three nest densities and two burn treatments. Seeds in exclosures produced significantly more seedlings than open arenas only during the first year of drought recovery. Densities of grasses and annual forbs were higher in open arenas the second year due to indirect effects of granivory. By reducing seeds ants release seedlings from competition. Sown seedling abundance was unaffected by colony density and fire. Colony density and distribution were influenced by topography, soil types, soil depth and woody cover, but not by historical grazing treatments. Cleared vegetation on nest disks impacted less than 1% of total surface area and losses were compensated by greater basal cover of grasses next to disks compared to surrounding habitats. Foraging areas influenced 17.3-73.6% of surface area and could diminish seed populations for potential seedlings. Model results agree with experimental observations that communities may be modified by P. barbatus presence due to differential responses of grass species to interaction between nests or granivory and rainfall amounts.

Red-billed Quelea Quelea quelea have expanded their range in the Eastern Cape and now occur throughout the year in new areas. Recent changes in agricultural practice have probably been a contributing factor as flocks are larger than previously recorded and were more often associated with artificial food sources than natural grasses. Ringing and census data indicate that quelea have reduced movements during the non-breeding season and may display strong fidelity (over successive years) to dry season quarters with reliable food supplies. Although the recapture/recovery rate for quelea in the Eastern Cape (1.0-2.5%) was higher than the national average, it was still lower than expected and there may be considerable movement between nearby feeding sites. Some quelea breed locally, but most disperse during summer and their numbers at the feedlots were generally highest in winter and spring. The breeding season of quelea is later than other ploceids in the region and post-nuptial moult overlaps with winter. Replacement of primary wing feathers is relatively slow (124 days), and this is considered an adaptation to minimise disruption of flight capabilities and insulation. Significantly more quelea in the Eastern Cape have breeding plumage suffused with pink than in other southern African populations. However, during the non-breeding season there is apparently considerable intermixing between local populations and those from further north and the existence of a local sub-species is not supported. Seeds of two grass species, Echinochloa sp. and Urochloa panicoides, and two weed species, Amaranthus sp. and Chenopodium sp., were important in the diet of both quelea and Laughing Doves Streptopelia senegalensis. Maize comprised a large proportion of the diet of these species and losses at one ostrich feedlot were estimated at over R 17 000 in two years. Dependence on artificial food sources was generally greatest in winter and spring, but economically significant damage was not confined to this period. Alpha-chloralose showed good potential for reducing numbers of problem birds at livestock feedlots. However, the dynamic nature of problem bird populations favours a non-lethal management approach. Reduction of feed loss through manipulation of the ostrich ration could provide a relatively cheap and effective alternative to lethal control if applied appropriately.

[Truncated abstract] In the crop growing areas of Western Australia, two economically important weed species, Lolium rigidum Gaud. (annual ryegrass) and Raphanus raphanistrum L. (wild radish), have evolved widespread herbicide resistance to multiple chemistry groups. Consequently, grain growers in the region have adopted an integrated approach to weed management that includes many non herbicide tools, however many more are needed as these weed species become increasingly more difficult to control. This thesis examines, in a series of field trials carried out in the Western Australian crop growing area, the potential for weed seed predation of annual ryegrass and wild radish by naturally occurring granivores as a new weed management tool for grain growers . . . The study discusses the implications of these results with the view to manipulating predation of weed seed through agricultural management practices. Ants were shown to be the dominant seed predator in this environment, especially in the centre of fields. The study has identified that the ant species Melophorus turneri (Forel), Monomorium rothsteini (Forel), Pheidole hartmeyeri (Forel) and Rhytidoponera metallica (Smith) are potential biological control agents for annual ryegrass seeds while P. hartmeyeri was identified as the only species suitable for biological control of wild radish seed pods. Ants were found to be sensitive to disturbance and some to crop residue type and these effects are discussed in relation to seed removal. This study of weed seed predation in agricultural fields is the most complete in this environment and can be used to inform further work in this area. It has identified that naturally occurring granivores can be used as a weed management tool.