The decline of many altricial species in temperate areas on land managed for agriculture is thought to be linked to changes in summer food availability, impacting on chick survival. This study specifically investigates the impacts of livestock grazing on the breeding performance of an insectivorous species, the meadow pipit (<i>Anthus pratensis)</i>, through the assessment of chick diet. Using conventional methods, adults are found to feed chicks a wide range of prey taxa. The significance of this diversity is shown by improved chick growth, emphasising an important link between diet and chick survival. Changes in the diets fed to chicks, as measured by conventional dietary methods, were observed in association with different intensities of grazing management. High stocking densities and also no livestock grazing resulted in a reduced biomass of invertebrates being fed to chicks. Conventional dietary analysis methods have a number of biases associated with them. Examining diet using three methods produced significantly different diet descriptions for meadow pipit chicks. The concept of using dietary markers was examined, which is increasingly becoming popular in ecological dietary studies. Lipids, namely hydrocarbons have been successfully established as faecal dietary markers in the examination of herbivore diet compositions. A range of hydrocarbons were extracted, identified and quantified from both invertebrate prey and bird faeces indicating the potential for this technique to assess bird diets, also highlighting areas of focus for future research. Hydrocarbon analysis was successfully used to show dietary changes occurring as result of grazing managements; therefore, this approach shows great potential as an ecological tool for assessing ecosystem changes as a result of human activities.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:439910 |
| Date | January 2006 |
| Creators | Stephen, Leigh |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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