bThe breeding biology of the Reed Warbler Acrocephalus scirpaceus and the Reed Bunting Emberisa schoeniclus was studied at Oxwich Marsh, Gower, primarily during the summers of 1978 and 1879. Three marshland habitat types were identified, and the utilisation, feeding ecology and breeding success of both species in respect of these habitats was considered. In 'pure reed marshes' both species bred earlier, produced heavier young, were predated less and had higher nesting success (i.e. probability of a nest producing young) than those breeding in 'mixed marshes' and other areas. Invertebrates were collected in each habitat. Diptera accounted for a very high proportion of all potential prey items throughout the breeding season. Pure reed marshes produced more invertebrates than elsewhere, and overall peak abundance measured by numbers and biomass ocurred from mid-June to mid-July, coinciding with the time when most young of both species were in the nest. The diet of nestlings based on faecal analysis and hide observations showed Reed Warblers to be generalist feeders, with a similar diet in all habitats. Reed Buntings proved to be more specialist feeders, with a diet varying considerably between habitat types. Adults of both species foraged mostly in carr when nesting in pure reed marshes, whilst those from mixed marsh nests mostly utilized the marsh. Habitat selection in the Sedge Warbler Acrocephalus schoenobaenus was studied. A separate habitat classification was used, which indicated a preference for nesting in areas with a mixed dense vegetation matrix, consisting mostly of reed and bramble. These areas contained the highest densities of breeding pairs and were occupied first. Evidence was given to support the view that the plant species content within a breeding territory was less important than its vegetative complexity, which was measured and shown to be negatively correlated with settlement time.

Learning allows organisms to predict and prepare for events in the environment that are not sufficiently regular that responses to each situation could be genetically hardwired. A possible categorization of what can be learned is as follows: First, an animal may learn <I>that </I>an event is likely to happen. This means learning predictive relations between events, or the probability that an event A occurs with an event B, rather than independently. Second, they may form a representation of the magnitude of the event. Third, animals may learn <I>when</I> an event is likely to happen, the temporal relations between events. Fourth, they may acquire knowledge <I> where</I> something will happen, the spatial relations between events. The question arises whether these distinctions are merely convenient labels or reflect genuine differences between dissociable psychological variables and perhaps processes. The most widely accepted account of animal learning, associative learning theory, assumes that information from all these variables is collapsed into only a single output variable: the strength of an associative link. The theoretical framework of associative learning has predominantly been tested and developed within the domain of learning about predictive relationships between events, weighted by event relevance. The requirements for navigation through space are in some respects quite different. Animals can influence the rate and direction of their passage through space. In the two or three dimensions of space shortcuts and detours become possible. The computation of path length may require vector addition. Possible goals of computation will be considered and compared to data on the contents, acquisition and manipulation of spatial representations. The experimental part of this thesis concentrates on two aspects of information acquisition, landmark stability and blocking. Animals appear to weigh information from different sources according to two different and normally opposed criteria, accuracy and reliability. If discrepancy between two such sources is small, more weight will be given to the more accurate source of information, if the discrepancy is large more to the reliable source.

Developmental changes may affect aimed limb movements by altering limb mass, muscle strength and musculo-skeletal resistance or changing the position of a target on the body relative to the responding limb. Scratching movements following stimulation of wings by 5th instars and adult Schistocerca gregaria were compared before and after the imaginal moult, during which the wings increase in length and rotate, presenting different wing surfaces to external contact. The arrangement of mechanosensory hairs on the wings of 5th instars and adults was determined and associated with the development of scratching behaviour. The neuronal projections of mechanosensory hairs on the hind wing projected intersegmentally to anterior ventral association centre (aVAC) of the metathoracic ganglion and continued intersegmentally to the mesothoracic aVAC. Scratching movements accommodated developmental changes that occurred between the 5th instar and adulthood of S. gregaria. There was no change in movement characteristics between 5th instars and adults, indicating that developmental changes in the muscle strength, limb mass and musculo-skeletal resistance were compensated. Movements were appropriately aimed to accommodate the increase in wing size, and were associated with stimulation of tactile hairs on different wing surfaces in 5th instars and adults, implying different synaptic connections onto post-synaptic interneurones. Therefore, changes in limb mass, muscle strength and musculo-skeletal resistance due to growth are be compensated for, possible mechanism are proprioceptive reflexes and dynamic joint stiffness. Changes in target position caused by body growth may be facilitated by the development of new mechanosensory hairs and different synaptic connections onto postsynaptic interneurones. Wing rotation is likely to be accommodated by the intersegmental projections of wing hair afferents, and the convergence of hind wing and fore wing sensory signals.

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