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The number of species varies greatly among taxa. In birds, for example, the parvorder Passerida contains 3556 species while the Odontophorida (New World Quails) contains only six species. This uneven distribution of species among avian taxa is not random and therefore warrants an explanation. The behavioral drive hypothesis stipulates that the capacity for innovation, coupled with the rapid transmission of the behavioral novelty to conspecifics, may expose individuals to new selective pressures and help fix mutations that would otherwise not be expressed. This should lead to accelerated rates of evolution. I test this hypothesis by examining the link between behavioral flexibility and the number of species per taxon. I adopt a comparative approach and seek a general explanation of richness, thereby removing the traditional focus placed on the success of the songbirds and on their complex singing apparatus. I use two measures of flexibility, feeding innovation rate and relative brain size. (Abstract shortened by UMI.)

A model is presented which predicts the simultaneous searching strategy (walking speed) and diet choice of a terrestrial predator, assuming the behaviour is selected to maximize the net rate of energy gain The model predicts an inverse relationship between predator velocity and prey availability, independent of prey type, and that predators should stop foraging below a critical prey availability. It is predicted that diet choice should become more restricted with increases in the availability of highly profitable prey (ie net energy return per second spent handling) but broader with increases in the relative density of low profitability prey. Parameters of the model, prey availability, energy content and handling time were measured for the common prey of two estuarine wading birds - the Redshank (Tringa totanus L.) and the Oystercatcher (Heamatopus ostralegus L ) on the mid—estuarine Firth of Forth, Scotland. Predator energy expenditures whilst handling and searching for prey were estimated using radiotelemetry of the heart rate from six unrestrained Redshank in an outdoor aviary. At the lower critical temperature (16°C), the handling costs averaged l.9xBMR (Aschoff and Pohl 1971) and 2.OxBMR for pecking and probing respectively, whilst searching cost l.7xBMR (walking at 30cm.s-1). Observed walking speeds in both species were well matched with the model's predictions at medium and high encounter rates, but at low encounter rates (2 items m walked-1) were lower than predicted The critical low availability at which it is profitable to stop foraging did not occur in the field during the study period (February 1981-May 1982). In Redshank the observed diet was not consistent with the net energy maximization model in Autumn or Early and Late winter and instead fitted better a model of gross protein maximization. In spring the observed diet was best described by the maximization of net energy gain. Including costs had a significant effect on the diet predictions in the Redshank. Differences between predicted and observed diet choice in the Oystercatcher were a result of the underselection of very large, high profitability items and partial selection of low ranking prey. Including costs had no effect on the model's predictions for the Oystercatcher. Differences between model predictions and the observed behaviour are discussed In the 'prizing' Oystercatcher differences appeared to be a result of inaccuracy in collection of one of the model parameters (unsuccessful manipulation rates) and invalid assumptions concerning the discriminant abilities of the predator. Whilst conflicting selective pressures - protein requirements and the avoidance of bill damage, probably explain the deviations in Redshank and 'hammering' Oystercatchers respectively.

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1. This thesis presents the results of a population ecology study of the Dipper Cinclus cinclus in the western Ochil Hills, Tayside and Central Regions, Scotland between April 1985 and May 1988. 2. Particular attention was given to factors affecting juvenile survival between fledging and recruitment to the breeding population. These included investigation of the variation and significance of body size, plumage colour. dispersal distance, home range acquisition, dominance status and autumn body condition. 3. Overwinter survival was higher in adults than juveniles. Juvenile females had a greater overwinter survival and recruitment rate than juvenile males. Few body size measures were consistently associated with overwinter survival,though juvenile females with longer wings and tarsi tended to survive better. 4. Males had higher plumage brightness scores than females and, within sexes, adults were brighter than juveniles. Overall, survival overwinter and recruitment were not related to plumage brightness. 5. A laboratory test arena was developed for assessing dominance relations in small groups of temporarily captive birds. Social status between age and sex classes was correlated with plumage brightness. Within age classes, plumage brightness was a significant predictor of status in adults, but body size was more important in juveniles. 6. Females settled farther from their natal sites than males; most of this dispersal was completed soon after independence. The relationship between dispersal and dominance is discussed and a model developed. 7. Autumn population density was manipulated locally in a series of experimental juvenile introductions. Numbers rapidly returned to initial levels, though earlier released individuals persisted for longer. About 20% of introduced birds recruited, mainly higher status males. 8. Body composition of a small sample of birds collected between September and April is described. Lipid stores were greatest in winter and least in spring. A method for measuring pectoralis muscle thickness was developed using an ultrasound-based technique. 9. Condition indices derived from "ultrasound" measurements on live birds were used to evaluate the importance of protein reserves in overwinter survival. Males in good condition in autumn were more likely to recruit but no trend was apparent in females. 10. Two periods of high juvenile losses were identified: post-independence and late autumn. Predation could only be implicated in the former. The agent of late autumn losses was not proven but probably involved territorial intolerance and the consequent exclusion of subordinates to fringe habitats. It is concluded that density-dependent changes in mortality, related to dominance and mediated via dispersal, caused Dipper numbers tobe matched to available resources, principally food and breeding territories.

No description available.