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Decision making is a framework we impose on a vast universe of possible behaviors to better understand the advantages and disadvantages of acting in different ways. Decisions under uncertainty are of particular interest because stochasticity is a feature of environments both today and throughout evolutionary history. As a result, we might expect decision makers (DMs) to have evolved mechanisms to handle variability. In this dissertation, I examine common decision processes in several model species: European starlings (Sturnus vulgaris), Banded tetras (Astyanax fasciatus) and humans (Homo sapiens). The broad range of approaches discussed include currencies DMs are expected to maximize (Risk Sensitivity Theory, Expected Utility), the currencies DMs do maximize (e.g. long versus short term rate maximizing models), the representation of outcomes in memory (Scalar Expectancy Theory) as well as explicit choice mechanisms (Sequential Choice Model). The first section of this thesis discusses responses to risk, offering humans and starlings choices between options which deliver certain or variable outcomes. Starlings demonstrate sensitivity to changes in the probability of variable outcomes and strong support for local rate maximization. Humans appear similarly sensitive to their own accuracy when task difficulty is varied. When the DM’s affective state was manipulated, neither humans nor starlings exhibit changes in risk preferences, but the effectiveness of these manipulations used could not be confirmed. Another topic of inquiry is the effect of the DM’s state at the time of valuation learning. State dependent valuation learning is demonstrated for the first time in a fish species, but Within Trial Contrast is not observed in starlings. Lastly, two experiments find strong support for the Sequential Choice Model, a promising new model of the mechanism of choice. Taken together, these experiments offer a glimpse into shared decision processes, but leave open questions about the mechanisms through which value is acquired.

In an effort to determine type, extent, and distribution of agricultural damage by blackbirds, county-wide damage appraisals were conducted in the fall of 1960. Crops checked included corn, peanuts, and milo. Based on the 96 fields examined throughout Nansemond County, the average monetary loss to the corn crop was slightly less than $.05 per acre. This loss can be reduced by planting a variety with a high degree of ear drooping and planting as early as possible. The peanuts appeared to be the crop most heavily damaged. An estimated 50 per cent of the crop was picked before blackbirds arrived. Of the part of the crop left exposed after the arrival of the blackbirds, only a small portion sustained damages amounting to above $5 per acre. By harvesting peanuts at an early date, losses to blackbirds can virtually be eliminated. The 1960 milo crop was not damaged by birds nearly so severely as previous crops were reported to have been. Anthracnose, a fungal disease, accounted for about 86 per cent of the damage previously called "bird damage." An estimated 15 per cent of this crop was destroyed by anthracnose, insects, and birds. In the case of all three crops, it was noted that the first and most severe damage was to those fields nearest nesting and roosting habitat. / Master of Science

The main object of this study was to investigate the effects of predation by starlings (Sturnus vulgaris) on populations of the grass grub (Costelytra zealandica) in Canterbury, with the secondary objective of investigating the feasibility of life table studies of grass grub populations under Canterbury conditions. Study plots were established in four areas, two on non-irrigated pastureland at Lincoln and Weka Pass and two on irrigated pastureland at Winchmore. A third study plot was established at Winchmore in the second year of field work.