One factor limiting the population size of secondary cavity-nesting birds in ponderosa pine is the number of suitable nesting cavities. Snags in the pine forest provide a large number of species with nesting and roosting sites. To maintain secondary cavity nesters at their natural population level, a density of 5.2 snags per ha is recommended for mature ponderosa pine. # /

Two laboratory experiments were conducted that investigated the effects of a number of factors on performance using an on-display touch-entry system. Experiment 1 (n = 60) was carried out using a video display in a seated work station; horizontal angle of regard between the user and the display, size of the targets used, and gender were manipulated as factors. Experiment 2 (n = 72) was carried out in a standing work station; both horizontal and vertical angle of regard between the user and the display, presence or absence of optical parallax, and gender were manipulated as factors. Results showed that all of the factors affected how accurately the touch-entry system accepted the touches. Statistical simulation models were then constructed by computing system accuracy as a function of the size of tactual recognition field used to capture the touch. It was possible both to accommodate the variability in performance among users and to minimize the effects of the manipulated factors on performance. This was the outcome for both seated and standing work stations. Implications of these results for the design of touch-entry systems are discussed.

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