Some simple estimates of abundance (reference is Krebs, C. J., 1989, Ecological Methodology. Harper & Row, New York).
Jolly-Seber. Enters an array formula that computes the Jolly-Seber estimate of abundance (with confidence limits) based on counts in quadrats or transects. Because this is a dynamic formula, it can be used for a crude power analysis. Simply set out estimated counts in a column and enter the formula in a nearby cell. By testing different counts and sample sizes, you should be able to determine roughly how many quadrats are needed for an accurate population estimate.