The relative influences of the following factors upon female's nestbox-oriented behavior and ovarian activity was studied in domesticated strains of budgerigars: (1) prior breeding experience, (2) the physical presence of a male, (3) typically male visible courtship behavior and (4) the presence of, and the opportunity to physically interact with, other pairs. Budgerigars are a non-nestbuilding, cavity-nesting species. The female's nestbox-oriented behavior and the various precopulatory and copulatory behaviors of both sexes were quantitatively recorded. Amounts of these per bird per hour were statistically analyzed. All females could hear all vocalizations, including courtship ones, made by 70 to 80 males. (1) In experiments concerning the relative influences of prior breeding experience and the presence of a sexually active male, the females of all experimental groups were exposed to equal amounts of male precopulatory and copulatory behaviors. Also, no group of females was more or less sexually receptive than another. In addition to hearing male vocal stimuli, interacting with a male seems to stimulate (a) more virgin females to perform nestbox-oriented behavior and lay eggs and (b) earlier oviposition by both virgin and experienced females, than does male vocal stimulation alone. Although, when caged alone, more experienced than virgin females performed nestbox-oriented behavior and laid eggs, there was no experiential difference in the speed of such reproductive responses by those females that did respond during testing. When caged with males, the number of virgin and experienced females stimulated to perform nestbox-oriented behavior and to develop an active ovary did not appreciably differ; however, experienced females showed a greater speed of such reproductive response than did virgins. (2) Prior breeding experience seems to prompt an earlier start of nestbox-oriented behavior in the presence of a male whereas the presence of a male stimulates both virgin and experienced females to begin repeated steady nestbox occupations sooner after they initially enter the box than they would when exposed only to male vocalizations. Later phases of nestbox-oriented behavior seem uninfluenced by either experiential factors or the presence of a sexually active male. Differences in the times of initial oviposition between virgin and experienced females caged either with or without a male may stem from these 2 different responses in the earlier phases of nestbox-oriented behavior elicited in experienced and virgin females by the presence of a male. (3) Comparisons of females of homosexual pairs, females of heterosexual pairs and females caged without a male indicate that it is most probably those actions performed typically by males, rather than the presence of a male per se, which promote ovarian development, ovulation and the later phases of nestbox-oriented behavior. However, the presence of a member of the opposite sex but not visible courtship actions seems to promote the initial occupation of the nestbox. (4) Additional factors accruing from placing several pairs together in a common cage which may inhibit or stimulate female nestbox-oriented behavior and ovarian development are discussed. Fewer females laid eggs or possessed a significantly developed ovary when caged together with other males and females than when caged separately with a male. This inhibitory effect of group caging conditions is most, if not solely, seen in connection with experienced females. Those which were prompted to lay eggs did so at times insignificantly different from those of females with similar prior breeding experience caged separately with a male. Experienced females, regardless of the number of other birds in the cage, laid eggs significantly sooner than did virgins.