A description of the general principles underlying Zebra Finch song is given in standardized terminology. Differences were looked for in songs produced in two different contexts: courtship song and undirected song. In more than 7 males (domesticated and wild ones), clear differences were found with respect to number of introductory elements, number of motifs, speed of performance, and rigidity in sequence, indicating two distinct song types. Motivational problems and the adaptive value are discussed.

No abstract

In opportunistic breeding species living in unpredictable environments, gonadal development and activation should be quite different from that in periodically breeding species, which live in a n environment with highly predictable changes. In Australian Zebra Finch females, bred in laboratories, the development during ontogeny was investigated. Body growth, ovarian weight, and the diameter of the largest follicle were recorded in birds 10 days to some years of age. A linear follicle growth pattern from 10 to 100 days is followed by a resting phase, during which the follicles remain in a medium-developed resting state. As soon as favorable conditions occur, a rapid logarithmic growth and yolk deposition starts, leading to ovulation within one to two weeks. Egg laying sometimes occurs as early as day 90. The ovary as a whole reaches a medium-developed resting state much later, but remains in this state even during long nonbreeding intervals.Compared with photoperiodically breeding species, for example Zonotrichia leucophrysgambelii, the Zebra Finch has the disadvantage of permanently keeping its gonads activated. Because of the lack of proximate factors, the Zebra Finch has to respond to the appearance of the ultimate factors as quickly as possible. Activation of fully regressed ovaries would take too much time, but starting from a medium-developed resting state allows ovulation in less than two weeks. In addition, no detectable refractory period reduces the capacity to respond. In the young this causes precocity.These peculiarities have been selected for by the sporadic and erratic rainfalls, which cause the unpredictability of breeding periods in several parts of Australia.

Female geladas draw the attention of males to their sexual state both by visual and vocal signals. In addition to visual cues our studies demonstrate that gelada females in oestrus use calls which are not uttered normally by anoestrous, pregnant or lactating females. A special call of the female indicates the climax of the copulation. Furthermore, individual recognition and the special meaning of these calls is indicated by playback experiments.

The effect of models differing in releasing quality is tested with respect to acoustical features of the directed song, and is compared to song not induced by releasers (so called “undirected song”). A gradual change of several parameters (for example number of introductory elements, number of motifs per strophe, speed of performance of the first motif) was found, indicating a gliding increase of intensity from song not releaser‐provoked, via song released by models poor in releasing stimuli to song induced by living females.