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The spectrum of environmental signals known to influence reproduction in vertebrates is truly daunting. However, it is possible to classify these factors into three major types (Fig. 5.3, Wingfield 1980, 1983; Wingfield et al. 1999, note that the signals from unpredictable events are not included here). Initial predictive information (e.g. the annual change in day length) triggers the development phase of the reproductive life history stage, maintains mature capability and then regulates termination at the end of the breeding season (Fig. 5.3). Local predictive information (e.g. temperature, food supply, rainfall) may inhibit or accelerate effects of initial predictive information. These cues are also important to time onset of actual nesting at mature capability, and adjust timing of the termination phase (Fig. 5.3). All social interactions are clustered under synchronizing and integrating information that can influence the development phase and support functions such as territorial behavior, synchronize mates as they begin nesting and integrate transitions between sub-phases such as sexual to parental behavior (Wingfield 2006, Fig. 5.3).