Influences of Seasonal Factors on the Activity Onset of the House Finch
1966
Enright, J. T.
In laboratory experiments, cold environmental temperature (2°C) caused male House Finches to awaken later, relative to "dawn," than warm temperatures (20°C) when day lengths (hours of light per cycle) were held constant. When temperature was held constant, greater day lengths also caused later awakening relative to "dawn." Extrapolation of these observations to field conditions suggests that seasonal changes in average temperature and day length may exert opposite influences on awakening time: the long days of spring would induce minimal "anticipation" of dawn, while the warmer temperatures would tend to counteract this influence. Additional circumstantial evidence suggests that reproductive maturity may also cause earlier awakening, relative to dawn, day length and temperature held constant.
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