Daylength determines departure date of the Spotted Flycatcher Muscicapa striata from its winter quarters.

The annual arrival and departure dates of the Spotted Flycatcher Muscicapa striata at Bloemfontein in the Orange Free State, South Africa, were noted for a continuous period of 36 years (1950-1986). According to a stepwise regression analysis, daylength is by far the most important environmental factor influencing the date of departure. The influence of the minimum, maximum and mean daily temperatures, duration of sunshine, rainfall and wind speed seems to be unimportant in this context.

Kok OB., Van Ee C.A. & Nel D.G., ARDEA 79 (1): 63-66.