Brown-headed Cowbird (Molothrus ater) Science Article 18
The breeding seasons of birds are usually timed so that the young are reared during aperiod of abundant food. At high latitudes nearly all small birds may nest within a weekor two of each other. In warmer temperate climates where plants grow and insects areactive for several months, the breeding seasons are longer, and different species may have different breeding seasons.
ROBERT B. PAYNE, The Condor 75:80-99, 1973