EEB386H1 Study Guide - Final Guide: Character Displacement, Harriet Hemenway, Precocial
19 Apr 2015
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Lecture 6: life cycles: most birds are long day breeders. Long-day breeding refers to the instincts of mating when the days are long (i. e. in the summer). Most mammals are short-day breeders and mate during short days in the winter. This is because their gestation is much longer than in aves. Proximate causes of seasonal breeding are changes in photoperiod, rainfall, temperature, and social cue. Ultimate causes have the most selective pressures on breeding seasonality since birds need to coordinate raising their chicks with when food is the most abundant. A phenological mismatch can occur when climate change alters the timing of two different life cycles, of which at least one species relies on the other. For example, the great tit previously (1980 and before) had its period of matching the time of raising their hatchlings with the peak biomass of caterpillars (to raise hatchlings on).
