So far we've shown that predators, food and density are all factors that influence the reproductive success of Black-throated Blue Warblers at Hubbard Brook. But does that really make a difference to the total population size? Researchers testing this question found out that it does. Reproductive success during the breeding season in one year determines the number of yearlings – or first time parents - on the study plot the following year. This indicates that factors during the breeding season, particularly those that lower reproductive success, play an important role in determining the size of the warbler population.
Of course, environmental factors during the migratory and wintering periods are also important (in fact, they play a huge role in limiting survival of adults). However, this research does emphasize that changes in the environment affect the reproductive success and population size of Black-throated Blue Warblers.
|Learning module developed by K. Langin, H. Sofaer and S. Sillett for the Hubbard Brook Research Foundation (2009).|