Life History Theory

A case study with the orange-crowned warbler

Why do some species live for decades while others only live for a year—or a week? Why do some organisms breed only once, while others breed many times? How much effort should parents invest into each reproductive attempt? It’s our curiosity about our world, and the diversity of species in it, that drives scientists to study life history theory. Species clearly use very different strategies: some, like annual grasses, live fast and die young, while others, like hardwood trees, live a long time and spread their reproductive effort over many years. But what about species like agaves or bamboo, which live a long time, storing up energy, and then reproduce all at once? What ecological conditions favor the evolution of that type of strategy? How do factors like survival and resource availability affect which reproductive strategies are most successful?

The study of life history strategies is a big scientific field, so here we’ll focus on one small part: understanding how food availability and nest predators affect parental investment in birds. This website summarizes research going on at CSU that compares two populations of orange-crowned warblers (Vermivora celata) that breed on the Channel Islands off the coast of southern California. The islands in question - Catalina and Santa Cruz - are in close proximity but differ with respect to their predator communities and relative levels of insect abundance. Our research makes use of these natural differences to ask how predators and food shape the life history strategies of birds.

 

Orange-crowned warbler foraging on scrub oaks in southern California (photo by M. Yoon).

The assignment associated with this module will involve some data analysis and will ask you to provide brief answers to a series of questions. We recommend reading the 'Background' and 'Study System' webpages before you proceed to the 'Assignment' page. Looking through the photos on the 'Fieldwork' page and watching the 'Nest Videos' will also give you a feel for how we collected some of the data you will analyze. Finally, you will find additional sources of information on the 'Resources' page.

We hope this ecology module will provide a useful introduction to life history theory, and an interesting peak into research at CSU!

Please proceed to the Background page.

 

CSU Ecology Module developed by Helen Sofaer, Katie Langin, and Jongmin Yoon (2008).