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).
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