Helen Sofaer, Katie Langin, and Jongmin Yoon
Faculty advice from Cameron Ghalambor
Ecology Active Learning Module Outline
Life-history evolution seeks to explain the incredible variation in reproductive strategies
that we observe in nature. In our research, we are using Orange-crowned Warblers (Vermivora
celata) as a model system to understand the ecological factors that affect avian life-histories, and
we will build an active learning module based on our research results. In this module, we will
focus on the effects of a visually-oriented nest predator on the reproductive behavior of birds,
specifically their nest visitation rates and nest placement. Parental activity at nests can increase
the probability of predation by visually-oriented predators (like jays and red squirrels), so birds
are expected to have lower nest visitation rates in the presence of these predators. Since previous
studies have found that avian nest predators are more likely to predate higher nests, we would
also expect birds to build lower and perhaps better concealed nests in areas where these predators
are present. As part of our research, we are comparing warblers breeding on adjacent islands,
where one island has an endemic scrub-jay that is an important visually-oriented nest predator
(Santa Cruz Island, CA), and the other island lacks visually-oriented nest predators (Catalina
Island, CA). Our research suggests that warblers on Catalina Island (1) build higher nests and (2)
feed their young at a higher rate, providing a simple model system to understand predator-prey
relationships. Life-history evolution is a fundamental concept in ecology and evolutionary
biology because it seeks to explain how ecological factors affect the diversification of life.
Further, this project will also highlight predator-prey interactions, especially the indirect effects
of predation (i.e. those not leading to prey death), which have traditionally received little
attention in introductory ecology courses.
Our module will be a web-based tool that introduces students to life history evolution and
our study system. We envision a series of linked web pages with the following content:
 Introductory page: A brief overview of life-histories and our study system and links to
subsequent pages.
 Summary of the effects of age-specific mortality rates on life-history evolution and
behavior, including the hypothesis that visually-oriented nest predators constrain nest
visitation rates. We will also have links to seminal and relevant papers from the primary
literature.
 Our study sites: We will provide general information on the Channel Islands of southern
California, where our study sites are located, as well as specific information on Santa
Cruz and Catalina Islands, including the predator communities on each island. We will
also provide a brief synopsis of the methods we employ in the field to track the
reproductive behavior of individual birds. We will emphasize here that nest predation
rates are much higher on Santa Cruz, where the endemic jay is present.
 Nest videos: This page will have video clips of parents feeding nestlings, so that students
understand how feeding rate data are collected.
 Finally, we will have a page where students can download simulated data (based on our
actual observed patterns) and where we will give specific instructions about what is
expected for their project (see below). This page will also include a very brief summary
of introductory statistics and hypothesis testing, and links to external (e.g. wikipedia)
pages on regression, t-tests, and ANOVA where students without a strong background in
statistics can obtain additional information.
The students will be instructed to read the background material provided on our site, and
then download and analyze the data. We will include the following variables in our dataset:
island, year, territory ID, female age, male age, nest height, nest concealment, feeding rate, and
number of nestlings. Given these data, the students will be expected to address one question
regarding the reproductive behavior of Orange-crowned Warblers. For instance, they may
choose to ask: (1) Do parents feed at a higher rate on the island without the visually-oriented nest
predator?, (2) Do females build more conspicuous nests on Catalina (using nest height or nest
concealment as the variable of interest)?, or (3) Do parents feed at a lower rate when their nests
are higher or poorly concealed? We will not spell these questions out to them; rather, they will be
expected to develop an interesting question based on the background material and the data
available. We will ask them to address only one question to keep the reports short for grading
purposes.
We will simulate the data so that (1) feeding rates are higher on Catalina, (2) nest height
is higher on Catalina, and (3) feeding rates are negatively correlated with nest height on Santa
Cruz (with a predator) but are not related to nest height on Catalina (without a predator). We may
also include other additive effects on feeding rates (e.g. parental age, nestling number, nest
concealment) and/or include these variables without having them affect feeding rates. (We’d also
like some feedback on if students can be expected to be able to analyze and interpret a statistical
interaction.) We will provide an analysis of each of the potential effects to Joe and Indy, to serve
as a key for grading student assignments.
Students will be expected to turn in a short report that includes their data analysis and
interpretation and answers to specific questions. We envision requiring a short introduction
(<200 words) explaining their research hypothesis, why predators should affect reproductive
behavior, and what prediction(s) they made. We will ask students to provide short methods
section (<100 words), followed by their results which should include the relevant statistics and at
least one figure. Students will provide a brief conclusion (<100 words) that provides an
interpretation of their results and discusses how well the data conformed to their prediction(s).
We may also ask several short answer (<50 words) questions of a broader nature, such as: 1)
Some studies have shown that nest predators may increase in abundance in urban, suburban, and
fragmented environments. How should nest provisioning rates vary along a rural-urban gradient?
2) If clutch size differed between these two islands, on which island would you expect smaller
clutches? 3) If we studied two different populations that had and lacked an adult predator, how
would this change our results? Which population might have a larger clutch size? 4) Can we say
that the presence of the nest predator caused feeding rates to be lower? If so, why? If not, what
would we need to do to establish this effect?
Our goal for this exercise is to introduce students to ideas in life-history evolution,
predator-prey interactions, and behavioral ecology while giving them an opportunity to ask an
interesting question, analyze an ecological dataset, and interpret the significance of their results
in a broader context. By giving the students flexibility to develop their own research question,
we hope to provide them with an opportunity to think about and be creative with their analyses.