Understanding Variation in Habitat Use Among Orange-Crowned Warblers “Oreothlypis celata” in Central Arizona, USA

PhD Dissertation, Karolina Fierro

Classic habitat selection theory predicts that individuals will choose habitats that confer higher fitness. Yet, we see cases where individuals use habitats associated with low reproductive success, even if highly suitable habitat is available. Using a 20-year dataset of Orange-crowned warblers (Oreothlypis celata) in Arizona, I will examine first what factors determine territory suitability. Furthermore, I propose two hypotheses that might explain variation in territory use. My hypotheses state that low-quality individuals may not always experience low reproductive success, as the Ideal Despotic Distribution affirms, but instead might increase their fitness, and therefore the territory suitability, via two strategies. These low-quality individuals may use territories with 1) higher variation in the survival probability of multiple nest sites, which will increase the cumulative survival probability of the territory, and 2) higher variation in the survival probability of eggs, nestlings and fledglings, which may increase territory suitability. Hence, I suggest that natural selection may favor different habitat selection strategies in both high- and low-quality individuals that allow them to achieve similar fitness.

I started my first field season at the Coconino National Forest, Arizona, on May 2012. During three months, I collected preliminary data about the distribution of territories, interspecific interactions, and foraging strategies of my four ground-nesting bird species. My research proposal was approved by my doctoral committee in December 2013. I have been collecting data on survival probability of fledglings and carrying out my experiment in order to determine the cumulative survival probability of multiple nest sites within the territories. I started a new experiment last summer 2014 in order to test the Public Information hypothesis and have more data to publish the first chapter of my dissertation.