Using Continuous-time Multistate Modeling to Analyze Dominance Hierarchies of C. anna
Author: Elizabeth Mathiasen
Faculty Supervisor: Derrick Groom
Department: Biology
Changes in dominance hierarchies in communities of hummingbirds are highly complex and can rapidly change over short time scales. These changes are shaped by a variety of forces, including phenotypic traits, community composition and environmental factors. I aim to explore what biotic and abiotic factors are related to changes in dominance over time, and how territory displacement affects other nearby resources in a community. I hypothesize that sex, plumage characteristics, age, and season will impact territory dominance and vagrancy, with older, larger, and more male-like birds being more dominant over younger, smaller species and females. I also hypothesize that an individual’s displacement from one area will impact adjacent areas. From 2016 to 2021, 604 Anna’s hummingbirds (Calypte anna) and black-chinned hummingbirds (Archilochus alexandri) were PIT-tagged, then released to use feeders equipped with RFID-chip readers at a site in Winters, CA. At time of capture, each bird was identified by species, sex, and age, and the proportion of plumage iridescence was scored. Dominant individuals will be determined by the proportion of total visits to each feeder by each bird, with individuals having the greatest proportion of feeding events at a feeder identified as dominant. A multi-state modeling approach will be employed to establish the probability of transition from a state of vagrancy to dominance and back, and covariates of sex, age, species, season, and plumage characteristics will be taken into consideration. Further work using this novel approach will examine additional factors that may influence dominance.