Susan McRae

Research Interests

I am broadly interested in the evolution of sociality. Social systems are the products of behavioral strategies of individuals. I study how conflicts of interest arising from group-living are resolved through the evolution of alternative behavioral strategies. My studies have focused on parent-offspring conflict, reproductive parasitism, and other conflicts arising from sociality. I am particularly interested in how ecological, social and genetic factors interact in shaping the evolution of parasitic and cooperative breeding strategies. Measuring kinship is fundamental to understanding conflicts of interest. My research integrates field observation and experimental work on populations of marked individuals with molecular genetic determination of relatedness. In one project, I study how ecological factors affect the evolution of conspecific brood parasitism in the common moorhen. Host responses to brood parasitism are expected to vary in relation to the risk of parasitism and the cost of parasitism to the host. One principal question is: Among populations with varying rates of conspecific brood parasitism, are host responses predictable from ecological, genetic and social factors?

Behavior and evolution of female mimic ruff sandpipers

Since 2006, I have collaborated with David Lank (Simon Fraser University, Canada) investigating the evolution and behavior of female mimics among ruff sandpipers. Male ruff sandpipers come in three flavors: Independents with dark ruff plumages, defend territories (courts) on the mating arena, Satellites with white ruff plumages move among these courts and co-display, while Faeders (female mimics) are smaller, have female-like plumage and behave as sneakers. We conducted breeding experiments in aviaries at Simon Fraser University to look at the behavior and evolution of this morph. Collaborating with colleagues from the U.K. working on the genomics of ruff morphs, we discovered that the genetic basis for these extraordinary reproductive strategies is a chromosomal inversion or ‘supergene’.

Conservation is a strong motivation for my research, and I am becoming increasingly involved in local avian projects (see below) and through ECU’s agreement with Sylvan Heights Bird Park.

King Rail Conservation Project

Since 2011, my students and I have been studying King Rails Rallus elegans, a rare and declining secretive marshbird. Wetlands are among the most productive ecosystems and provide habitat for up to 85% of North America’s migratory bird species. Wetland destruction across much of the King Rail’s range has led to the decline of this and other marsh bird populations. The King Rail is the fastest declining hunted rail species, listed in the North American Conservation Action Plan as a species of ‘high concern’, and globally as ‘Near Threatened’ by BirdLife International. Due to the bird’s secretive nature, infrequent vocalizations, cryptic plumage, and occupancy of densely vegetated wetlands, little is known about the King Rail’s behavior, demography or habitat use. We have begun to redress this by studying a breeding population at Mackay Island National Wildlife Refuge. Though making inferences about population size, dispersal, recruitment, and survival rates is challenging, we have been making inroads through a combination of field monitoring and experiments, complemented by genetic analysis of population structure.

Behavior, Ecology and Genetics of the Eastern Bluebird

Since 2010, my students and I have been monitoring Eastern Bluebirds nesting at ECU’s West Research Campus. We are examining long-term seasonal trends in reproductive success, and life history variables (timing of breeding, clutch size, hatching and fledging rates), as well as site fidelity and recruitment. Becoming a field assistant on this project is an excellent way for undergraduates to learn techniques in field ornithology. Several students have developed their own Honors Thesis projects on this system. Interested biology majors are encouraged to inquire, but please only do so if you are willing to commit to working on the project during through the summer semesters. In part, this is a conservation project as well: Eastern Bluebird populations are coming back having declined. They are limited by breeding sites due to shortage of nest cavities and competition from introduced European Starlings. We use ‘Homes for Bluebirds’ (Bailey, NC) nest boxes that are built to exclude starlings and cowbirds.