Rachel T. (Bru) Bolus

Photo of Rachel Bolus

PhD Candidate

B.S., University of Southern Mississippi, 2002
M.S., University of Southern Mississippi, 2005

Advisor: Bruce Byers
Dissertation/thesis title: Birdsong as a source of social information for migrating common yellowthroats

Research Interests

Every spring, migrant birds travel from the tropics to their breeding grounds in temperate North America. This long distance trip is punctuated by frequent stopovers, when birds need to forage, rest, and avoid predators. Birds must solve these problems efficiently to survive migration, yet many songbirds do not show annual stopover fidelity, meaning that each new stopover site is unfamiliar. Therefore, migrants must explore each unfamiliar stopover site, and any cues that decrease search times for food and safe roosting sites are beneficial. It is adaptive for birds to attend to cues that direct them to needed resources. For songbirds, social cues, especially song, seem particularly relevant. During spring migration, there is a cacophony of available information, as local breeding songbirds sing at high rates, advertising for mates and setting up breeding territories. My hypothesis is that migrant birds assess the distribution of resources at an unfamiliar stopover site by listening for the presence of local birds and then eavesdropping on their song interactions.

I am testing this hypothesis by trying to answer two basic questions: 1) Can song characteristics predict habitat structure, male quality, and/or insect abundance?, and 2) Do migrants respond to this information? I am attempting to answer the first question with an observational study, including recording song, measuring habitat, sampling insects, and capturing and measuring individuals. To address the second question, I will perform a playback experiment during migration, trying to lure migrants temporarily into unsuitable habitat with broadcast song that is predictive of quality habitat.

My focal species for this work is the common yellowthroat, Geothlypis trichas. I have two study sites: a power cut in East Leverett, Massachusetts, and in Lackawanna County, Pennsylvania at the field site of Dr. Robert Smith (The University of Scranton), Dr. Margret Hatch (Penn State Worthington Scranton), and Dr. Michael Carey (The University of Scranton).

In addition to social information use during migration, I am also interested in the effects of migration on the evolution of song. I am performing a dialect analysis on the common yellowthroat to explore the effects of migration and dispersal on dialects in this species. I am also analyzing common yellowthroat dialects because I am interested in estimating the song variation that a typical migrant can expect to encounter en route, thinking that this variation may influence migrant response to song.

Long distance migration is an inherently costly behavior that has been complicated by the fragmentation of suitable habitats that has been caused by human development. A better understanding of how migrants use information to locate and choose quality habitat is important for informed conservation decisions.


Owen, J., F. Moore, N. Panella, E. Edwards, R. Bru, M. Hughes, and N. Komar. 2006. Migrating birds as dispersal vehicles of West Nile Virus Ecohealth 3(2): 79-85.