[PAST EVENT] Vitek Jirinec - Thesis Defense - Biology

March 30, 2015
1pm - 2pm
Following the trend in many populations of migratory songbirds, the charismatic Wood Thrush has experienced long-term range-wide declines over the last few decades. A number of studies indicate that the species is area-sensitive: nest success and probability of occurrence decline with decreasing forest patch size. However, our five-year bird census in suburban and rural areas in coastal Virginia provides little evidence for decreased probability of occurrence in smaller forest fragments. Perhaps then, housing development per se is not necessarily detrimental to Wood Thrush, as long as certain habitat requirements are met. Although the species has been extensively researched, there is little information on why birds use a particular area, and knowledge of which environmental features explain concentrated bird use is therefore limited. This is a missed opportunity for identification of critical factors necessary for the conservation of this species. We captured and radio-tracked 37 male birds over two breeding seasons (2013, 2014) in tandem with vegetation and food prey availability sampling. Our models reveal bird activity increases with biomass of invertebrate prey and availability of certain habitat features. Bird presence is thus likely tied with access to these environmental factors, which are in turn affected by their own suite of predictors.

However, whether knowledge of bird habitat requirements derived from daytime-only observations is sufficient is necessarily contingent on birds using same areas at night. We therefore captured 10 female mates of 2014 males and examined roosting positions in relation to bird daytime home range, vegetation density, and nest status. Nocturnal tracking revealed a significant portion of male birds sleep outside their daytime home ranges in areas with higher vegetation density while females sleep on nests. However, without active nests, males guard females at night, presumably to ensure paternity during periods of female fertility. These results provide novel natural history information for this popular species, and provide additional tools for reversal of its population decline.

Vitek Jirinec is currently a graduate research assistant at the Biology Department, where he is working on his master's thesis on Wood Thrush movements in human-altered coastal Virginia using radio telemetry. Along with his advisor (Dr. Matthias Leu), he is involved with a number of projects, including long-term frog monitoring, avian point counts, as well as the effects of white-tailed deer on forest bird communities. Vitek received his undergraduate degree in Wildlife Biology at Humboldt State University in California, where he worked on ecosystem services and roosting behavior of migratory birds in Jamaican coffee farms. In the past, Vitek worked on bird projects in California's Sierra Nevada, Texas panhandle, Hawaii's Maui, Costa Rica, and Alaska's Arctic National Wildlife Refuge, among others.