Greg Wann GDPE Masters Defense
Friday, April 6, 2012, 10:00 AM
Francis Clark Room, B215 NESB

Animals endemic to alpine habitats have been receiving increasing attention in recent years due to concerns over sensitivities of high elevation systems to climate warming. Long-term datasets are needed to assess trends in populations of alpine endemic species, but such datasets are rare, primarily due to logistical challenges that constrain data collection in these environments. Long-term datasets also provide critical information on impacts of altered climate because they span multiple decades under which climate varies. To accurately forecast or predict the impacts of warming on alpine animals, it is necessary to first understand how they have responded to warming in the past. Here, I present a demographic analysis on 43 years (1968-2010) of long-term data for the white-tailed ptarmigan (Lagopus leucura) at an alpine study site in central Colorado. Spring warming was found to advance breeding phenology an average of 10 days over the course of study, and temperature was found to be the primary factor in timing of nesting. Weather conditions experienced immediately post-hatch were found to have the strongest effects on reproductive success, with seasonal effects being of secondary importance. Both the number of rain days occurring post-hatch and warm and dry seasonal conditions were found to negatively correlate with reproductive success. Reproductive success declined from the mid-1970s through 2008, but the mechanism behind this decline is not entirely understood. Winter precipitation was the weather variable that had the strongest effect on survival of breeding age white-tailed ptarmigan, and survival was found to be lowered during years of low winter cumulative precipitation. Annual rates of population change were greatest during the first decade of study but tended to be lower during subsequent decades. The average annual rate of population change was close to one, but there was a high amount of variability among years, an indication of a highly stochastic environment. The weather variables that were found to most strongly negatively impact reproductive success and survival in white-tailed ptarmigan are expected to increase in coming decades. Warming summers are a concern given the potential impact on standing snowfields and the potential to reduce brood-rearing habitats. Higher temperatures in the winter may decrease snowpack which was found to negatively affect survival. I discuss the implications for future climate change on white-tailed ptarmigan, and further introduce some new modeling techniques that can be applied to multiple data sources for gaining better demographic estimates. Newly developed Bayesian methods using Markov chain Monte Carlo offer a promising analytical route to gaining better inference on the impacts of climate change to wildlife populations.

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Event Contact: Jeri Morgan can be reached at (970) 491-4373

Sponsored by the Graduate Degree Program in Ecology.