You are here:
Calculations on the Back of an Envelope Model: Applying Seasonal Fecundity Models to Species’ Range Limits
Citation:
OLSEN, B. J., M. A. ETTERSON, AND R. GREENBERG. Calculations on the Back of an Envelope Model: Applying Seasonal Fecundity Models to Species’ Range Limits. Presented at International Society for Ecological Modelling (ISEM), Quebec City, QC, CANADA, October 06 - 09, 2009.
Impact/Purpose:
By investigating the direct effects of temperature or tidal flooding on seasonal fecundity, models like this one should more accurately predict the impact of climate change on bird reproduction and distributions.
Description:
Most predictions of the effect of climate change on species’ ranges are based on correlations between climate and current species’ distributions. These so-called envelope models may be a good first approximation, but we need demographically mechanistic models to incorporate the direct effects of factors likely to change in the face of climate change. New approaches to modeling seasonal fecundity may supply some of the necessary tools. Using a Markov chain framework, we developed a seasonal fecundity model of coastal plain swamp sparrows (Melospiza georgiana nigrescens) based on a detailed demographic study in the center of the bird’s range. We then combined this model with four parameterized geographic gradients in Emberizid demography to estimate swamp sparrow seasonal fecundity across a wide region of the Atlantic Coast of North America, including areas within and beyond the current range. By assuming that adult survivorship was equal to the value in the center of the range and solving for juvenile survivorship, we calculated geographically specific population growth rates across the Atlantic Coast. We assumed that the sparrow’s range would be described by the set of areas where population growth was greater than or equal to one. The predicted location of maximum population growth was in the center of the actual range, 37km from our detailed study location, and the predicted range boundary was 50km from the known breeding limit. By investigating the direct effects of temperature or tidal flooding on seasonal fecundity, models like this one should more accurately predict the impact of climate change on bird reproduction and distributions.