Geographic Pattern of Population Change as a Key to Understanding Declines of Neotropical Migratory BirdsEPA Grant Number: R827406
Title: Geographic Pattern of Population Change as a Key to Understanding Declines of Neotropical Migratory Birds
Investigators: Maurer, Brian A. , Dennis, Brian , Lele, Subhash , Taper, Mark L.
Institution: Brigham Young University , Montana State University , The Johns Hopkins University , University of Idaho
EPA Project Officer: Hiscock, Michael
Project Period: July 1, 1999 through June 30, 2000
Project Amount: $133,621
RFA: Futures: Detecting the Early Signals (1999) RFA Text | Recipients Lists
Research Category: Water , Sustainability , Land and Waste Management , Ecosystems , Ecological Indicators/Assessment/Restoration
Description:The objectives of this project are: (1) review the existing research on migratory bird ecology and the threats of significant population declines, with the goal of determining the biological reliability of the results and the adequacy modeling and statistical protocols used to obtain them; (2) develop mechanistic modeling protocols with the goals of (i) understanding why declines are occurring in some species, but not in others, and (ii) examining the effect of observer variability and measurement errors on inferences drawn about populations; and (3) explore how to use these protocols to develop specific recommendations about management actions that might be undertaken to mitigate or reverse declines in species that are identified as likely candidates for further declines.
Approach:The review of existing research will focus on current literature to determine the extent to which species of birds that migrate to the Neotropics are declining. We will focus on studies that imply causal links between widespread environmental change on the breeding, migratory and winter habitats of these species. We will also develop mechanistic models that incorporate density dependence, spatial variation in maximum growth rates, and dispersal to explain the spatial pattern of population dynamics for selected species of Neotropical migrants. We will use Breeding Bird Survey (BBS) data to estimate the parameters of these models. Estimating model parameters, including the effects of observer error, will be done using maximum likelihood, composite likelihood and estimating equations. Estimates of model parameters will be used to calculate measures of extinction risk including geographic range size, time to extinction, and degree of fragmentation.
Expected Results:We anticipate identifying methods that go beyond current measures of population trends in species of Neotropical migratory birds by developing models with parameters that make specific statements about how, where and why populations are changing. We also will have some indications of the seriousness of observer variability in the BBS and steps that might be taken to account for it.
Improvement in Risk Assessment:
Our proposed measures of the relative risk of different species will produce scientifically defensible measures of risk. By incorporating mechanistic modeling protocols and accounting for observer error, we should be able to provide some general indication of the reliability of our estimates.