Multi-scale Effects of Forest Fragmentation and Landscape Context on Population Health of Birds

Working with Tom Martin and colleagues at the Montana Cooperative Wildlife Research Unit, we are evaluating population health of breeding birds in relation to forest fragmentation at 41 sites across the Lower 48 states. Data for these sites were contributed by a number of cooperators, both funded and unfunded, to the national BBIRD database, which currently contains roughly 40,000 nest records.

These data are from intensive studies of demography of birds at replicated sites and multiple spatial scales within and among geographic regions they will be used to assess spatial scale and landscape context effects on major population processes (nest predation and Brown-headed Cowbird parasitism) that influence population health of birds.

Our role at WSAL has been to prepare GIS databases, and from these data, to characterize the landscape context of BBIRD sites. We have mapped all BBIRD sites and plots and reviewed locations with cooperators, and assembled such GIS databases as land cover, elevation, hydrography, roads, and climate.

To date, analysis has focused on characterizing land cover (mapped by NLCD) within 1 km, 5 km, and 10 km of the plots for each BBIRD site, and within 50 km, 100 km, and 150 km of site centers. Fragmentation indices have been calculated using APACK software, and are being compared to nest success data in the BBIRD database.

To determine how well the BBIRD sites represent forest conditions across the Lower 48, we also have randomly selected 200 sets of sites and plots, and currently are calculating fragmentation indices within different radii for these random sets. Results will be compared with those for actual BBIRD sites.

Overall, data on nesting success of birds are being used to examine: 1) the spatial scales that influence demographic processes (i.e., predation and parasitism) within and among geographic regions, 2) the role of cover type (e.g., forest, agriculture, human habitations, etc) in the landscape (landscape context) on predation and parasitism relationships, and 3) predation and parasitism relationships with landscape characteristics among regions. We will use the information on predation and parasitism relationships obtained from these 3 sets of analyses to: 1) develop predictive models of bird demographic responses to forest fragmentation throughout North America, 2) examine the demographic consequences among functional groups (i.e., nest types, habitat requirements) to determine variation in population sensitivity and identify high risk species and species groups, and 3) model these demographic relationships in terms of population sustainability (i.e., is > 1.0) to attempt to identify landscape conditions that support source (self-sustaining) populations.

Results from this work will provide new and more general insight into the spatial scale influence of fragmentation and landscape context on nest predation and cowbird parasitism in birds. Moreover, results of this work can then be applied to satellite data across North America and across time to examine and predict the potential demographic consequences of land use changes on bird populations into the future.

Project completion date: September 30, 2003.