Predicting Continental-Scale Bird Migration Routes from Landscape Parameters

William Winters, one of my GIST students, successfully filed his MS thesis last fall, in which he created proof-of-concept models for bird migration routes at the continental scale.  We developed the topic as a way to fill in a missing scale in the efforts to reduce mortality of birds at towers and buildings.  At the scale of the building and tower, mitigations are now available, including lights-out during migration, and changing the lighting scheme on towers.  But what locations are most likely to have high levels of birds during migration, outside those already known as migratory hotspots (e.g., Cape May)?

Put another way, what places on the landscape are especially bad for tall towers and buildings because they are likely to kill more birds?  Are there really fewer birds killed at obstructions in the western part of the Great Plains as the records in our 2012 PLoS ONE paper might suggest?

Residuals in tower height-mortality regression at communication towers (Longcore et al. 2012).

Residuals in tower height-mortality regression at communication towers (Longcore et al. 2012). Note that the towers along the Front Range of the Rockies killed fewer birds than expected.

I posed the question of whether one could model probable migratory routes using least-cost path analysis and a simple set of physical parameters for sets of known wintering and breeding grounds for Neotropical migrant birds.  William ran with it.

A least-cost corridor raster for Red-eyed Vireos migrating from the Northern Atlantic forest to South America.

A least-cost corridor raster for Red-eyed Vireos migrating from the Northern Atlantic forest to South America (Winters 2015).

After some careful thinking about resolution and projection, William settled upon topography (slope) as a metric of landscape resistance, along with wind and an additional resistance value for crossing the Gulf of Mexico. Then, using pairs of wintering and breeding grounds for Red-eyed Vireo, Kirtland’s Warbler, and Golden-cheeked Warbler, he developed models to predict northbound and southbound migration routes.

The resulting maps, which were the result of some experimentation and comparison with existing observations compiled for the species in the literature and on eBird provide proof-of-concept that one could develop maps for whole species by linking together known wintering and breeding grounds.

Fall and Spring migration routes predicted for Kirtland's Warbler from Michigan only.

Fall migration route predicted for Kirtland’s Warbler from Michigan only (Winters 2015).

The maps show that the least-cost paths for the spring and fall migrations might be different.  For example, the models for Red-eyed Vireos southbound from New England funnel through the Florida Peninsula in the Fall, and return via the Gulf Coast of Florida in the Spring.

To see the full thesis, including many more maps, visit the USC Library website at this link: Identifying areas of high risk for avian mortality by performing a least accumulated-cost analysis.

MS Thesis Recreates Historical Topography of Lower Ballona Watershed

MS Thesis Recreates Historical Topography of Lower Ballona Watershed

3D Visualization Models as a Tool for Reconstructing the Historical Landscape of the Ballona Watershed

Committee Chair: Travis Longcore | Committee Members: Yao-Yi Chiang, John Wilson

Ever-increasing demand on Earth’s finite natural resources and land requires environmental planners to employ informed and successful management of environments. Historical resources enhance environmental management by providing information to compare past landscapes to contemporary, urbanized states. In this study, heterogeneous historical resources were converted into GIS datasets to reconstruct the Ballona Creek watershed in Los Angeles, California as a three-dimensional (3D) model. To develop the 3D terrain, contour lines were extracted from early 20th century United States Geological Survey (USGS) topographic maps. Transforming contour lines into a Digital Elevation Models (DEM) enabled creation of 3D models to visualize the terrain of the Ballona Creek watershed before the region was heavily urbanized. To increase the effectiveness and functionality of these models, 3D vegetation and hydrography features were also added to the terrain to “paint a picture” of the historic extent of the Ballona Creek watershed. The historic 3D topography allowed calculation of elevation changes occurring over the last century to the Ballona Creek watershed and provided visualizations of previously reconstructed historical habitats. These visualizations and associated analyses comparing historic and current conditions provide a historical perspective for environmental planners to identify landscape changes and current trajectories of urbanized landscapes. These results suggest that 3D visualizations models, synthesized from an array of historical resources, can effectively deliver information about past landscapes to environmental planners, decision makers, and the public.