Modeling Landscape-Scale Habitat Relations for Landbirds During Migration: Science Support for the Gulf Coast Joint Venture

Science Center Objects

USGS uses weather surveillance radar data and landscape-scale habitat metrics to model bird-habitat connections along the western coast of the Gulf of Mexico.

Millions of landbirds migrate through the Gulf of Mexico

Millions of landbirds migrate through the Gulf of Mexico

The Science Issue and Relevance: Millions of landbirds migrate through the Gulf of Mexico region each spring and autumn. Migration is energetically taxing, and these migrants depend on stopover habitats to provide the food and cover needed to complete their journey. For some species, as much as 85% of annual mortality occurs during migration. Stopover habitats in the Gulf of Mexico region have been lost or degraded due to the effects of development, agriculture, livestock grazing, timber industry activities, and the spread of exotic species. The continued loss or degradation of stopover habitat poses a risk to migrating birds; thus, knowing the location and landscape composition where peak numbers of birds consistently stop to rest and forage is critical for conservation planning. The Gulf Coast Joint Venture (GCJV) is dedicated to the protection and restoration of bird habitat along the gulf coast from Texas to Alabama.  One of the goals of the GCJV landbird conservation plan is to identify important stopover habitats and the landscape-scale habitat variables that influence migrant use of these areas.

Methodology for Addressing the Issue: We are using weather surveillance radar data and landscape-scale habitat metrics to model bird-habitat relations within 80 km of four radar stations along the western coast of the Gulf of Mexico. Collectively, the areas around the four stations (Brownsville, Corpus Christi, and Houston, TX and Lake Charles, LA) cover many of the coastal DOI-managed lands and state conservation areas from the Rio Grande River, TX to the Atchafalaya Basin, LA. We quantified the distribution of landbirds during stopover by using reflectivity data collected during spring and fall migration 2008–2012. To characterize the landscape around stopover sites, we measured the percent cover and habitat patch characteristics of 11 land cover types (2006 Coastal Change Analysis Program Data). Landscape metrics also included the length of rivers and roads within 5 km of a stopover site, and the distance from a stopover site to the nearest developed area, river, and coastline. After exploratory analyses with ordinary least-squares and geographically-weighted regressions, we will use structural equation modeling (SEM) to assess the relative strength and the direct and indirect nature of the causal relations among variables. Structural equation models will be estimated for each radar area and will provide a detailed understanding of landcape-scale habitat relations for migrant landbirds in the GCJV region.

Weather surveillance radar data and landscape-scale habitat metrics

Weather surveillance radar data and landscape-scale habitat metrics

Future Steps: Future research could incorporate the SEM models into an overall simulation model that explores migrant landbird response to habitat conservation and restoration, urban growth, climate change, hurricanes, and other factors that change the landscape within the GCJV region.