Military lands and waters may be particularly valuable for migrating birds requiring stopover habitat to rest and refuel en route to very distant seasonal ranges. Recent developments in radar technology have provided powerful tools for investigating on a broad scale migrant use of military installations, thus providing an opportunity to improve both conservation and flight safety measures. This research project developed a radar-based monitoring strategy for migratory birds on military lands. The broad goal was to investigate migrant use of military installations as stopover habitat using ground-based surveys and Doppler weather surveillance radar data (WSR-88D, also known as next generation radar [NEXRAD]).
Spring and fall migrant use of 40 military installations across the United States were qualitatively investigated. These times of year were selected because they are the periods when Bird Aircraft Strike Hazard (BASH) is of most concern. Migratory patterns on three installations (Eglin Air Force Base, Florida; Fort Polk, Louisiana; and Yuma Proving Ground, Arizona) were then closely examined, and migration forecast models for those locations were developed with the goal of providing a tool for reducing the probability of collisions between birds and military aircraft. A comparison was also made between radar estimates of migrant densities aloft during exodus events and more traditional ground-based surveys to evaluate the effectiveness of estimating migrant abundance in stopover habitat with radar data. At Fort Polk, movement ecology and migrant-habitat relations of the red-eyed vireo were investigated during migratory stopover. Lastly, migrant use of diverse riparian habitats was compared along water courses near the Yuma Proving Ground.
Results indicated that approximately half of the installations examined with radar data contained migrant stopover “hotspots,” reaffirming the fact that military installations are important to migrating birds. Interestingly, migrant abundances, and species turnover as estimated by ground-based surveys, were found to poorly reflect migrant densities estimated with radar data. Migrant abundance, species richness, and community composition were all also found to be influenced by riparian vegetation composition. This information collectively suggested that radar data can be used to identify migratory hotspots on military installations and improve flight safety on installations with an aviation mission. However, radar data may not be sufficient to distinguish fine-scale differences in habitat use by migrants within an installation’s boundaries.
Radar information showing bird migration on and near military installations is important for the protection of habitats used by migratory birds during stopover periods. This information is vital to Department of Defense land managers who protect stopover areas on military lands. Similarly, radar data are particularly important to land managers of military air stations where bird-wildlife/aircraft collisions threaten lives and cost millions of dollars in damages to aircraft infrastructure every year. By identifying where, when, how long, and in what concentrations migratory birds inhabit temporary stopover sites or pass above military training airspace, affected installations will be able to improve both military readiness and species conservation.