Winter Bird Migration Observed by WSR-88D Radar in the Vicinity of the Great Salt Lake, Utah

Annual damage to aircraft due to collisions with birds and biases in meteorological radar data provide significant reasons to study bird migration patterns. Limited analysis of bird migration events has been performed for the Great Salt Lake, Utah area. Furthermore, the migration events observed by radar in the vicinity of the Great Salt Lake during this study have several notable differences than previous radar studies which have primarily focused on songbird migrations. The current study investigates migration events, specifically of the tundra swan and other waterfowl, in the vicinity of the Great Salt Lake using Weather Surveillance Radar-1988 Doppler (WSR-88D) data from Salt Lake City, Utah (KMTX). A total of 277 migration events were identified in the months of November through January for the winters of 1997/98 through 2009/10. Three classifications were determined based on the evolution of radar reflectivity patterns using WSR-88D level II and level III data. Each event was defined as concentrated, widespread, or combination. Nearly all migration events observed by radar had start times between 0000 and 0200 UTC and durations of less than 2 hours. Of the 13 winters examined, there was an average of 21 events per winter, with a 2009/10 minimum of 12 events and a 2002/03 maximum of 38 events. The largest frequency of migration events were observed during the month of December. The months of November and January had approximately 57% and 27% of the frequency observed in December, respectively. In order to further relate migration findings to meteorological conditions, atmospheric soundings and surface observations were analyzed for the Salt Lake City, Utah area, for both event and non – event days. Our presentation will provide information regarding the influence that environmental parameters, such as wind speed and direction, visibility, precipitation, and temperature, had on Great Salt Lake bird migration events.