Weather and eared grebe winter migration near the Great Salt Lake, Utah
This study provides insight from the use of weather radar observations to understand the characteristics of the eared grebe migration near the Great Salt Lake (GSL) and provides unique information on weather conditions connected to these migration events. Doppler weather radar measurements from the Salt Lake City, Utah WSR-88D radar site (KMTX), along with meteorological surface and rawinsonde data, were used to identify and examine 281 eared grebe migration events across 15 winters from 1997/1998 through 2011/2012. An average of about 19 migration events occurred each winter with considerable interannual variability, as well as large variance in the spatial area and number of birds departing the GSL during each event. The migration events typically occurred during clear sky conditions in the presence of surface high pressure and colder than average surface temperatures. Migration events began 55 min after sunset, on average across the winter seasons, and in one case we demonstrate that an extended, nonstop flight was initiated of the departing eared grebes to northern Mexico. Eared grebes leaving the GSL largely flew above the freezing level with a mean northerly tailwind at flight altitude of 3.1 m s−1 and a westerly, cross-flight wind of 5.0 m s−1 while having an average flight speed at cruising altitude of 16.9 m s−1, or 61 km h−1. In addition to determining the variability of meteorological conditions during migration events across the 15 winters, atmospheric conditions during the largest migration event observed are presented and discussed.
KeywordsWeather Migration Radar Waterfowl Eared grebe Great Salt Lake
Much of this research was conducted during the 2010 Hobart and William Smith Colleges Summer Research Program and the 2012/2013 academic year as the first author’s senior undergraduate Honors research project. This work greatly benefited from discussions with Dr. Joseph Jehl and the efforts provided by Ms. Jennifer Hanger. The authors also thank Drs. Mark Deutschlander, Eric Hoffman, Nicholas Metz, Robert Beason, Mark Olivieri, and James Steenburgh whose expertise, comments, and suggestions greatly improved the work.
This work was partially funded by the Hobart and William Smith Colleges Environmental Studies Grant, the Hobart and William Smith Colleges Kloman Fund grant, and the Rochester Academy of Sciences.
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