Timing of Avian Migration Onset Through the Oklahoma City Area 1995-2017 Using NOAA Weather Data

Abstract

Avian migration timing and duration may be linked to large-scale climate patterns and reflect shifts in average global temperatures. The National Centers for Environmental Information (NCEI) provides an archive of NOAA weather radar data scans occurring every ten minutes dating back to 1995. Our primary data of interest are 1) reflectivity and 2) radial velocity. Aerial density and flight direction were collected for available years and compared to global temperatures to examine seasonal migration effects. We used KTLX (OKC) weather radar data to determine time, duration, intensity and direction of seasonal avian migrations. Fall migrations began in September and spring migrations in March between 1995-2017, while the global average temperature steadily increased by 2.358 ?C. Fall migration trended toward later onset dates, while Spring migration trended toward earlier. Fall migration onset exhibits a stronger positive relationship with temperature than spring, potentially because inter-year March temperature patterns vary more than those of September. Ground truthing of radar data using eBird sightings revealed large-scale migratory events into Oklahoma during the second week of the fall migratory period. Comparatively, in spring migration there were constant departures from the region over the first five weeks of migration. This continuous rate of departures over time may also contribute to the weaker relationship between migratory onset and temperature in the spring.