Inbound Arrivals: Using weather surveillance radar to quantify the timing of spring trans-Gulf bird migration - Data Set

Hundreds of millions of migratory songbirds cross the Gulf of Mexico each spring en route to breeding grounds in North America, making the northern Gulf coast a critical region for these migrants as it provides the first possible stopover location after a long, nonstop trans-Gulf crossing. However, this region has high levels of anthropogenic activity, making migrants vulnerable to a multitude of potentially lethal obstacles. Understanding the timing of mass migratory arrivals along the coast is imperative for advancing conservation of this critical region through the identification of key times in which to direct conservation actions (e.g., temporary halting of wind turbines, reduction of light pollution). To this end, we assessed 10 years of weather surveillance radar data from 5 sites along the northern Gulf of Mexico coast to quantify the daily timing and intensity of trans-Gulf migrant arrival. On a daily scale, we found that migrant intensity peaked an average of 9 hours after local sunrise, occurring earliest at furthest eastern regions of the Gulf. On a seasonal level, the greatest number of arrivals occurred between late April and early May, with peak intensity occurring latest at furthest west sites. Overall intensity of migration across all ten years of data was greatest at the most western sites and decreased the further east a site was located. These findings emphasize the use of the Gulf of Mexico region by migratory birds, providing information that can both advance our understanding of trans-Gulf migration and support conservation of migratory birds in this critical region. <strong>Data Set Key </strong> <strong>site</strong>: NEXRAD radar station ID <strong>deviance_explained</strong>: r2 value, the amount of variation explained by a generalized additive model with a response of migration intensity and a predictor of hour after sunrise. <strong>arrival_time:</strong> The time (hours after sunrise) in which migratory intensity was at its peak. <strong>peak_intensity</strong>: the peak of migration intensity measured on a given day as a value of eta - a measurement of radar reflectivity (i.e., the density of birds in the airspace). <strong>min_possible</strong> and <strong>max_possible</strong>: Range of data for a given day, the earliest and latest possible arrival time in hours after sunrise.