Using Weather Surveillance Radar to Understand trans-Gulf Migration EcologySubmitted by editor on 30 May 2023. Get the paper!
Figure 1: A scarlet tanager, one of many bird species that make nonstop overwater flights across the Gulf of Mexico during migration. Photo by Kyle Horton.
Each spring, billions of migratory birds travel from non-breeding grounds in Central and South America to breeding grounds in North America. As part of these migratory journeys, many birds will make non-stop crossings over the Gulf of Mexico, flying directly across the open water. Considering that most of these birds weigh no more than a few ounces, this is an impressive feat. As a result of these energetically taxing trans-Gulf flights, the northern Gulf coast region of the United States is critical for migratory birds, providing the first possible stopover habitat for migrants to rest and refuel prior to continuing their migrations.
However, migrating birds face a multitude of anthropogenic obstacles around the Gulf, including collisions with structures (especially buildings and wind turbines) and attraction to and disorientation from artificial light. The importance of this stopover habitat, as well as the high levels of human activity and corresponding anthropogenic effects in the Gulf region, highlight a high priority need for conservation.
Using weather surveillance radar data, we can quantify the timing and intensity of trans-Gulf migratory arrival along the Gulf coast, providing important knowledge to inform conservation efforts and fill current gaps in knowledge of migration ecology in the Gulf region. Here, we explored ten years of weather surveillance radar data from five sites along the northern Gulf of Mexico coast to quantify the daily and seasonal timing and intensity of arriving trans-Gulf migrants. On average, peak migration intensity occurred nine hours after local sunrise, occurring earliest at easternmost sites. In local time, these mean arrival times corresponded to mid to late afternoon, between 3 and 4 pm. Looking across the spring season, the greatest number of birds arrived between late April and early May, with peak intensity occurring latest at westernmost sites. Overall, intensity of migration across was greatest at the westernmost sites and decreased moving farther to the east.
Moving forward, we aim to integrate radar observations with atmospheric variables and begin to analyze the relationship between atmospheric conditions over the Gulf and the timing of migratory arrivals. This understanding can then be used to model and predict – in real-time – the timing of trans-Gulf arrivals on a day-by-day basis using existing weather forecasts. By providing details on when the greatest numbers of migratory birds will make landfall, a forecasting system for trans-Gulf arrival could be used to make targeted conservation efforts at peak times of migration. Given the widespread decline of migratory bird populations, using forecasting as a tool to protect migrants within the Gulf region is a crucial effort in supporting and conserving migratory bird populations.