Winds aloft over three water bodies influence spring stopover distributions of migrating birds along the Gulf of Mexico coast

Migrating birds contend with dynamic wind conditions that ultimately
influence most aspects of their migration, from broad-scale movements to
individual decisions about where to rest and refuel. We used weather
surveillance radar data to measure spring stopover distributions of
northward migrating birds along the northern Gulf of Mexico coast and
found a strong influence of winds over non-adjacent water bodies, the
Caribbean Sea and Atlantic Ocean, along with the contiguous Gulf of
Mexico. Specifically, we quantified the relative influence of meridional
(north-south) and zonal (west-east) wind components over the three water
bodies on weekly spring stopover densities along western, central, and
eastern regions of the northern Gulf of Mexico coast. Winds over the
Caribbean Sea and Atlantic Ocean were just as, or more, influential than
winds over the Gulf of Mexico, with the highest stopover densities in the
central and eastern regions of the coast following the fastest winds from
the east over the Caribbean Sea. In contrast, stopover density along the
western region of the coast was most influenced by winds over the Gulf of
Mexico, with the highest densities following winds from the south. Our
results elucidate the important role of wind conditions over multiple
water bodies on region-wide stopover distributions and complement tracking
data showing Nearctic-Neotropical birds flying non-stop from South America
to the northern Gulf of Mexico coast. Smaller-bodied birds may be
particularly sensitive to prevailing wind conditions during non-stop
flights over water, with probable orientation and energetic consequences
that shape subsequent terrestrial stopover distributions. In the future,
the changing climate is likely to alter wind conditions associated with
migration, so birds that employ non-stop over-water flight strategies may
face growing challenges.